Can Python Functions Access Global Variables Without the `global` Keyword?

Can We Access Global Variables Without 'global' Keyword? A Python Conundrum

In Python, the 'global' keyword typically allows functions to access and modify variables defined outside their local scope. However, it seems paradoxical that accessing a global variable from within a function can be achieved without explicitly using 'global'.

Let's consider the following example:

sub = ['0', '0', '0', '0']

def getJoin():
    return '.'.join(sub)

print(getJoin())

In this code, 'sub' is a global variable, and the function 'getJoin()' accesses it without using the 'global' keyword. This may raise questions about the purpose of 'global' if its use is apparently dispensable.

To understand why this occurs, we need to delve into Python's scoping rules. In Python, every function creates a separate namespace for local variables. However, global variables are accessible from any scope within the program.

In the absence of the 'global' keyword, when a function references a variable that doesn't exist in its local namespace, Python searches for it in the global namespace. If found, the function can access and modify the global variable. This is known as implicit global lookup.

In the example, 'sub' is a global variable that 'getJoin()' implicitly accesses. Since 'sub' is defined outside 'getJoin()' and is not shadowed by a local variable within the function, it can be accessed directly.

However, it's important to note that modifying global variables from within functions without using 'global' is generally discouraged as it can lead to unintentional side effects and code confusion. The 'global' keyword explicitly declares that a variable is global, making it clear to the reader and the interpreter that the variable is not local to the function.

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