local variable 'messages' referenced before assignment

[SOLVED] Local Variable Referenced Before Assignment

Python treats variables referenced only inside a function as global variables. Any variable assigned to a function’s body is assumed to be a local variable unless explicitly declared as global.

Why Does This Error Occur?

Unboundlocalerror: local variable referenced before assignment occurs when a variable is used before its created. Python does not have the concept of variable declarations. Hence it searches for the variable whenever used. When not found, it throws the error.

Before we hop into the solutions, let’s have a look at what is the global and local variables.

Local Variable Declarations vs. Global Variable Declarations

Local Variable Referenced Before Assignment Error with Explanation

Try these examples yourself using our Online Compiler.

Let’s look at the following function:

Explanation

The variable myVar has been assigned a value twice. Once before the declaration of myFunction and within myFunction itself.

Using Global Variables

Passing the variable as global allows the function to recognize the variable outside the function.

Create Functions that Take in Parameters

Instead of initializing myVar as a global or local variable, it can be passed to the function as a parameter. This removes the need to create a variable in memory.

UnboundLocalError: local variable ‘DISTRO_NAME’

This error may occur when trying to launch the Anaconda Navigator in Linux Systems.

Upon launching Anaconda Navigator, the opening screen freezes and doesn’t proceed to load.

Try and update your Anaconda Navigator with the following command.

If solution one doesn’t work, you have to edit a file located at

After finding and opening the Python file, make the following changes:

In the function on line 159, simply add the line:

DISTRO_NAME = None

Save the file and re-launch Anaconda Navigator.

DJANGO – Local Variable Referenced Before Assignment [Form]

The program takes information from a form filled out by a user. Accordingly, an email is sent using the information.

Upon running you get the following error:

We have created a class myForm that creates instances of Django forms. It extracts the user’s name, email, and message to be sent.

A function GetContact is created to use the information from the Django form and produce an email. It takes one request parameter. Prior to sending the email, the function verifies the validity of the form. Upon True , .get() function is passed to fetch the name, email, and message. Finally, the email sent via the send_mail function

Why does the error occur?

We are initializing form under the if request.method == “POST” condition statement. Using the GET request, our variable form doesn’t get defined.

Local variable Referenced before assignment but it is global

This is a common error that happens when we don’t provide a value to a variable and reference it. This can happen with local variables. Global variables can’t be assigned.

This error message is raised when a variable is referenced before it has been assigned a value within the local scope of a function, even though it is a global variable.

Here’s an example to help illustrate the problem:

In this example, x is a global variable that is defined outside of the function my_func(). However, when we try to print the value of x inside the function, we get a UnboundLocalError with the message “local variable ‘x’ referenced before assignment”.

This is because the += operator implicitly creates a local variable within the function’s scope, which shadows the global variable of the same name. Since we’re trying to access the value of x before it’s been assigned a value within the local scope, the interpreter raises an error.

To fix this, you can use the global keyword to explicitly refer to the global variable within the function’s scope:

However, in the above example, the global keyword tells Python that we want to modify the value of the global variable x, rather than creating a new local variable. This allows us to access and modify the global variable within the function’s scope, without causing any errors.

Local variable ‘version’ referenced before assignment ubuntu-drivers

This error occurs with Ubuntu version drivers. To solve this error, you can re-specify the version information and give a split as 2 –

Here, p_name means package name.

With the help of the threading module, you can avoid using global variables in multi-threading. Make sure you lock and release your threads correctly to avoid the race condition.

When a variable that is created locally is called before assigning, it results in Unbound Local Error in Python. The interpreter can’t track the variable.

Therefore, we have examined the local variable referenced before the assignment Exception in Python. The differences between a local and global variable declaration have been explained, and multiple solutions regarding the issue have been provided.

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Fix "local variable referenced before assignment" in Python

Introduction

If you're a Python developer, you've probably come across a variety of errors, like the "local variable referenced before assignment" error. This error can be a bit puzzling, especially for beginners and when it involves local/global variables.

Today, we'll explain this error, understand why it occurs, and see how you can fix it.

The "local variable referenced before assignment" Error

The "local variable referenced before assignment" error in Python is a common error that occurs when a local variable is referenced before it has been assigned a value. This error is a type of UnboundLocalError , which is raised when a local variable is referenced before it has been assigned in the local scope.

Here's a simple example:

Running this code will throw the "local variable 'x' referenced before assignment" error. This is because the variable x is referenced in the print(x) statement before it is assigned a value in the local scope of the foo function.

Even more confusing is when it involves global variables. For example, the following code also produces the error:

But wait, why does this also produce the error? Isn't x assigned before it's used in the say_hello function? The problem here is that x is a global variable when assigned "Hello ". However, in the say_hello function, it's a different local variable, which has not yet been assigned.

We'll see later in this Byte how you can fix these cases as well.

Fixing the Error: Initialization

One way to fix this error is to initialize the variable before using it. This ensures that the variable exists in the local scope before it is referenced.

Let's correct the error from our first example:

In this revised code, we initialize x with a value of 1 before printing it. Now, when you run the function, it will print 1 without any errors.

Fixing the Error: Global Keyword

Another way to fix this error, depending on your specific scenario, is by using the global keyword. This is especially useful when you want to use a global variable inside a function.

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Here's how:

In this snippet, we declare x as a global variable inside the function foo . This tells Python to look for x in the global scope, not the local one . Now, when you run the function, it will increment the global x by 1 and print 1 .

Similar Error: NameError

An error that's similar to the "local variable referenced before assignment" error is the NameError . This is raised when you try to use a variable or a function name that has not been defined yet.

Running this code will result in a NameError :

In this case, we're trying to print the value of y , but y has not been defined anywhere in the code. Hence, Python raises a NameError . This is similar in that we are trying to use an uninitialized/undefined variable, but the main difference is that we didn't try to initialize y anywhere else in our code.

Variable Scope in Python

Understanding the concept of variable scope can help avoid many common errors in Python, including the main error of interest in this Byte. But what exactly is variable scope?

In Python, variables have two types of scope - global and local. A variable declared inside a function is known as a local variable, while a variable declared outside a function is a global variable.

Consider this example:

In this code, x is a global variable, and y is a local variable. x can be accessed anywhere in the code, but y can only be accessed within my_function . Confusion surrounding this is one of the most common causes for the "variable referenced before assignment" error.

In this Byte, we've taken a look at the "local variable referenced before assignment" error and another similar error, NameError . We also delved into the concept of variable scope in Python, which is an important concept to understand to avoid these errors. If you're seeing one of these errors, check the scope of your variables and make sure they're being assigned before they're being used.

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Local variable referenced before assignment in Python

Last updated: Apr 8, 2024 Reading time · 4 min

# Local variable referenced before assignment in Python

The Python "UnboundLocalError: Local variable referenced before assignment" occurs when we reference a local variable before assigning a value to it in a function.

To solve the error, mark the variable as global in the function definition, e.g. global my_var .

Here is an example of how the error occurs.

We assign a value to the name variable in the function.

# Mark the variable as global to solve the error

To solve the error, mark the variable as global in your function definition.

If a variable is assigned a value in a function's body, it is a local variable unless explicitly declared as global .

# Local variables shadow global ones with the same name

You could reference the global name variable from inside the function but if you assign a value to the variable in the function's body, the local variable shadows the global one.

Accessing the name variable in the function is perfectly fine.

On the other hand, variables declared in a function cannot be accessed from the global scope.

The name variable is declared in the function, so trying to access it from outside causes an error.

Make sure you don't try to access the variable before using the global keyword, otherwise, you'd get the SyntaxError: name 'X' is used prior to global declaration error.

# Returning a value from the function instead

An alternative solution to using the global keyword is to return a value from the function and use the value to reassign the global variable.

We simply return the value that we eventually use to assign to the name global variable.

# Passing the global variable as an argument to the function

You should also consider passing the global variable as an argument to the function.

We passed the name global variable as an argument to the function.

If we assign a value to a variable in a function, the variable is assumed to be local unless explicitly declared as global .

# Assigning a value to a local variable from an outer scope

If you have a nested function and are trying to assign a value to the local variables from the outer function, use the nonlocal keyword.

The nonlocal keyword allows us to work with the local variables of enclosing functions.

Had we not used the nonlocal statement, the call to the print() function would have returned an empty string.

Printing the message variable on the last line of the function shows an empty string because the inner() function has its own scope.

Changing the value of the variable in the inner scope is not possible unless we use the nonlocal keyword.

Instead, the message variable in the inner function simply shadows the variable with the same name from the outer scope.

# Discussion

As shown in this section of the documentation, when you assign a value to a variable inside a function, the variable:

• Becomes local to the scope.
• Shadows any variables from the outer scope that have the same name.

The last line in the example function assigns a value to the name variable, marking it as a local variable and shadowing the name variable from the outer scope.

At the time the print(name) line runs, the name variable is not yet initialized, which causes the error.

The most intuitive way to solve the error is to use the global keyword.

The global keyword is used to indicate to Python that we are actually modifying the value of the name variable from the outer scope.

• If a variable is only referenced inside a function, it is implicitly global.
• If a variable is assigned a value inside a function's body, it is assumed to be local, unless explicitly marked as global .

If you want to read more about why this error occurs, check out [this section] ( this section ) of the docs.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• SyntaxError: name 'X' is used prior to global declaration

Borislav Hadzhiev

Web Developer

Copyright © 2024 Borislav Hadzhiev

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Python local variable referenced before assignment Solution

When you start introducing functions into your code, you’re bound to encounter an UnboundLocalError at some point. This error is raised when you try to use a variable before it has been assigned in the local context .

In this guide, we talk about what this error means and why it is raised. We walk through an example of this error in action to help you understand how you can solve it.

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What is unboundlocalerror: local variable referenced before assignment.

Trying to assign a value to a variable that does not have local scope can result in this error:

Python has a simple rule to determine the scope of a variable. If a variable is assigned in a function , that variable is local. This is because it is assumed that when you define a variable inside a function you only need to access it inside that function.

There are two variable scopes in Python: local and global. Global variables are accessible throughout an entire program; local variables are only accessible within the function in which they are originally defined.

Let’s take a look at how to solve this error.

An Example Scenario

We’re going to write a program that calculates the grade a student has earned in class.

We start by declaring two variables:

These variables store the numerical and letter grades a student has earned, respectively. By default, the value of “letter” is “F”. Next, we write a function that calculates a student’s letter grade based on their numerical grade using an “if” statement :

Finally, we call our function:

This line of code prints out the value returned by the calculate_grade() function to the console. We pass through one parameter into our function: numerical. This is the numerical value of the grade a student has earned.

Let’s run our code and see what happens:

An error has been raised.

The Solution

Our code returns an error because we reference “letter” before we assign it.

We have set the value of “numerical” to 42. Our if statement does not set a value for any grade over 50. This means that when we call our calculate_grade() function, our return statement does not know the value to which we are referring.

We do define “letter” at the start of our program. However, we define it in the global context. Python treats “return letter” as trying to return a local variable called “letter”, not a global variable.

We solve this problem in two ways. First, we can add an else statement to our code. This ensures we declare “letter” before we try to return it:

Let’s try to run our code again:

Our code successfully prints out the student’s grade.

If you are using an “if” statement where you declare a variable, you should make sure there is an “else” statement in place. This will make sure that even if none of your if statements evaluate to True, you can still set a value for the variable with which you are going to work.

Alternatively, we could use the “global” keyword to make our global keyword available in the local context in our calculate_grade() function. However, this approach is likely to lead to more confusing code and other issues. In general, variables should not be declared using “global” unless absolutely necessary . Your first, and main, port of call should always be to make sure that a variable is correctly defined.

In the example above, for instance, we did not check that the variable “letter” was defined in all use cases.

That’s it! We have fixed the local variable error in our code.

The UnboundLocalError: local variable referenced before assignment error is raised when you try to assign a value to a local variable before it has been declared. You can solve this error by ensuring that a local variable is declared before you assign it a value.

Now you’re ready to solve UnboundLocalError Python errors like a professional developer !

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How to Fix Local Variable Referenced Before Assignment Error in Python

Table of Contents

Fixing local variable referenced before assignment error.

In Python , when you try to reference a variable that hasn't yet been given a value (assigned), it will throw an error.

That error will look like this:

In this post, we'll see examples of what causes this and how to fix it.

Let's begin by looking at an example of this error:

If you run this code, you'll get

The issue is that in this line:

We are defining a local variable called value and then trying to use it before it has been assigned a value, instead of using the variable that we defined in the first line.

If we want to refer the variable that was defined in the first line, we can make use of the global keyword.

The global keyword is used to refer to a variable that is defined outside of a function.

Let's look at how using global can fix our issue here:

Global variables have global scope, so you can referenced them anywhere in your code, thus avoiding the error.

If you run this code, you'll get this output:

In this post, we learned at how to avoid the local variable referenced before assignment error in Python.

The error stems from trying to refer to a variable without an assigned value, so either make use of a global variable using the global keyword, or assign the variable a value before using it.

Thanks for reading!

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Python UnboundLocalError: local variable referenced before assignment

by Suf | Programming , Python , Tips

If you try to reference a local variable before assigning a value to it within the body of a function, you will encounter the UnboundLocalError: local variable referenced before assignment.

The preferable way to solve this error is to pass parameters to your function, for example:

Alternatively, you can declare the variable as global to access it while inside a function. For example,

This tutorial will go through the error in detail and how to solve it with code examples .

Table of contents

What is scope in python, unboundlocalerror: local variable referenced before assignment, solution #1: passing parameters to the function, solution #2: use global keyword, solution #1: include else statement, solution #2: use global keyword.

Scope refers to a variable being only available inside the region where it was created. A variable created inside a function belongs to the local scope of that function, and we can only use that variable inside that function.

A variable created in the main body of the Python code is a global variable and belongs to the global scope. Global variables are available within any scope, global and local.

UnboundLocalError occurs when we try to modify a variable defined as local before creating it. If we only need to read a variable within a function, we can do so without using the global keyword. Consider the following example that demonstrates a variable var created with global scope and accessed from test_func :

If we try to assign a value to var within test_func , the Python interpreter will raise the UnboundLocalError:

This error occurs because when we make an assignment to a variable in a scope, that variable becomes local to that scope and overrides any variable with the same name in the global or outer scope.

var +=1 is similar to var = var + 1 , therefore the Python interpreter should first read var , perform the addition and assign the value back to var .

var is a variable local to test_func , so the variable is read or referenced before we have assigned it. As a result, the Python interpreter raises the UnboundLocalError.

Example #1: Accessing a Local Variable

Let’s look at an example where we define a global variable number. We will use the increment_func to increase the numerical value of number by 1.

Let’s run the code to see what happens:

The error occurs because we tried to read a local variable before assigning a value to it.

We can solve this error by passing a parameter to increment_func . This solution is the preferred approach. Typically Python developers avoid declaring global variables unless they are necessary. Let’s look at the revised code:

We have assigned a value to number and passed it to the increment_func , which will resolve the UnboundLocalError. Let’s run the code to see the result:

We successfully printed the value to the console.

We also can solve this error by using the global keyword. The global statement tells the Python interpreter that inside increment_func , the variable number is a global variable even if we assign to it in increment_func . Let’s look at the revised code:

Let’s run the code to see the result:

Example #2: Function with if-elif statements

Let’s look at an example where we collect a score from a player of a game to rank their level of expertise. The variable we will use is called score and the calculate_level function takes in score as a parameter and returns a string containing the player’s level .

In the above code, we have a series of if-elif statements for assigning a string to the level variable. Let’s run the code to see what happens:

The error occurs because we input a score equal to 40 . The conditional statements in the function do not account for a value below 55 , therefore when we call the calculate_level function, Python will attempt to return level without any value assigned to it.

We can solve this error by completing the set of conditions with an else statement. The else statement will provide an assignment to level for all scores lower than 55 . Let’s look at the revised code:

In the above code, all scores below 55 are given the beginner level. Let’s run the code to see what happens:

We can also create a global variable level and then use the global keyword inside calculate_level . Using the global keyword will ensure that the variable is available in the local scope of the calculate_level function. Let’s look at the revised code.

In the above code, we put the global statement inside the function and at the beginning. Note that the “default” value of level is beginner and we do not include the else statement in the function. Let’s run the code to see the result:

Congratulations on reading to the end of this tutorial! The UnboundLocalError: local variable referenced before assignment occurs when you try to reference a local variable before assigning a value to it. Preferably, you can solve this error by passing parameters to your function. Alternatively, you can use the global keyword.

If you have if-elif statements in your code where you assign a value to a local variable and do not account for all outcomes, you may encounter this error. In which case, you must include an else statement to account for the missing outcome.

For further reading on Python code blocks and structure, go to the article: How to Solve Python IndentationError: unindent does not match any outer indentation level .

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UnboundLocalError Local variable Referenced Before Assignment in Python

Handling errors is an integral part of writing robust and reliable Python code. One common stumbling block that developers often encounter is the “UnboundLocalError” raised within a try-except block. This error can be perplexing for those unfamiliar with its nuances but fear not – in this article, we will delve into the intricacies of the UnboundLocalError and provide a comprehensive guide on how to effectively use try-except statements to resolve it.

What is UnboundLocalError Local variable Referenced Before Assignment in Python?

The UnboundLocalError occurs when a local variable is referenced before it has been assigned a value within a function or method. This error typically surfaces when utilizing try-except blocks to handle exceptions, creating a puzzle for developers trying to comprehend its origins and find a solution.

Why does UnboundLocalError: Local variable Referenced Before Assignment Occur?

below, are the reasons of occurring “Unboundlocalerror: Try Except Statements” in Python :

Variable Assignment Inside Try Block

Reassigning a global variable inside except block.

• Accessing a Variable Defined Inside an If Block

In the below code, example_function attempts to execute some_operation within a try-except block. If an exception occurs, it prints an error message. However, if no exception occurs, it prints the value of the variable result outside the try block, leading to an UnboundLocalError since result might not be defined if an exception was caught.

In below code , modify_global function attempts to increment the global variable global_var within a try block, but it raises an UnboundLocalError. This error occurs because the function treats global_var as a local variable due to the assignment operation within the try block.

Solution for UnboundLocalError Local variable Referenced Before Assignment

Below, are the approaches to solve “Unboundlocalerror: Try Except Statements”.

Initialize Variables Outside the Try Block

Avoid reassignment of global variables.

In modification to the example_function is correct. Initializing the variable result before the try block ensures that it exists even if an exception occurs within the try block. This helps prevent UnboundLocalError when trying to access result in the print statement outside the try block.

Below, code calculates a new value ( local_var ) based on the global variable and then prints both the local and global variables separately. It demonstrates that the global variable is accessed directly without being reassigned within the function.

In conclusion , To fix “UnboundLocalError” related to try-except statements, ensure that variables used within the try block are initialized before the try block starts. This can be achieved by declaring the variables with default values or assigning them None outside the try block. Additionally, when modifying global variables within a try block, use the `global` keyword to explicitly declare them.

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Local variable referenced before assignment: what it is and how to fix it

Local variable referenced before assignment

One of the most common errors in programming is to reference a local variable before it has been assigned a value. This can cause your program to crash or produce unexpected results.

In this article, we’ll discuss what a local variable is, why it’s important to assign values to local variables before you reference them, and how to fix errors caused by referencing a local variable before assignment.

We’ll also provide some tips for avoiding this error in the future.

What is a local variable?

A local variable is a variable that is declared within a function or block of code. Local variables are only visible within the function or block of code in which they are declared. This means that they cannot be accessed from outside of that function or block of code.

Why is it important to assign values to local variables before you reference them?

When you declare a local variable, you are essentially creating a placeholder for a value. The value of the local variable will be assigned when the function or block of code is executed.

If you try to reference a local variable before it has been assigned a value, your program will crash. This is because the compiler cannot determine what value to assign to the local variable.

How to fix errors caused by referencing a local variable before assignment

There are a few ways to fix errors caused by referencing a local variable before assignment.

• Assign a value to the local variable before you reference it. This is the simplest and most straightforward way to fix the error.
• Use the `const` keyword to declare the local variable. This will prevent you from accidentally assigning a value to the local variable.
• Use the `let` keyword to declare the local variable. This will allow you to assign a value to the local variable later in the function or block of code.

Tips for avoiding this error in the future

• Always assign a value to your local variables before you reference them. This is the best way to avoid this error.
• Use the `const` keyword to declare your local variables. This will help you to avoid accidentally assigning a value to the local variable.

|—|—|—| | Variable name | Line number | Description | | `x` | 10 | Variable is declared but not assigned a value before it is used. | | `y` | 15 | Variable is assigned a value after it is used. | | `z` | 20 | Variable is assigned a value before it is used. |

A local variable is a variable that is declared within a function or a block of code. It is only accessible within the scope of the function or block of code in which it is declared. This means that a local variable cannot be accessed outside of the function or block of code in which it is declared.

Local variables are used to store temporary values that are only needed within a specific function or block of code. This helps to keep the code organized and prevents variables from being accidentally overwritten.

What happens when a local variable is referenced before assignment?

When a local variable is referenced before assignment, a compiler error is generated. This is because the compiler cannot determine the value of the variable before it has been assigned a value.

For example, the following code will generate a compiler error:

int main() { int x; printf(“The value of x is %d\n”, x); }

The compiler error will be:

error: variable x is used uninitialized in this function [-Wuninitialized] printf(“The value of x is %d\n”, x);

The compiler error is telling us that the variable `x` is used uninitialized in the function `main()`. This means that the value of `x` has not been assigned before it is used in the `printf()` function.

How to avoid referencing a local variable before assignment

There are a few ways to avoid referencing a local variable before assignment.

• Assign a value to the variable before using it. This is the simplest way to avoid the error. For example, the following code will not generate a compiler error:

int main() { int x = 10; printf(“The value of x is %d\n”, x); }

• Declare the variable with the `extern` keyword. The `extern` keyword tells the compiler that the variable is defined in another file. This allows the compiler to determine the value of the variable even if it has not been assigned yet. For example, the following code will not generate a compiler error:

int main() { extern int x; printf(“The value of x is %d\n”, x); }

• Use the `volatile` keyword. The `volatile` keyword tells the compiler that the value of the variable can change at any time, even if it is not being used. This allows the compiler to avoid generating a compiler error for variables that are not being used. For example, the following code will not generate a compiler error:

int main() { volatile int x; printf(“The value of x is %d\n”, x); }

Local variables are a useful tool for storing temporary values. However, it is important to avoid referencing a local variable before assignment to avoid compiler errors. There are a few ways to avoid this error, such as assigning a value to the variable before using it, declaring the variable with the `extern` keyword, or using the `volatile` keyword.

What is a local variable referenced before assignment?

A local variable referenced before assignment is a variable that is used in a program before it has been assigned a value. This can cause errors, as the compiler cannot know what value the variable will have when it is used.

Why is it a problem to reference a local variable before assignment?

There are a few reasons why it is a problem to reference a local variable before assignment.

• It can cause errors. The compiler cannot know what value the variable will have when it is used, so it cannot check for errors such as division by zero or accessing an array out of bounds.
• It can make debugging difficult. If a program has a bug that is caused by a local variable being referenced before assignment, it can be difficult to track down the source of the bug.
• It can lead to security vulnerabilities. A local variable that is referenced before assignment can be used to store sensitive data, such as passwords or credit card numbers. This data could then be accessed by other parts of the program, or by an attacker who has gained access to the program.

How to avoid referencing a local variable before assignment?

• Initialize the variable to a default value. This is the simplest way to avoid the problem. For example, if you are declaring a variable of type `int`, you could initialize it to 0.
• Use the `const` keyword. The `const` keyword can be used to declare a variable as constant. This means that the variable can only be assigned a value once, and it cannot be changed after that.
• Use a `typedef`. A `typedef` can be used to create a new type that is based on an existing type. This can be useful if you want to create a type that cannot be assigned a value.

Examples of local variable referencing before assignment

The following are examples of local variable referencing before assignment:

int x = 10; // Error: variable ‘x’ is used before it is initialized

void foo() { int y = x; // Error: variable ‘x’ is not in scope }

In the first example, the variable `x` is used before it is initialized. This will cause an error at compile time.

In the second example, the variable `x` is used in the function `foo()`, but it is not declared in that function. This will also cause an error at compile time.

Referencing a local variable before assignment is a problem that can cause errors, make debugging difficult, and lead to security vulnerabilities. There are a few ways to avoid this problem, such as initializing the variable to a default value, using the `const` keyword, or using a `typedef`.

Q: What does it mean for a local variable to be referenced before assignment?

A: A local variable is a variable that is declared within a function or block of code. Local variables are not accessible outside of the function or block of code in which they are declared. When a local variable is referenced before it is assigned a value, this is known as a compile-time error .

Q: What are the consequences of referencing a local variable before assignment?

A: The consequences of referencing a local variable before assignment vary depending on the programming language. In some languages, the compiler will issue a warning or error. In other languages, the program may run, but the results will be unpredictable.

Q: How can I avoid referencing a local variable before assignment?

A: There are a few ways to avoid referencing a local variable before assignment.

• Declare the variable and assign it a value before you use it.
• Use a temporary variable to store the value of the local variable before you use it.
• Use a function to assign the value of the local variable.

Q: What are some common mistakes that can lead to referencing a local variable before assignment?

A: Some common mistakes that can lead to referencing a local variable before assignment include:

• Forgetting to initialize a local variable.
• Using a local variable in a conditional statement before it is assigned a value.
• Using a local variable in a loop before it is assigned a value.

Q: How can I debug a program that is referencing a local variable before assignment?

A: There are a few ways to debug a program that is referencing a local variable before assignment.

• Use a debugger to step through the code and watch the values of the local variables.
• Use a compiler flag to enable warnings or errors for uninitialized variables.
• Use a static analysis tool to scan the code for potential errors.

Q: What are some additional resources that I can refer to for more information on referencing local variables before assignment?

A: Here are some additional resources that you can refer to for more information on referencing local variables before assignment:

• [The C Programming Language](https://www.amazon.com/C-Programming-Language-2nd/dp/0131103628)
• [The C++ Programming Language](https://www.amazon.com/C-Plus-Plus-Programming-Language-4th/dp/0321563840)
• [The Java Programming Language](https://www.amazon.com/Java-Programming-Language-4th/dp/0134174858)

Here are some key takeaways:

• Local variables are initialized to the default value of their type when they are declared. This means that a local variable that is not assigned a value before it is used will contain the default value for its type.
• The default value for a variable depends on its type. For example, the default value for an integer variable is 0, and the default value for a boolean variable is false.
• Attempting to use a local variable that has not been assigned a value will result in a compiler error.
• You can avoid this error by assigning a value to a local variable before you use it. You can also use the `const` keyword to declare a local variable that cannot be changed after it is initialized.

By following these tips, you can help to ensure that your code is free of errors and that it runs as expected.

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How to Solve Error - Local Variable Referenced Before Assignment in Python

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• How to Solve Error - Local Variable …

Check the Variable Scope to Fix the local variable referenced before assignment Error in Python

Initialize the variable before use to fix the local variable referenced before assignment error in python, use conditional assignment to fix the local variable referenced before assignment error in python.

This article delves into various strategies to resolve the common local variable referenced before assignment error. By exploring methods such as checking variable scope, initializing variables before use, conditional assignments, and more, we aim to equip both novice and seasoned programmers with practical solutions.

Each method is dissected with examples, demonstrating how subtle changes in code can prevent this frequent error, enhancing the robustness and readability of your Python projects.

The local variable referenced before assignment occurs when some variable is referenced before assignment within a function’s body. The error usually occurs when the code is trying to access the global variable.

The primary purpose of managing variable scope is to ensure that variables are accessible where they are needed while maintaining code modularity and preventing unexpected modifications to global variables.

We can declare the variable as global using the global keyword in Python. Once the variable is declared global, the program can access the variable within a function, and no error will occur.

The below example code demonstrates the code scenario where the program will end up with the local variable referenced before assignment error.

In this example, my_var is a global variable. Inside update_var , we attempt to modify it without declaring its scope, leading to the Local Variable Referenced Before Assignment error.

We need to declare the my_var variable as global using the global keyword to resolve this error. The below example code demonstrates how the error can be resolved using the global keyword in the above code scenario.

In the corrected code, we use the global keyword to inform Python that my_var references the global variable.

When we first print my_var , it displays the original value from the global scope.

After assigning a new value to my_var , it updates the global variable, not a local one. This way, we effectively tell Python the scope of our variable, thus avoiding any conflicts between local and global variables with the same name.

Ensure that the variable is initialized with some value before using it. This can be done by assigning a default value to the variable at the beginning of the function or code block.

The main purpose of initializing variables before use is to ensure that they have a defined state before any operations are performed on them. This practice is not only crucial for avoiding the aforementioned error but also promotes writing clear and predictable code, which is essential in both simple scripts and complex applications.

In this example, the variable total is used in the function calculate_total without prior initialization, leading to the Local Variable Referenced Before Assignment error. The below example code demonstrates how the error can be resolved in the above code scenario.

In our corrected code, we initialize the variable total with 0 before using it in the loop. This ensures that when we start adding item values to total , it already has a defined state (in this case, 0).

This initialization is crucial because it provides a starting point for accumulation within the loop. Without this step, Python does not know the initial state of total , leading to the error.

Conditional assignment allows variables to be assigned values based on certain conditions or logical expressions. This method is particularly useful when a variable’s value depends on certain prerequisites or states, ensuring that a variable is always initialized before it’s used, thereby avoiding the common error.

In this example, message is only assigned within the if and elif blocks. If neither condition is met (as with guest ), the variable message remains uninitialized, leading to the Local Variable Referenced Before Assignment error when trying to print it.

The below example code demonstrates how the error can be resolved in the above code scenario.

In the revised code, we’ve included an else statement as part of our conditional logic. This guarantees that no matter what value user_type holds, the variable message will be assigned some value before it is used in the print function.

This conditional assignment ensures that the message is always initialized, thereby eliminating the possibility of encountering the Local Variable Referenced Before Assignment error.

Throughout this article, we have explored multiple approaches to address the Local Variable Referenced Before Assignment error in Python. From the nuances of variable scope to the effectiveness of initializations and conditional assignments, these strategies are instrumental in developing error-free code.

The key takeaway is the importance of understanding variable scope and initialization in Python. By applying these methods appropriately, programmers can not only resolve this specific error but also enhance the overall quality and maintainability of their code, making their programming journey smoother and more rewarding.

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4 ways to fix local variable referenced before assignment error in python, resolving the local variable referenced before assignment error in python.

Python is one of the world’s most popular programming languages due to its simplicity, readability, and versatility. Despite its many advantages, when coding in Python, one may encounter various errors, with the most common being the “local variable referenced before assignment” error.

Even the most experienced Python developers have encountered this error at some point in their programming career. In this article, we will look at four effective strategies for resolving the local variable referenced before assignment error in Python.

Strategy 1: Assigning a Value before Referencing

The first strategy is to assign a value to a variable before referencing it. The error occurs when the variable is referenced before it is assigned a value.

This problem can be avoided by initializing the variable before referencing it. For example, let us consider the snippet below:

In the snippet above, the variables x and y are not assigned values before they are referenced in the print statement. Therefore, we will get a local variable “referenced before assignment” error.

To resolve this error, we must initialize the variables before referencing them. We can avoid this error by assigning a value to x and y before they are referenced, as shown below:

Strategy 2: Using the Global Keyword

In Python, variables declared inside a function are considered local variables. Thus, they are separate from other variables declared outside of the function.

If we want to use a variable outside of the function, we must use the global keyword. Using the global keyword tells Python that you want to use the variable that was defined globally, not locally.

For example:

In the code snippet above, the global keyword tells Python to use the variable x defined outside of the function rather than a local variable named x . Thus, Python will output 30.

Strategy 3: Adding Input Parameters for Functions

Another way to avoid the local variable referenced before assignment error is by adding input parameters to functions.

In the code snippet above, x and y are variables that are passed into the add_numbers function as arguments.

This approach allows us to avoid the local variable referenced before assignment error because the variables are being passed into the function as input parameters.

Strategy 4: Initializing Variables before Loops or Conditionals

Finally, it’s also a good practice to initialize the variables before loops or conditionals.

If you are defining a variable within a loop, you must initialize it before the loop starts. This way, the variable already exists, and we can update the value inside the loop.

In the code snippet above, the variable sum has been initialized with the value of 0 before the loop runs. Thus, we can update and use the variable inside the loop.

In conclusion, the “local variable referenced before assignment” error is a common issue in Python. However, with the strategies discussed in this article, you can avoid the error and write clean Python code.

Remember to initialize your variables, use the global keyword, add input parameters in functions, and initialize variables before loops or conditionals. By following these techniques, your Python code will be error-free and much easier to manage.

In essence, this article has provided four key strategies for resolving the “local variable referenced before assignment” error that is common in Python. These strategies include initializing variables before referencing, using the global keyword, adding input parameters to functions, and initializing variables before loops or conditionals.

These techniques help to ensure clean code that is free from errors. By implementing these strategies, developers can improve their code quality and avoid time-wasting errors that can occur in their work.

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Python 3: UnboundLocalError: local variable referenced before assignment

This error occurs when you are trying to access a variable before it has been assigned a value. Here is an example of a code snippet that would raise this error:

Watch a video course Python - The Practical Guide

The error message will be:

In this example, the variable x is being accessed before it is assigned a value, which is causing the error. To fix this, you can either move the assignment of the variable x before the print statement, or give it an initial value before the print statement.

Both will work without any error.

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I get "UnboundLocalError: local variable referenced before assignment" error after using variable in defined function even after I define it

But whenever I run it I get the error:

Even though I assigned it the value of keepPlaying. I also assigned it 0 at the top to see if it fixed it. But no.

On the other hand, if I just run it without being a function, it works perfectly.

In case you need to know what I'm doing, I'm trying to making a simple game and this was to ask if the user wants to keep playing. While keepPlaying is "yes" it will repeat. I took the game out of the way to try to troubleshoot the bug.

(The full error message is here):

In case it matters I'm running the latest version of python for MacOS 10.15.7

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What is UnboundLocalError: local variable referenced before assignment?

Trying to assign a value to a variable that does not have local scope can result in this error:

Python has a simple rule to determine the scope of a variable. To clarify, a variable is assigned in a function, that variable is local. Because it is assumed that when you define a variable inside a function, you only need to access it inside that function.

There are two variable scopes in Python: local and global. Global variables are accessible throughout an entire program. Whereas, local variables are only accessible within the function in which they are originally defined.

An example of Local variable referenced before assignment

We’re going to write a program that calculates the grade a student has earned in class.

Firstly, we start by declaring two variables:

These variables store the numerical and letter grades a student has earned, respectively. By default, the value of “letter” is “F”. Then, we write a function that calculates a student’s letter grade based on their numerical grade using an “if” statement:

Finally, we call our function:

This line of code prints out the value returned by the  calculate_grade()  function to the console. We pass through one parameter into our function: numerical. This is the numerical value of the grade a student has earned.

Let’s run our code of Local variable referenced before assignment and see what happens:

Here is an error!

The Solution of Local variable referenced before assignment

The code returns an error: Unboundlocalerror local variable referenced before assignment because we reference “letter” before we assign it.

We have set the value of “numerical” to 42. Our  if  statement does not set a value for any grade over 50. This means that when we call our  calculate_grade()  function, our return statement does not know the value to which we are referring.

Moreover, we do define “letter” at the start of our program. However, we define it in the global context. Because Python treats “return letter” as trying to return a local variable called “letter”, not a global variable.

Therefore, this problem of variable referenced before assignment could be solved in two ways. Firstly, we can add an  else  statement to our code. This ensures we declare “letter” before we try to return it:

Let’s try to run our code again:

Our code successfully prints out the student’s grade. This approach is good because it lets us keep “letter” in the local context. To clarify, we could even remove the “letter = “F”” statement from the top of our code because we do not use it in the global context.

Alternatively, we could use the “global” keyword to make our global keyword available in the local context in our  calculate_grade()  function:

We use the “global” keyword at the start of our function.

This keyword changes the scope of our variable to a global variable. This means the “return” statement will no longer treat “letter” like a local variable. Let’s run our code. Our code returns: F.

The code works successfully! Let’s try it using a different grade number by setting the value of “numerical” to a new number:

Our code returns: B.

Finally, we have fixed the local variable referenced before assignment error in the code.

To sum up, as you can see, the UnboundLocalError: local variable referenced before assignment error is raised when you try to assign a value to a local variable before it has been declared. Then, you can solve this error by ensuring that a local variable is declared before you assign it a value. Moreover, if a variable is declared globally that you want to access in a function, you can use the “global” keyword to change its value. In case you have any inquiry, let’s CONTACT US . With a lot of experience in Mobile app development services , we will surely solve it for you instantly.

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UnboundLocalError in line 384 & frozen participant screen

OS: Win 10 Psychopy: v1.5 Error Message: File “D:\separate_components_lastrun.py”, line 384, in run text_L_C = visual.TextStim(win=win, name=‘text_L_C’, UnboundLocalError: local variable ‘visual’ referenced before assignment ################# Experiment ended with exit code 1 [pid:9836] ################# Previous attempts: established the visual.textStim earlier in the code (got a syntax error). Tried to just use builder to make the text boxes and ended up with code talking about the visual.textstim.

I don’t know what to do to get this block of the code to work reliably. I was able to see the participant screen once but was not able to use the keyboard arrows to respond to the prompt. separate_components_lastrun.py (40.9 KB) separate_components.psyexp (104.9 KB)

You have coder code which should be removed for use in Builder. For example, all Builder experiments automatically import a range of libraries.

You shouldn’t therefore import visual, especially not 33 times (end routine within a loop of 3 repetitions of a spreadsheet with 11 conditions).

Also, PsychoPy will already be running in a window called win so when you execute win = visual.Window() you will break the current window. Are you trying to use two windows?

Here is a thread about how to do that

Thank you so much for sending the thread about it. I’ll look into it asap!

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onMessageReceived local variable 'payload' referenced before assignment

I am running version 8.0.15 and on my message handler I am receiving the following message.

I think i solved the issue. It looks like the message handler does not like being sent None for the payload. I changed my code where the message is being sent to send “” if the value is None.

Hmm, so you were specifically calling it as system.perspective.sendMessage("handler", None) ? What happens if you just don’t specify a payload argument in the call?

I have a custom property called jobPath that is bound to the this.props.selection[0] of the tree component.

This custom property jobPath then has a change script on it that send the current value as the payload of the message.

I was not having this issue on 8.0.12

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Python local variable 'message' referenced before assignment problem

I receive the following error:

Error: local variable 'message' referenced before assignment

I think that it must be something related with the alignment of the code but I have double-check it and I can't find any problem. Also, the variable message is only used to return a value.

I have already checked other related questions in this forum and I still cannot find the answer.

I would appreciate your help.

• local-variables

• 1 Think about what happens if none of your conditions are true ... what will be the value of message ? –  juanpa.arrivillaga Commented Jun 16, 2022 at 15:45
• 1 The error you report may not be a runtime error; you appear to be using a static analysis tool that detects the possibility that liquid_filling can be called with some other value for topic , even if at runtime you never do. –  chepner Commented Jun 16, 2022 at 15:48
• 1 But if it is a runtime error, you are mistaken about liquid_filling only being called with the values you are checking for. Look more closely. –  chepner Commented Jun 16, 2022 at 15:49
• 1 @cbcliff47 "They are always true because I use as input an element of a list that contains all the topics that act as conditions in this function." I don't believe you. Provide a minimal reproducible example –  juanpa.arrivillaga Commented Jun 16, 2022 at 15:49
• 1 Even if one of the if statements must be true based on what is passed in (which is not a great way to design a function, but that aside...), your message = i statement will cause a failure because i is never defined. It is also a weakness that liquid_filling is returning an unstable value - sometimes a number, sometimes a string, maybe sometimes None? You should avoid doing that if possible. –  Nathaniel Ford Commented Jun 16, 2022 at 15:53

2 Answers 2

In your case this is happening because for some reason the topic is not passing in your if conditions.

As there is no else , automatically when it does not pass the conditions you will not have message defined, causing it to not find for the return.

Make a new check of the value sent for analysis of conditions or to test that it did not pass any of the conditions, add:

And you will receive this ( not pass conditions ) value as a return, proving that it did not pass the conditions.

In short: you are looking for the problem in the wrong place in your code.

I solved it. It was that I had a topic named "Caps/position" and it should be named "Liquid_filling/position".

The code that works is as follows:

Thanks for your comments because I was able to realize the problem!

• Was that the problem, though, or the thing that revealed the problem? –  Nathaniel Ford Commented Jun 16, 2022 at 15:55
• It was said that as there is no else, when the conditions are not met, the problem is created. So then I realized that I had not well defined the conditions and I will create an else clause to inform when no conditions are met. –  cbcliff47 Commented Jun 16, 2022 at 15:58
• Great! You should probably include that code in your answer - others finding this question won't really see the solution from that description. This is why there is a focus on minimal, reproducible examples - so that the solutions can be made equally clear. –  Nathaniel Ford Commented Jun 16, 2022 at 16:01

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