For example,
I have my class, MyClass
and I want to be able to instantiate it as MyClass((1, 2)) but MyClass(1, 2) should also result in the same. Is it also possible to instantiate it by writing MyClass[1, 2] by some way?
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2 Answers
def __init__(arg1, arg2=None):
if arg2 is None:
construct_one_way()
else:
do_something_different()
You can technically get MyClass[1, 2] to work with a custom metaclass, but anyone reading your code will hate you. Brackets are for element access.
If you want to be That Guy With The Unmaintainable Code, here's the metaclass option:
class DontDoThis(type):
def __getitem__(self, arg):
return self(arg)
class SeriouslyDont(object):
__metaclass__ = DontDoThis
def __init__(self, arg1, arg2=None):
if arg2 is None:
arg1, arg2 = arg1
self.arg1 = arg1
self.arg2 = arg2
Demonstration:
>>> SeriouslyDont[1, 2]
<__main__.SeriouslyDont object at 0x000000000212D0F0>
5 Comments
NPE
Love the cleverness, but seriously hope this won't make it into any sort of real-world code! :-)
NPE
@JonClements: Wait,
+2 - (-1) is +3 :)
Jon Clements
The English language use of the hyphen... etc... @NPE :)
NPE
@JonClements: I'll buy that. :) Anyway, bedtime. Night-night.
adarsh
Thank you for the well documented warnings :)
No, you can't do that in any half-sane way. The nearest thing syntactically that I can think of is:
class X(object):
def __init__(self, x, y):
print x, y
X(1, 2)
X(*(1, 2))
X(*[1, 2])
There are some legitimate uses for this. However, they are pretty limited.
4 Comments
adarsh
Of course this would work, but this is not I'm looking for. I'm not sure but maybe metaclasses seem that it might help and I've been reading up on them but I can't quite figure out how
Jon Clements
@adarsh then what perverse language evasion are you looking for?
adarsh
I am looking for something that makes more intuitive sense for representing mathematical intervals
NPE
@adarsh: In which case presumably you'd also want to represent half-open intervals? That would be a complete non-starter...