What are Local and Global Variables in Python?

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In Python, a variable’s scope determines where the variable can be accessed from within a program. The two main scopes for variables are local and global.

What are Local Variables?

Local variables are defined within a function and can only be accessed within that function. They are not accessible outside the function. Once the function execution is completed, the local variables are destroyed. For example, consider the following code:

# This is an example of a local variable
def my_function_local():
    x = 10
    print(x)

my_function_local()

Output:
10

In this code, x is a local variable that is defined within the my_function_local() function. It can only be accessed within that function, and when the function is completed, the variable x is destroyed.

What are Global Variables?

Global variables, on the other hand, are defined outside of any function and can be accessed throughout the program. They can be accessed from within any function or block of code within the program. For example:

x = 20

def my_function_global():
    print(x)

my_function_global()

Output:
20

In this code, x is a global variable that is defined outside of the my_function_global() function. It can be accessed within the function because it is a global variable.

How should Local and global variables be used?

It is generally recommended to limit the use of global variables in your code and use local variables whenever possible, as global variables can make it difficult to debug and maintain code.

As the code gets larger, it can also be harder to pinpoint where a problem has occurred using global variables, as it may be accessed and used in multiple places.

As a result, an analysis of each piece of code referencing the global variable will need to be undertaken. This may lead to project implementation delays and maintenance costs down the line if not managed correctly.