On 08Aug2017 08:39, Alan Gauld <alan.ga...@yahoo.co.uk> wrote:
(1) There are very, very few good uses for static methods in Python. If
you think you need a static method, you probably could just use a
regular module-level function.
Amen to that, I try to avoid staticmethods... and so far
have never found a valid use for one. I treat them as a
piece of legacy from earlier versions, prior to classmethods.
I use them a bit for things that _could_ be module level functions, but using a
static method lets me (a) associate if with a class and (b) one gets access to
the method when one imports the class. So one can write code like this:
from my_module import SomeDataFormat
with open(datafile) as f:
header_info = SomeDataFormat.parse_header(f)
and the module's SomeDataFormat class might have:
class Foo:
@staticmethod
def parse_header(f):
# decode the header structure and return info about it
That could easily be a standalone module function, but if the header record is
a specific to the class then one can expose the parser function as a static
method: it comes in with the class when it is imported, and it is clear that
the parser is for what the class manages. It lets you avoid
cumber_long_function_names because the "SomeDataFormat." contributes to the
description.
I've also used them for factories, but think a class method is better. Thus:
class Foo:
def __init__(self, x, y, z):
self.x = x
self.y = y
self.z = z
@staticmethod
def from_point(p):
return Foo(p.x, p.y, p.z)
so that one can make a Foo directly:
f = Foo(1,2,3)
or from some hypothetical "point" object:
f = Foo.from_point(p)
But arguably this would be better as a class method anyway:
@classmethod
def from_point(klass, p):
return klass(p.x, p.y, p.z)
because it lets you subclass Foo:
class Bah(Foo):
and call Bah.from_point(p) for free, and it will make a Bah instead of a Foo
because it gets the class as "klass".
Cheers,
Cameron Simpson <c...@cskk.id.au> (formerly c...@zip.com.au)
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