why it says str not callable?

[nilushika]

>>> li=[4,5]
>>> map(str,li)

Traceback (most recent call last):
  File "<pyshell#1>", line 1, in <module>
    map(str,li)
TypeError: 'str' object is not callable

[bvdet]

You have used 'str' as an identifier which masks the built in type. Delete the identifier.

del str