plainbox.impl.censoREd
– working around frustrating stuff¶
This module is the result of an evening of frustration caused by the need to support Python 3.2 and a failing doctest that exercises, unintentionally, the behavior of the compiled regular expression object’s __repr__() method. That should be something we can fix, right? Let’s not get crazy here:
>>> import re
>>> sre_cls = type(re.compile(""))
>>> sre_cls
<class '_sre.SRE_Pattern'>
Aha, we have a nice type. It’s only got a broken __repr__ method that sucks. But this is Python, we can fix that? Right?
>>> sre_cls.__repr__ = (
... lambda self: "re.compile({!r})".format(self.pattern))
...
Traceback (most recent call last):
...
TypeError: can't set attributes of built-in/extension
type '_sre.SRE_Pattern'
Traceback (most recent call last):
...
TypeError: can't set attributes of built-in/extension
Hmm, okay, so let’s try something else:
>>> class Pattern(sre_cls):
... def __repr__(self):
... return "re.compile({!r})".format(self.pattern)
Traceback (most recent call last):
...
TypeError: type '_sre.SRE_Pattern' is not an acceptable base type
Traceback (most recent call last):
...
TypeError: type '_sre.SRE_Pattern' is not an acceptable base type
Sigh, denial, anger, bargaining, depression, acceptance https://twitter.com/zygoon/status/560088469192843264
The last resort, aka, the proxy approach. Let’s use a bit of magic to work around the problem. This way we won’t have to subclass or override anything.
-
plainbox.impl.censoREd.
PatternProxy
[source]¶ A proxy that overrides the __repr__() to match what Python 3.3+ providers on the internal object representing a compiled regular expression.
>>> import re >>> sre_cls = type(re.compile("")) >>> pattern = PatternProxy(re.compile("profanity"))
Can we have a repr() like in Python3.4 please?
>>> pattern re.compile('profanity')
Does it still work like a normal pattern object?
>>> pattern.match("profanity") is not None True >>> pattern.match("love") is not None False
Yes (gets another drink).