Python: regex search and replace

republicado de http://pythontesting.net/python/regex-search-replace-examples/#in_python

using Python

Search and replace as a filter

I think the most basic form of a search/replace script in python is something like this:

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import fileinput import re for line in fileinput.input():     line = re.sub('foo','bar', line.rstrip())     print(line)

The fileinput module takes care of the stream verses filename input handling.
The re (regex, regular expression) module has sub which handles the search/replace.
The ‘rstrip’ is called on the input just to strip the line of it’s newline, since the next ‘print’ statement is going to add a newline by default.

This handles the case where we don’t want to modify the file.

In place modification of files

A slightly modified script will allow you to modify files, and optionally copy the original file to a backup.

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import fileinput import re for line in fileinput.input(inplace=1, backup='.bak'):     line = re.sub('foo','bar', line.rstrip())     print(line)

If you leave the ‘backup’ flag out, no backup will be made.
As I’ve shown it with backup=’.bak’, an example.txt.bak file will be created.

with a more complex regular expression

Of course, foo and bar don’t have to be so simple.
For example, the markdown issue I have with converting a table of contents to a series of h2 tags, can be solved with the following script.

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import fileinput import re for line in fileinput.input():     line = re.sub(r'\* \[(.*)\]\(#(.*)\)', r'<h2 id="\2">\1</h2>', line.rstrip())     print(line)

Here, I’m looking for things that look like

1 2	* [the label](#the_anchor)

and replacing it with

1 2	<h2 id="the_anchor">the link</h2>