How come empty value is matching with array value in python

Question

I am matching an empty value with an array element which has one value in it and the array does not have any empty values. However, still this script works.

import re

b = ""
links_check_arr = ['Arunsdsdds']
for links_find in links_check_arr:
    if b in links_find:
        print  links_find
        print b

How come it is working when b is empty and the array element is 'Arunsdsdds' (which has no empty value in it)?

An empty string is contained in every non-empty string (and obviously in any other empty string). Use `==` instead of `in`. — DeepSpace, Jul 05 '16 at 06:59
Possible duplicate of [Why Python returns True when checking if an empty string is in another?](http://stackoverflow.com/questions/27603885/why-python-returns-true-when-checking-if-an-empty-string-is-in-another) — tripleee, Jul 26 '16 at 06:22

score 2 · Answer 1 · answered Jul 05 '16 at 06:59

2

An empty string is always considered to be part of any string:

>>> "" in "abcd"
True

answered Jul 05 '16 at 06:59

sidney

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score 1 · Answer 2 · answered Jul 05 '16 at 06:59

The empty string is a substring of every string in Python. This is because the substring of length 0 of any string s[0:0] is equal to the empty string.

A proper way to check if a string s is not empty is simply if not s:, as empty strings are "falsey".

To check if something is equal to the empty string, just use == as opposed to in.

score 0 · Answer 3 · edited May 23 '17 at 11:51

tristan gives a detailed answer in the post Why Python returns True when checking if an empty string is in another?. The important sentence is there:

Empty strings are always considered to be a substring of any other string, so "" in "abc" will return True.

You find this sentence in the Python 2.7. reference, article Expressions in the chapter Comparisons. Or for Python 3 in Expressions, chapter Membership test operations.

How come empty value is matching with array value in python

3 Answers3