UnboundLocalError: Local Variable Referenced Before Assignment
Updated Feb 09, 2023
The “local variable referenced before assignment” error occurs when you give reference of a local variable without assigning any value.
In the above example, we have given the value of variable “v1” in two places.
- Outside the function “myfunction()” .
- And at the end of the function “myfunction()” .
If we assign a value of a variable in the function it becomes local variable to that function, but in the above example we have assigned the value to “v1” variable at the end of the function and we are referring this variable before assigning.
And the variable “v1” which we have assigned at the beginning of the code block is not declared as a global variable.
To avoid an error like “UnboundLocalError: local variable referenced before assignment” to occur, we have to:
- Declare GLOBAL variable
- Pass parameters with the function
Declare Global Variable
Code example with global variable:
As we know if we declare any variable as global then its scope becomes global.
Pass function with Parameters
Code example passing parameters with function:
In the above example, as you can see, we are not using a global variable but passing the value of variable “v1” as a parameter with the function “myfunction()”.
In the "example2 ", we have called a function “dayweek()” with parameter value “10” which gives the error but the same function with value “1” which runs properly in “example 2.1” and returns the output as “Weekday”.
Because in the above function we are assigning the value to variable “wd” if the value of variable " day " is the range from (0 to 7) . If the value of variable " day " greater than "7" or lower then " 0" we are not assigning any value to variable " wd " That's why, whenever the parameter is greater than 7 or less than 0, python compiler throws the error “ UnboundLocalError: local variable 'wd' referenced before assignment ”
To avoid such type of error you need assign the function variable which lies within the range or we need to assign some value like " Invalid Value " to variable " wd " if the value of variable " day " is not in range from ( 0 to 7 )
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Local variable referenced before assignment in Python
Last updated: Feb 17, 2023 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.
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
Copyright © 2023 Borislav Hadzhiev
Local variable referenced before assignment in Python
The “local variable referenced before assignment” error occurs in Python when you try to use a local variable before it has been assigned a value.
This error typically arises in situations where you declare a variable within a function but then try to access or modify it before actually assigning a value to it.
Here’s an example to illustrate this error:
In this example, you would encounter the “local variable ‘x’ referenced before assignment” error because you’re trying to print the value of x before it has been assigned a value. To fix this, you should assign a value to x before attempting to access it:
In the corrected version, the local variable x is assigned a value before it’s used, preventing the error.
Keep in mind that Python treats variables inside functions as local unless explicitly stated otherwise using the global keyword (for global variables) or the nonlocal keyword (for variables in nested functions).
If you encounter this error and you’re sure that the variable should have been assigned a value before its use, double-check your code for any logical errors or typos that might be causing the variable to not be assigned properly.
Using the global keyword
If you have a global variable named letter and you try to modify it inside a function without declaring it as global, you will get error.
This is because Python assumes that any variable that is assigned a value inside a function is a local variable, unless you explicitly tell it otherwise.
To fix this error, you can use the global keyword to indicate that you want to use the global variable:
Using nonlocal keyword
The nonlocal keyword is used to work with variables inside nested functions, where the variable should not belong to the inner function. It allows you to modify the value of a non-local variable in the outer scope.
For example, if you have a function outer that defines a variable x , and another function inner inside outer that tries to change the value of x , you need to use the nonlocal keyword to tell Python that you are referring to the x defined in outer , not a new local variable in inner .
Here is an example of how to use the nonlocal keyword:
If you don’t use the nonlocal keyword, Python will create a new local variable x in inner , and the value of x in outer will not be changed:
How to Fix Local Variable Referenced Before Assignment Error in Python
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.
Fixing local variable referenced before assignment error
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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[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:
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.
Trending Python Articles
How to fix UnboundLocalError: local variable 'x' referenced before assignment in Python
by Nathan Sebhastian
Posted on May 26, 2023
Reading time: 2 minutes
One error you might encounter when running Python code is:
This error commonly occurs when you reference a variable inside a function without first assigning it a value.
You could also see this error when you forget to pass the variable as an argument to your function.
Let me show you an example that causes this error and how I fix it in practice.
How to reproduce this error
Suppose you have a variable called name declared in your Python code as follows:
Next, you created a function that uses the name variable as shown below:
When you execute the code above, you’ll get this error:
This error occurs because you both assign and reference a variable called name inside the function.
Python thinks you’re trying to assign the local variable name to name , which is not the case here because the original name variable we declared is a global variable.
How to fix this error
To resolve this error, you can change the variable’s name inside the function to something else. For example, name_with_title should work:
As an alternative, you can specify a name parameter in the greet() function to indicate that you require a variable to be passed to the function.
When calling the function, you need to pass a variable as follows:
This code allows Python to know that you intend to use the name variable which is passed as an argument to the function as part of the newly declared name variable.
Still, I would say that you need to use a different name when declaring a variable inside the function. Using the same name might confuse you in the future.
Here’s the best solution to the error:
Now it’s clear that we’re using the name variable given to the function as part of the value assigned to name_with_title . Way to go!
The UnboundLocalError: local variable 'x' referenced before assignment occurs when you reference a variable inside a function before declaring that variable.
To resolve this error, you need to use a different variable name when referencing the existing variable, or you can also specify a parameter for the function.
I hope this tutorial is useful. See you in other tutorials.
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