How to search for a word (exact match) within a string?

I am trying to substring search

>>>str1 = 'this'
>>>str2 = 'researching this'
>>>str3 = 'researching this '

>>>"[^a-z]"+str1+"[^a-z]" in str2
False

>>>"[^a-z]"+str1+"[^a-z]" in str3
False

I wanted to True when looking in str3开发者_如何学C. what am I doing wrong?

You want Python's re module:

>>> import re
>>> regex = re.compile(r"\sthis\s") # \s is whitespace
>>> # OR
>>> regex = re.compile(r"\Wthis\W")
>>> # \w is a word character ([a-zA-Z0-9_]), \W is anything but a word character
>>> str2 = 'researching this'
>>> str3 = 'researching this '
>>> bool(regex.search(str2))
False
>>> regex.search(str3)
<_sre.SRE_Match object at 0x10044e8b8>
>>> bool(regex.search(str3))
True

I have a hunch you're actually looking for the word "this", not "this" with non-word characters around it. In that case, you should be using the word boundary escape sequence \b.

It looks like you want to use regular expressions, but you are using ordinary string methods. You need to use the methods in the re module:

import re
>>> re.search("[^a-z]"+str1+"[^a-z]", str2)
>>> re.search("[^a-z]"+str1+"[^a-z]", str3)
<_sre.SRE_Match object at 0x0000000006C69370>

For regular expressions in Python, use the re module:

>>> import re
>>> re.search("[^a-z]"+str1+"[^a-z]", str2) is not None
False
>>> re.search("[^a-z]"+str1+"[^a-z]", str3) is not None
True

import re
str1 = 'this'
str2 = 'researching this'
str3 = 'researching this '

if re.search("[^a-z]"+str1+"[^a-z]", str2):
    print "found!"

if re.search("[^a-z]"+str1+"[^a-z]", str3):
    print "found!"

I don't think in does a regex search.

Take a look at the re module.

It's unclear what you're actually trying to do, but if you want to know if "this" is in "researching this", do:

"this" in "researching this"

(or)

str1 in str3

Or if you're trying to find it as an entire word only, do:

"this" in "researching this".split()

The result is that it will split "researching this" into ["researching", "this"] and then check for the exact word "this" in it. So, this is False:

"this" in "researching thistles".split()

use re module. re module is the one that you should use. re rocks.