Getting more info from filecmp

[starlite79]

Hello,

I am using the cmp function of the module filecmp interactively as follows:

import filecmp
filecmp.cmp('file1', 'file2')

If they're the same, the result is true, otherwise false.

If the files are not the same, is there a way to get line numbers where the files differ or something with more information than just False?

 

[JustinEzequiel]

yes. see the difflib module

 

[starlite79]

Justin,

I looked at the difflib module and found a function called ndiff. I tried to use it as follows:

>>> import difflib
>>> difflib.ndiff('test.case', 'tidesmod.test')
<generator object at 0x2ab44efaa878>

What does that mean? In the example I used, the files are the same. Could someone give an example of how to use the difflib module for file comparison? I don't want to match keywords or patterns in files.

 

[JustinEzequiel]

difflib works on lists of strings so you'll have to read in the lines yourself

also try
>>> help(difflib) and
>>> help(deifflib.ndiff)
in your interactive prompt

ndiff(a, b, linejunk=None, charjunk=<function IS_CHARACTER_JUNK>)
Compare `a` and `b` (lists of strings); return a `Differ`-style delta.

Optional keyword parameters `linejunk` and `charjunk` are for filter
functions (or None):

- linejunk: A function that should accept a single string argument, and
return true iff the string is junk. The default is None, and is
recommended; as of Python 2.3, an adaptive notion of "noise" lines is
used that does a good job on its own.

- charjunk: A function that should accept a string of length 1. The
default is module-level function IS_CHARACTER_JUNK, which filters out
whitespace characters (a blank or tab; note: bad idea to include newline
in this!).

Tools/scripts/ndiff.py is a command-line front-end to this function.

Example:

>>> diff = ndiff('one\ntwo\nthree\n'.splitlines(1),
... 'ore\ntree\nemu\n'.splitlines(1))
>>> print ''.join(diff),
- one
? ^
+ ore
? ^
- two
- three
? -
+ tree
+ emu