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pythonlambda
Eugene
Eugene

Reputation: 598

python map like object which contains lambda functions

I try create map like object which contains lambda functions:

class Map(object):
    a = lambda x: True

But python assumes a as Map class method and expects what it accept self argument which is Map instance.

Of course I can write

class Map(object):
    @staticmethod
    def a(x):
       return True

But it is too long. Is it possible to make the first class?

Upvotes: 1

Views: 268

Answers (2)

newacct
newacct

Reputation: 122449

It's very unclear what you are asking. The first piece of code correctly does what it is supposed to do -- it sets that function as attribute a of Map.

Map.a(42)

But python assumes a as Map class method

Python doesn't "assume" it is a "class method". It is not a "class method". All variables set in the body of a class declaration become members of the class. What were you expecting?

"Class method" refers to things with the @classmethod decorator. This is different from things with the @staticmethod decorator, and also different from things without either. As is, it is neither a "class method" nor a "static method". You need to understand the differences among all three.

The @staticmethod decorator only affects when you try to call a method on an instance of Map. You did not say you were doing any such thing. When accessing an attribute of class directly and calling it, there is no difference.

Upvotes: 0

Martijn Pieters
Martijn Pieters

Reputation: 1122252

Yes, just apply the @staticmethod decorator manually to the lambda:

class Map(object):
    a = staticmethod(lambda x: True)

or simply give your lambda that required self argument:

class Map(object):
    a = lambda self, x: True

Upvotes: 4

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