Python how to check if a string contains a word

Question

i am trying to check if str1 exist in str2

def string_contains(str1,str2):
    return bool (str1 in str2)

print (string_contains("llo","hello how are you"))
# expected false but return value is true
# the possible true for s1 is hello or hello how or hello how are
# hello how are you

Have you done any research about how `in` works with strings? Any at all? — TigerhawkT3, Jan 20 '16 at 01:01
@J.J.Hakala - Read this question more carefully. It's not a duplicate. — TigerhawkT3, Jan 20 '16 at 01:12
...but `"llo"` is in str2. Its the last 3 letters in `"hello"`. Can you be more speicific in your requirements? The example hints that the match must be at the start of str2 and must match on word boundaries... correct? — tdelaney, Jan 20 '16 at 01:18
What about "how are you" or "you"? Should they also return `True`? — mhawke, Jan 20 '16 at 01:19
From your description, `str2.startswith(str1)` is sufficient. But it would match "Hello how ar" for instance. — tdelaney, Jan 20 '16 at 01:27

score 1 · Answer 1 · answered Jan 20 '16 at 01:32

This should work - it will ensure only whole words are matched, and sentences must match from the start.

def string_contains(str1,str2):
    lst1 = str1.split(' ')
    lst2 = str2.split(' ')

    if len(lst1) <= len(lst2):
        return lst1 == lst2[:len(lst1)]

    return False

print (string_contains("llo", "hello how are you"))  # False
print (string_contains("hello", "hello how are you"))  # True
print (string_contains("hello how", "hello how are you"))  # True
print (string_contains("hello how a", "hello how are you"))  # False

You can use a `first_idx = lst2.index(lst1[0])` to get answers that don't match from the start. It can raise an exception that needs to be treated if there's no match between the list. — pekapa, Jan 20 '16 at 02:15

score 0 · Answer 2 · answered Jan 20 '16 at 03:15

0

I like using regular expression module re.

Code:

import re

pattern = re.compile('\sllo\s')  # add another parameter `re.I` for case insensitive
match = pattern.search('hello how are you')
if match:
    return True
else:
    return False

answered Jan 20 '16 at 03:15

tanglong

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Python how to check if a string contains a word

2 Answers2