[SOLVED] Local Variable Referenced Before Assignment

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

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Local Variable Referenced Before Assignment Error with Explanation

Try these examples yourself using our Online Compiler.

Let’s look at the following function:

Local Variable Referenced Before Assignment Error

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.

FAQs on Local Variable Referenced Before Assignment

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.

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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How to Fix Local Variable Referenced Before Assignment Error in Python

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Local Variable referenced before assignment

I was wondering if you guys could help. I'm trying to do a simple view where it sends the user to the client creation form, but I keep getting this error:

local variable 'form' referenced before assignment

Looking at my code, I can't see whats wrong.

Anyone tell me where I went wrong?

Jean-François Corbett's user avatar

2 Answers 2

This is what is happening:

As to how to fix it, that's really for you to decide. What the fix is depends on what you want your code to do in case the request method is not POST .

David Heffernan's user avatar

You almost certainly want to de-indent this part:

That is, on the initial GET of the page, use a blank client form, then when the page is POSTed, use the request POST data to fill in the form object.

Russell Borogove's user avatar

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Local variable referenced before assignment: The UnboundLocalError in Python

When you start introducing functions into your code, you’re bound to encounter an UnboundLocalError at some point. Because you try to use a local variable referenced before assignment. So, in this guide, we talk about what this error means and why it is raised. We walk through an example in action to help you understand how you can solve it.

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Local variable referenced before assignment

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: local variable 'request' referenced before assignment #492

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Igor-davidyuk commented aug 30, 2022 • edited.

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Local variable referenced before assignment in Python

In Python, while working with functions, you can encounter various types of errors. A common error when working with the functions is “ Local variable referenced before assignment ”. The stated error occurs when a local variable is referenced before being assigned any value.

This write-up will provide the possible reasons and the appropriate solutions to the error “Local variable referenced before assignment” with practical examples. The following aspects are discussed in this write-up in detail:

Reason: Reference a Local Variable

Solution 1: mark the variable globally, solution 2: using function parameter value, solution 3: using nonlocal keyword.

The main reason for the “ local variable referenced before assignment ” error in Python is using a variable that does not have local scope. This also means referencing a local variable without assigning it a value in a function.

The variable initialized inside the function will only be accessed inside the function, and these variables are known as local variables. To use variables in the entire program, variables must be initialized globally. The below example illustrates how the “ UnboundLocalError ” occurs in Python.

local variable referenced before assignment

In the above snippet, the “ Student ” variable is not marked as global, so when it is accessed inside the function, the Python interpreter returns an error.

Note: We can access the outer variable inside the function, but when the new value is assigned to a variable, the “UnboundLocalError” appears on the screen.

To solve this error, we must mark the “ Student ” variable as a global variable using the keyword “ global ” inside the function.

In the above code, the local variable is marked as a “ global ” variable inside the function. We can easily reference the variable before assigning the variable in the program.

local variable referenced before assignment

The above snippet proves that the global keyword resolves the “unboundLocalError”.

Passing a value as an argument to the function will also resolve the stated error. The function accepts the variable as an argument and uses the argument value inside the function. Let’s have a look at the given below code block for a better understanding:

In the above code, the variable is referenced before assigning the value inside the user-defined function. The program executes successfully without any errors because the variable is passed as a parameter value of the function.

local variable referenced before assignment

The above output shows the value of the function when the function is accessed in the program without any “ Local Variable referenced ” error.

The “ nonlocal ” keyword is utilized in the program to assign a new value to a local variable of function in the nested function. Here is an example of code:

In the above code, the keyword “ nonlocal ” is used to mark the local variable of the outer function as nonlocal. After making the variable nonlocal, we can reference it before assigning a value without any error.

local variable referenced before assignment

The above output shows the value of the inner function without any “ local variable referenced ” error in a program.

The “ Local variable referenced before assignment ” appears in Python due to assigning a value to a variable that does not have a local scope. To fix this error, the global keyword, return statement, and nonlocal nested function is used in Python script. The global keywords are used with variables to make it able to access inside and outside the function. The return statement is also used to return the variable’s new value back to function and display the result on the screen. This Python guide presented a detailed overview of the reason and solutions for the error “Local variable referenced before assignment” in Python.

Joseph

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COMMENTS

  1. Python 3: UnboundLocalError: local variable referenced before assignment

    If you set the value of a variable inside the function, python understands it as creating a local variable with that name. This local variable masks the global variable. In your case, Var1 is considered as a local variable, and it's used before being set, thus the error.

  2. python

    UnboundLocalError: local variable 'total' referenced before assignment. At the start of the file (before the function where the error comes from), I declare total using the global keyword. Then, in the body of the program, before the function that uses total is called, I assign it to 0.

  3. [SOLVED] Local Variable Referenced Before Assignment

    Local Variables can only be accessed within their own function. All functions of the program can access global variables. Local variables are immune to changes in the global scope. Thereby being more secure. Global Variables are less safer from manipulation as they are accessible in the global scope.

  4. Python local variable referenced before assignment Solution

    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.

  5. How to Fix Local Variable Referenced Before Assignment Error …

    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 …

  6. python

    Local Variable referenced before assignment. I was wondering if you guys could help. I'm trying to do a simple view where it sends the user to the client creation form, but I keep getting this error: Looking at my code, I can't see whats wrong. def add_client (request): user = request.user if request.method =='POST': form = AddClientForm ...

  7. Local variable referenced before assignment: The …

    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.

  8. UnboundLocalError: local variable 'request' referenced before ...

    For my experiments on CIFAR-10, until now I have used ResNet-18 or an EfficientNet. In the jupyter notebook, I initialise these models in this way: resnet18 = torchvision.models.resnet18(pretrained...

  9. Local variable referenced before assignment in Python

    Solution 1: Mark the Variable globally Solution 2: Using Function Parameter Value Solution 3: Using nonlocal Keyword Reason: Reference a Local Variable The main reason for the “ local variable referenced before assignment ” error in Python is using a variable that does not have local scope.

  10. UnboundLocalError: local variable referenced before assignment

    The UnboundLocalError: local variable referenced before assignment occurs when you reference a local variable before assigning any value to it inside a function. The UnboundLocalError can be resolved by changing the variable's scope to global using the global keyword inside the function definition. How to Reproduce the Error