Python DiffLib

difflib is a module for producing file deltas.

Usage

Consider an 'old' file like:

foo
bar


baz
1
2
3

And a 'new' file like:

foo
bar
baz
1
5
3

Context Diff

Use context_diff to create a delta in context diff format.

To create a file like:

*** a.txt
--- b.txt
***************
*** 1,9 ****
  foo
  bar
- 
- 
  baz
  1
! 2
  3
  
--- 1,7 ----
  foo
  bar
  baz
  1
! 5
  3

Try:

import difflib

with open('a.txt', 'r') as f:
    old = f.readlines()
with open('b.txt', 'r') as f:
    new = f.readlines()

d = difflib.context_diff(old, new, fromdesc='a.txt', todesc='b.txt')

with open('diff.txt', "w") as f:
    f.writelines(d)

Differ

Use ndiff to create a delta in differ style.

Try create a file like:

  foo
  bar
- 
- 
  baz
  1
- 2
+ 5
  3

Try:

import difflib

with open('a.txt', 'r') as f:
    old = f.readlines()
with open('b.txt', 'r') as f:
    new = f.readlines()

d = difflib.ndiff(old, new)

with open('diff.txt', "w") as f:
    f.writelines(d)

Unified Diff

Use unified_diff to create a delta in unified diff format.

To create a file like:

--- a.txt
+++ b.txt
@@ -1,9 +1,7 @@
 foo
 bar
-
-
 baz
 1
-2
+5
 3

Try:

import difflib

with open('a.txt', 'r') as f:
    old = f.readlines()
with open('b.txt', 'r') as f:
    new = f.readlines()

d = difflib.unified_diff(old, new, fromdesc='a.txt', todesc='b.txt')

with open('diff.txt', "w") as f:
    f.writelines(d)

HTML Table

To create a stylized HTML table with line-by-line comparisons, use the HtmlDiff class.

import difflib

with open('a.txt', 'r') as f:
    old = f.readlines()
with open('b.txt', 'r') as f:
    new = f.readlines()

d = difflib.HtmlDiff(wrapcolumn=80).make_file(old, new, fromdesc='a.txt', todesc='b.txt')

with open('diff.html', "w") as f:
    f.write(d)

Functions

Diff_Bytes

Get_Close_Matches

Is_Character_Junk

Is_Line_Junk

Restore

Classes

Differ

SequenceMatcher

See also

Python difflib module documentation

Python Module of the Day article for difflib

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