local variable referenced before assignment

This error occurs when a local variable is referenced before it has been assigned a value. In Python, all variables must be assigned a value before they can be used.

For example, consider the following code:

def foo():
    print(x)
    x = 10

foo()

This will result in a "local variable 'x' referenced before assignment" error because we are trying to print the value of `x` before we have assigned it a value.

To fix this error, we need to assign a value to `x` before we try to use it:

def foo():
    x = 10
    print(x)

foo()

Now the code will run without any errors.