Python difflib module detailed

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The classes and methods provided by the Difflib module are used for the differential comparison of sequences, which can be compared to a file and generate differential results text or HTML-formatted diff pages, and if you need to compare directories, you can use the FILECMP module.

Class Difflib. Sequencematcher

This class provides a way to compare any hash type sequence pair. This method will look for the maximum contiguous sequence of matches that do not contain the ' garbage ' element.

By comparing the complexity of the algorithm, it is due to the original completion matching algorithm, in the worst case there is N squared operation, in the best case, with linear efficiency.

It has an automatic garbage heuristic that allows you to treat characters that repeat more than fragment 1% or repeat 200 times as garbage. You can turn off this feature by setting Autojunk to False.

Class Difflib. Differ

This class compares the differences between lines of text and produces a difference or incremental result that is appropriate for human reading, and the parts of the results are expressed as follows:

Class Difflib. Htmldiff

This class can be used to create an HTML table (or an HTML file that contains a table), with either a display or row-to-row comparison of the results.

Make_file (Fromlines, Tolines [, fromdesc][, todesc][, context][, Numlines])

Make_table (Fromlines, Tolines [, fromdesc][, todesc][, context][, Numlines])

The above two methods can be used to generate an HTML file containing a table with a comparison of the results, and some of the content will be highlighted.

Difflib.context_diff (A, b[, fromfile][, tofile][, fromfiledate][, tofiledate][, n][, Lineterm])

Compares A with B (String list) and returns a generator with a differential text line
Example:

>>> S1 = [' bacon\n ', ' eggs\n ', ' ham\n ', ' guido\n ']>>> s2 = [' python\n ', ' eggy\n ', ' hamster\n ', ' guido\n ' ]>>> in Context_diff (S1, S2, fromfile= ' before.py ', tofile= ' after.py '): ...   Sys.stdout.write (line) * * * before.py---after.py****************** 1,4 ****! bacon! eggs! Ham Guido---1,4----! Python! eggy! Hamster Guido

Difflib.get_close_matches (Word, possibilities[, n][, cutoff])

Returns a list of the maximum matching results

Example:

>>> get_close_matches (' appel ', [' Ape ', ' apple ', ' peach ', ' puppy ']) [' Apple ', ' ape ']>>> import keyword >>> get_close_matches (' wheel ', keyword.kwlist) [' While ']>>> get_close_matches (' Apple ', keyword.kwlist) []>>> get_close_matches (' Accept ', keyword.kwlist) [' except ']

Difflib.ndiff (A, b[, linejunk][, Charjunk])

Compare A with B (String list), return a differ-style difference result
Example:

>>> diff = Ndiff (' one\ntwo\nthree\n '. Splitlines (1),...       ' Ore\ntree\nemu\n '. Splitlines (1)) >>> print '. Join (diff),-one? ^+ ore? ^-Two-three? -+ tree+ EMU

Difflib.restore (sequence, which)

Returns a result of two comparison sequences

Example

>>> diff = Ndiff (' one\ntwo\nthree\n '. Splitlines (1),...       ' Ore\ntree\nemu\n '. Splitlines (1)) >>> diff = list (diff) # materialize the generated delta into a list>>> p Rint ". Join (Restore (diff, 1)),onetwothree>>> print". Join (Restore (diff, 2)), Oretreeemu

Difflib.unified_diff (A, b[, fromfile][, tofile][, fromfiledate][, tofiledate][, n][, Lineterm])

Compare A with B (String list) and return a unified diff format difference result.

Example:

>>> S1 = [' bacon\n ', ' eggs\n ', ' ham\n ', ' guido\n ']>>> s2 = [' python\n ', ' eggy\n ', ' hamster\n ', ' guido\n ' ]>>> in Unified_diff (S1, S2, fromfile= ' before.py ', tofile= ' after.py '): ...  Sys.stdout.write (line)---before.py+++ after.py@@ -1,4 +1,4 @@-bacon-eggs-ham+python+eggy+hamster Guido

Practical Application Examples

Compare two files and then generate an HTML file that shows the difference results

#coding: Utf-8 ' FILE:DIFFLIBEG.PYDATE:2017/9/9 10:33author:lockeyemail:lockey@123.comdesc:diffle module Learning and practising ' import DIFFLIBHD = Difflib. Htmldiff () loads = ' with open (' g:/python/note/day09/0907code/hostinfo/cpu.py ', ' R ') as Load:loads = Load.readlines () Load.close () MEMS = ' with open (' g:/python/note/day09/0907code/hostinfo/mem.py ', ' R ') as Mem:mems = Mem.readlines () Mem.close () with open (' htmlout.html ', ' A + ') as Fo:fo.write (Hd.make_file (Loads,mems)) Fo.close ()

Operation Result:

The resulting HTML file is compared to the result: