python compare subsection of 2 strings and see if they match

Question

I have 2 strings e.g.

str1 = 'section1.1:  this is a heading for section 1'

and

str2 = 'section1.1:  this is a heading for section 1.1'

I want to compare the text which comes after 'section1.1:' and return whether it is the same or not. In the example it would return false as the first says section 1 and the second says section 1.1

The first piece of the string can be anything e.g. subsection2.5: but always ends with a :

What is the best way to do this using Python?

Answer 1

Use the split method of the strings to split on only the first ::

>>> str1 = 'section1.1:  this is a heading for section 1'
>>> str2 = 'section1.1:  this is a heading for section 1.1'
>>> str1.split(':', 1)[1]
'  this is a heading for section 1'
>>> str2.split(':', 1)[1]
'  this is a heading for section 1.1'

Answer 2

Depending on how well you know what the format will be, you might do something like this.

In [1]: str1 = 'section1.1:  this is a heading for section 1'
In [2]: str2 = 'section1.1:  this is a heading for section 1.1'
In [3]: if str1.split(":", 1)[1] == str2.split(":", 1)[1]: 
   ...:     print "true"


In [4]: str2 = 'section1.1:  this is a heading for section 1'

In [7]: if str1.split(":", 1)[1] == str2.split(":", 1)[1]:
   ...:     print "true"


   true

You can always strip the responses if you're concerned about trailing or leading whitespace to be different.

(edit: Missing line in IPython session)

Answer 3

You can translate this pretty directly into code:

def compare( str1, str2):
   # I want to compare the text which comes after the first ':' (for example)
   def find_that_part( s ):
       idx = s.find(':') # where is the first ':'?
       return s[idx:] # the part after it

   # and return whether it is the same or not.
   return find_that_part(str1) == find_that_part(str2)

Answer 4

The split(":") solutions in the other answers work fine. If you already parsed the first part (before the colon) in some way, and you know the length, you could do a simple string comparison like this:

parsedUntilColon = "section1.1:" # for example

if str1[len(parsedUntilColon):] == str2[len(parsedUntilColon):]:
    print "strings are equal"

Answer 5

A one liner should be cool!!

>>> str1 = 'section1.1:  this is a heading for section 1'
>>> str2 = 'section1.1:  this is a heading for section 1.1'
>>> cmp = lambda str1, str2: [x_.findall(str1) == x_.findall(str2) for x_ in [re.compile(':[\w*\s*\.*]*')]][0] and True
>>> cmp(str1, str2)
False