grimace: a fluent regular expression generator in Python

Ben Last benlast at gmail.com
Tue Jul 16 00:21:05 CEST 2013


Hi all

I'd be interested in comments on a fluent regular expression generator I've
been playing with (inspired by the frustrations of a friend of mine who's
learning).

The general use case is to be able to construct RE strings such as:

r'^\(\d{3,3}\)-{1,1}\d{3,3}\-{1,1}\d{4,4}$' (intended to match North
American phone number)

as:

from grimace import RE
north_american_number_re = (RE().start

.literal('(').followed_by.exactly(3).digits.then.literal(')')

.then.one.literal("-").then.exactly(3).digits

.then.one.dash.followed_by.exactly(4).digits.then.end
                                    .as_string())

The intent is to provide clarity: since the strings would normally be
generated and compiled when a module is first imported, there's minimal
overhead.

It's on github at https://github.com/benlast/grimace and the first blog
post that explains it is here: http://benlast.livejournal.com/30871.html (I've
added to it since then).

Tests are the best explanation, and they're in the __init__ at the end so
that they're self-executing if the init is executed.

I'm thinking about other features to implement, and more use cases would be
welcome.

Cheers
ben
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