How Can I Modify a Global Variable Within a Python Function?

Modifying Global Variables in Python Functions

Background

While using global variables is generally discouraged in Python, let's explore the approach suggested in the question:

x = "somevalue"

def func_A():
    # Access and modify the global variable x
    # Required to use the 'global' keyword
    global x
    x = "modified"
    
def func_B():
    # Call func_A and store the modified global variable x
    x = func_A()

Using the global Keyword

The key point is to use the global keyword within the function that intends to modify the global variable. This explicitly tells Python to refer to the global scope rather than creating a local variable with the same name.

global x
x = "modified"

In this case, the global x statement within func_A allows it to modify the global variable x, which is then reflected in func_B.

Order of Function Calls

In Python, the order of function definitions does not matter, as they are loaded into the execution environment before runtime. However, the order of function calls does matter. In the given example, func_A must be called before func_B, as func_B relies on x being modified by func_A.

Conclusion

Using the global keyword is necessary to modify global variables within functions. The order of function calls is important to ensure that the desired modifications are made before using the variable in other functions.

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