Python - difference between two strings

Question

I'd like to store a lot of words in a list. Many of these words are very similar. For example I have word afrykanerskojęzyczny and many of words like afrykanerskojęzycznym, afrykanerskojęzyczni, nieafrykanerskojęzyczni. What is the effective (fast and giving small diff size) solution to find difference between two strings and restore second string from the first one and diff?

Answer 1

You can use ndiff in the difflib module to do this. It has all the information necessary to convert one string into another string.

A simple example:

import difflib  cases=[('afrykanerskojęzyczny', 'afrykanerskojęzycznym'),        ('afrykanerskojęzyczni', 'nieafrykanerskojęzyczni'),        ('afrykanerskojęzycznym', 'afrykanerskojęzyczny'),        ('nieafrykanerskojęzyczni', 'afrykanerskojęzyczni'),        ('nieafrynerskojęzyczni', 'afrykanerskojzyczni'),        ('abcdefg','xac')]   for a,b in cases:          print('{} => {}'.format(a,b))       for i,s in enumerate(difflib.ndiff(a, b)):         if s[0]==' ': continue         elif s[0]=='-':             print(u'Delete "{}" from position {}'.format(s[-1],i))         elif s[0]=='+':             print(u'Add "{}" to position {}'.format(s[-1],i))         print()       

prints:

afrykanerskojęzyczny => afrykanerskojęzycznym Add "m" to position 20  afrykanerskojęzyczni => nieafrykanerskojęzyczni Add "n" to position 0 Add "i" to position 1 Add "e" to position 2  afrykanerskojęzycznym => afrykanerskojęzyczny Delete "m" from position 20  nieafrykanerskojęzyczni => afrykanerskojęzyczni Delete "n" from position 0 Delete "i" from position 1 Delete "e" from position 2  nieafrynerskojęzyczni => afrykanerskojzyczni Delete "n" from position 0 Delete "i" from position 1 Delete "e" from position 2 Add "k" to position 7 Add "a" to position 8 Delete "ę" from position 16  abcdefg => xac Add "x" to position 0 Delete "b" from position 2 Delete "d" from position 4 Delete "e" from position 5 Delete "f" from position 6 Delete "g" from position 7 

Answer 2

I like the ndiff answer, but if you want to spit it all into a list of only the changes, you could do something like:

import difflib  case_a = 'afrykbnerskojęzyczny' case_b = 'afrykanerskojęzycznym'  output_list = [li for li in difflib.ndiff(case_a, case_b) if li[0] != ' ']