python when local variable uses a build-in function name

Question

I have the following simple python script, test_type.py

#!/usr/bin/env python

for type, path in [('dir', 'c:/users')]:
    print(f'{type}={path}')

mystring = 'this string'

if type(mystring) == str:
    print(mystring)

when I run it, I got error

dir=c:/users
Traceback (most recent call last):
  File "test_type.py", line 8, in <module>
    if type(mystring) == str:
TypeError: 'str' object is not callable

The error is likely due to using 'type' as both a local variable and a build-in function name, because when I comment out the for loop, the error is gone.

But why is this a problem? The first 'type' is a local variable; it shouldn't pollute the namespace.

Background:

• The test script is extracted from a big program I am working on.

• I tested the script in both python 3.8.5 on ubuntu and 3.10.2 on windows 10. Both behaves the same.

• I can change my program to use a different variable name but I'd like to know the reason because I could inadvertently bump into similar problem again. It took me a while to narrow it down.

Thank you