Understanding Global Variables and the global Keyword in Python

I haven't used Python for a while and realized I've forgotten many of the syntax rules I previously learned; the lack of systematic practice made it hard to recall them fluently.

To achieve flexible use of Python, one should not only be able to write code but also integrate learning, doing, and teaching—learning through doing, teaching while doing, and teaching to reinforce learning.

Scope of Global Variables:

Variables defined outside a function are global, while those defined inside a function are local. Global variables are accessible in all scopes, whereas local variables are only usable within their defining function. When a name exists in both scopes, the local variable takes precedence.

global keyword:

To solve the problem of using global variables inside functions, Python provides the global keyword, which can be used to explicitly declare a variable as global.

The effect of the global keyword is to declare that a variable (e.g., var ) is global.

Example 1: Assignment inside a function cannot change a global variable's value

Result:

It can be seen that assigning a value inside the function does not change the global variable, so the global keyword is needed.

Example 2: Changing a global variable's value requires the global keyword

Test result:

The demonstration shows that a global variable's value can only be changed when the global keyword is used; otherwise the assignment creates a new local variable. This point should be remembered.

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