Confused by list behavior of python [duplicate]

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• How to modify list entries during for loop? 5 answers

Iam a novice in Python .Python list cannot be amended in a loop . The output for this is unchanged array str1. Iam trying to make this list zero.This is a little strange for me . Why cant I change the elements of the list ?

 import re,string
 str1=["This is a review","This is not a review"]
 for each in str1:
    each=" "
 print str1

Any clue?