Python Diff Two Multiline Strings Like GitHub

Question

I want to achieve a diff output like github's commit diff view. And I tried this:

import difflib

first = """
def
baz
"""

second = """
deff
ba
bar
foo
"""

diff = ''
for text in difflib.unified_diff(first, second):
    for prefix in ('---', '+++', '@@'):
        if text.startswith(prefix):
            break
    else:
        diff += text

The output is:

 d e f+f 
 b a-z 
+b+a+r+
+f+o+o+

How can I achieve,

1 def+f
2 ba-z
+
3 bar
4 foo
# -
# 5 line
# 6 line

an output just like this. Thanks.

I'm not quite sure how you are initialising the first and second variables. Could you update your example to show the exact code you are running? — Jon Betts, Jun 03 '17 at 20:45

score 9 · Accepted Answer · answered Jun 05 '17 at 16:12

I'm not quite sure what format you mean with gitlab; I've not seen char-by-char diffs in gitlab like your example. If you want a more standardish line-by-line output, then I think you just have to pass lists to the diff function:

for text in difflib.unified_diff(first.split("\n"), second.split("\n")):
    if text[:3] not in ('+++', '---', '@@ '):
        print text

As every line is different in your example, diff is just going to see each line as having been totally changed and give you an output like:

-def
-baz
+deff
+ba
+bar
+foo

If you want to do something more fancy, you can treat the data as a single string (as you were) and then try and split on new-lines. The return format seems to be "{operation}{char}" (including new line chars), so you can group and detect lines which all have the same operation and apply the correct logic.

I can't quite work out the rules you're trying to apply based on your example (are you grouping all mixed lines, then added lines then removed lines or something else?), so I can't give you an exact example.

Python Diff Two Multiline Strings Like GitHub

1 Answers1