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:
local variable referenced before assignment
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:
value = 1 def increment(): value = value + 1 print(value) increment()
If you run this code, you'll get
UnboundLocalError: local variable 'value' referenced before assignment
The issue is that in this line:
value = value + 1
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 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:
value = 1 def increment(): global value value = value + 1 print(value) increment()
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!
Leave us a message!