python-rex 0.4

Python regular expressions for humans

Welcome to python-Rex

Python Rex is regular expressions for humans. (Rex is also abbreviation from re X tended).

Rex is for the re standard module as requests is for urllib module.

Rex also is latin for “king”, and the king of regular expressions is Perl. So Rex API tries to mimic at least some Perl’s idioms.

Supported Python versions: 2.6, 2.7, 3.3

Installation

pip install python-rex

or

pip install -e git+https://github.com/cypreess/python-rex.git#egg=rex-dev

There are no external dependencies.

from rex import rex

Quickstart

Do that:

from rex import rex
print ("Your ticket number: XyZ-1047. Have fun!" == rex("/[a-z]{3}-(\d{4})/i"))[1]

instead of doing that:

import re
regex = re.compile("[a-z]{3}-(\d{4})", flags=re.IGNORECASE)
m = regex.search("Your ticket number: XyZ-1047. Have fun!")

if m is not None:
   print m.group(1)
else:
   print None

# or in shorter way
print m.group(1) if m else None

(both should print 1047).

Docs

So far Rex supports:

• simple matching (first match),

• substitution,

• all python re flags.

Matching

The most obvious usage - test condition by matching to string:

if 'This is a dog' == rex('/dog/'):
    print 'Oh yeah'

or:

if 'My lucky 777 number' == rex('/[0-9]+/'):
    print 'Number found'

You can use Perl notation and prepend m character to your search:

if 'My lucky 777 number' == rex('m/[0-9]+/'):
    print 'Number found'

but you can also simply check your match:

if ('My lucky 777 number' == rex('m/[0-9]+/'))[0] == '777':
    print 'Number found'

or even groups:

if ('My lucky 777 number' == rex('m/(?P<number>[0-9]+)/'))['number'] == '777':
    print 'Number found'

Remember a mess with re module when it does not match anything? Rex won’t let you down, it will kindly return None for whatever you ask:

>>> print ('My lucky 777 number' == rex('m/(?P<number>[0-9]+)/'))['no_such_group']
None

>>> print ("I don't tell you my lucky number" == rex('m/(?P<number>[0-9]+)/'))['number']
None

Substituting

Substitution can be made by prefixing pattern with s character (like in perl expression):

>>> print "This is a cat" == rex('s/CAT/dog/i')
This is a dog

Flags

Every Rex pattern as in Perl patterns allows to suffix some flags, e.g. rex('/pattern/iu') for enabling i and u flag. Rex supports all standard python re flags:

• d - re.DEBUG

• i - re.IGNORECASE

• l - re.LOCALE

• m - re.MULTILINE

• s - re.DOTALL

• u - re.UNICODE

• x - re.VERBOSE

Caching

Rex caches all patterns so reusing patterns is super fast. You can always clear Rex cache by calling rex_clear_cache() or disable caching for specific patterns rex('/pattern/', cache=False).

Rex for orthodox

If you are so orthodox pythonist that couldn’t leave with overloaded == operator syntax in your codebase, you can use “orthodox mode” of rex. Just put the string to match/substitute against as a second argument:

>>> bool(rex("/dog/", "This is a dog"))
True
>>> rex("s/cat/dog/", "This is a cat")
'This is a dog'

Additionally Rex objects are callable. This is especially useful in situations where you need to process many values against the same regular expression:

>>> my_re = rex("/foo/")
>>> for thing in ["foobar", "bar", "barfoo"]:
...     print bool(my_re(thing))
True
False
True