difference between two strings in python/php

Question

I'm looking for an easy way to compare two similar strings and output the difference for instance if I have

"abcdefghijklmnop" and "abcdefghi"

the function would output

"jklmnop"

I need to know how to do this in both php and python

Answer 1

In PHP. array_diff compares the first against the second array and returns the difference.

$a1 = str_split('abcdefghijklmnop');
$a2 = str_split('abcdefghi');

echo join('', array_diff($a1, $a2)); // jklmnop

This will work as well.

$s1 = 'abcdefghijklmnop';
$s2 = 'abcdefghi';

echo str_replace(str_split($s2), '', $s1); // jklmnop

This could handle $s2 = 'ghiabcdef'; as well because str_replace() is fed with an array, not a string.

Answer 2

In Python, you can do:

x = "abcdefghijklmnop"
y = x.replace("abcdefghi", "")

# y now equals "jklmnop"

Answer 3

>>> s1 = "abcdefghijklmnop"
>>> s2 = "abcdefghi"
>>> s1.strip(s2)
'jklmnop'

Answer 4

Python has the difflib module in its standard library that can be used to do this.

import difflib

s1 = "abcdefghijklmnop"
s2 = "abcdefghi"
s = difflib.SequenceMatcher(s1, s2)
for block in s.get_matching_blocks():
    print "match of length %d at a[%d] and b[%d]" % block

difflib is very powerful and has many different ways of searching for differences. Some study of the documentation would be worthwhile if you choose to use this.

Answer 5

In Python:

>>> s1 = 'abcdefghijklmnop'
>>> s2 = 'abcdefghi'
>>> set(s1) - set(s2)
set(['k', 'j', 'm', 'l', 'o', 'n', 'p'])

Answer 6

In Python:

string1 = "abcdefghijklmnop"
string2 = "abcdefghi"

def stringComp(string1, string2):
   if len(string1.split(string2)) > 0:
    if string1 == string1.split(string2)[0]:
     finalstring = stringComp(string2, string1)
    else:
     finalstring = ''.join(string1.split(string2))
   else:
      finalstring = ""
   return finalstring

This should always give you the difference in the strings. However, I'm sure there is a much easier way to do this.