Can I use anonymous function with "static" variables in Python?
Can anonymous function be used with "static" variables in Python?
for example
lambda x: re.compile(r'foobar').match(x)
not that good because it can recompile every time it is called (if it re
runs out of cache), thank you pointers to the caching mechanism).
I can do this without recompiling:
def f(line):
try:
f.c
except:
f.c = re.compile(r'foobar')
return f.c.match(line)
How can I do this with a lambda, without recompiling?
And okay, I don't want to use a helper function to use it inside a lambda. The whole point of using lambda is "anonymity". So yes, lambda is anonymous and self-contained.
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A common trick is to provide a default value for an argument that you are not going to provide.
lambda x, regexobject=re.compile(r'foobar'): regexobject.match(x)
The default is evaluated when it is defined lambda
, not every time it is called.
Instead of using lambda
, I would just clearly define your regexps
regex1 = re.compile(r'foobar')
regex2 = re.compile(r'bazquux')
# etc
then pass the associated method wherever needed. That is, instead of
somefunction(lambda x, regexobject=re.compile(r'foobar'): regexobject.match(x))
using
somefunction(regex1.match)
The use case for an anonymous function is one that will only be called once, so it doesn't make sense to bind a name to it. The fact that you are worried about being re.compile
called multiple times indicates that the functions will be called multiple times.
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