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From: Ben Last <benlast@gmail.com>
Date: Tue, 16 Jul 2013 06:21:05 +0800
Subject: grimace: a fluent regular expression generator in Python
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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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<div dir=3D"ltr">Hi all<div><br></div><div>I&#39;d be interested in comment=
s on a fluent regular expression generator I&#39;ve been playing with (insp=
ired by the frustrations of a friend of mine who&#39;s learning).</div><div=
>

<br></div><div>The general use case is to be able to construct RE strings s=
uch as:</div><div><br></div><div>r&#39;^\(\d{3,3}\)-{1,1}\d{3,3}\-{1,1}\d{4=
,4}$&#39; (intended to match North American phone number)<br></div><div>

<br></div><div>as:</div><div><br></div><div>from grimace import RE</div><di=
v><div>north_american_number_re =3D (RE().start</div><div>=C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 .literal(&#39;(&#39;).followed_by.exactl=
y(3).digits.then.literal(&#39;)&#39;)</div>

<div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 .then.one.literal(&=
quot;-&quot;).then.exactly(3).digits</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 .then.one.dash.followed_by.exactly(4).digits.then.=
end</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 .as_stri=
ng())</div>

</div><div><br></div><div>The intent is to provide clarity: since the strin=
gs would normally be generated and compiled when a module is first imported=
, there&#39;s minimal overhead.</div><div><br></div><div>It&#39;s on github=
 at=C2=A0<a href=3D"https://github.com/benlast/grimace">https://github.com/=
benlast/grimace</a>=C2=A0and the first blog post that explains it is here:=
=C2=A0<a href=3D"http://benlast.livejournal.com/30871.html">http://benlast.=
livejournal.com/30871.html</a>=C2=A0(I&#39;ve added to it since then).</div=
>

<div><br></div><div>Tests are the best explanation, and they&#39;re in the =
__init__ at the end so that they&#39;re self-executing if the init is execu=
ted.</div><div><br></div><div>I&#39;m thinking about other features to impl=
ement, and more use cases would be welcome.</div>

<div><br></div><div>Cheers</div><div>ben</div><div><br></div></div>

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