Developers often encounter the UnboundLocalError Local Variable Referenced Before Assignment error in Python. In this article, we will see what is local variable referenced before assignment error in Python and how to fix it by using different approaches.
This error 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.
Syntax:
UnboundLocalError: local variable 'x' referenced before assignment
Below, are the reasons by which UnboundLocalError: Local variable Referenced Before Assignment error occurs in Python :
In this code, the outer_function defines a variable ‘x’ and a nested inner_function attempts to access it, but encounters an UnboundLocalError due to a local ‘x’ being defined later in the inner_function.
Hangup (SIGHUP) Traceback (most recent call last): File "Solution.py", line 12, in outer_function() File "Solution.py", line 10, in outer_function inner_function() File "Solution.py", line 5, in inner_function print(x) # Trying to access 'x' from the outer function UnboundLocalError: local variable 'x' referenced before assignment
In this code, the function example_function tries to increment the global variable ‘x’, but encounters an UnboundLocalError since it’s treated as a local variable due to the assignment operation within the function.
Hangup (SIGHUP) Traceback (most recent call last): File "Solution.py", line 7, in example_function() File "Solution.py", line 4, in example_function x += 1 # Trying to modify global variable 'x' without declaring it as global UnboundLocalError: local variable 'x' referenced before assignment
Below, are the approaches to solve “Local variable Referenced Before Assignment”.
In this code, example_function successfully modifies the global variable ‘x’ by declaring it as global within the function, incrementing its value by 1, and then printing the updated value.
In this code, the outer_function defines a local variable ‘x’, and the inner_function accesses and modifies it as a nonlocal variable, allowing changes to the outer function’s scope from within the inner function.