Why Does Redefining `str` Cause a `TypeError` in Subsequent Python Function Calls?

Redefining str Causes TypeError in Second Execution

The provided Python code exhibits peculiar behavior, where the call to example(1) executes without issue, but example(2) triggers a TypeError. This puzzling phenomenon stems from the problematic code sequence:

global str
str = str(parameter)

Within this block, the code assigns the value str(parameter) to the global str variable. This redefinition essentially overrides the built-in Python name of the string type, causing conflicts with subsequent operations.

The Problem

The built-in str() function is used to convert objects into strings. By redefining str with str(parameter), the code effectively replaces the original function with a custom variable holding the converted value of parameter.

As a result, in the second call to example(2), when the code attempts to use str again, it's no longer a function but instead a string object. Consequently, the interpreter raises a TypeError because string objects cannot be called like functions.

The Solution

To rectify this issue, refrain from modifying the built-in str name. Instead, assign a different name to the local variable that stores the converted value. Additionally, remove the global statement, which is unnecessary since the local variable is not modifying any existing global variable.

Here's the corrected code:

def example(parameter):
    s = str(parameter)  # Use a different name for the local variable
    print(s)  # Use the newly created local variable

example(1)
example(2)

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