is there a way to bind parameter to a function variable in python? [duplicate]

Question

Consider the following example:

class foo:
    def __init__(self):
        print ("Constructor")
    def testMethod(self,val):
        print ("Hello " + val)
    def test(self):
        ptr = self.testMethod("Joe") <---- Anyway instead of calling self.testMethod with parameter "Joe" I could simple bind the parameter Joe to a variable ?
        ptr()

k = foo()
k.test()

In the defintion test is it possible for me to create a variable which when called calls the method self.testMethod with the parameter "Joe" ?

Why is this a downvote now ? Anyway i could improve this ? Downvoting without a clue isnt really productive — James Franco
– James Franco, Commented Jul 28, 2016 at 22:04
You mean something like: def test(self, name): ptr=self.testMethod(name) ? Then you can call k.test("Joe") — marcanuy
– marcanuy, Commented Jul 28, 2016 at 22:07
You mean like from functools import partial, then self.callable = partial(self.testMethod, 'Joe')? — Martijn Pieters
– Martijn Pieters, Commented Jul 28, 2016 at 22:10
yes partial is what I am looking equivalent to std::bind in C++ — James Franco
– James Franco, Commented Jul 28, 2016 at 22:11
I would love to know why someone gave me a downvote though on a totally logical question — James Franco
– James Franco, Commented Jul 28, 2016 at 22:16

Martijn Pieters · Accepted Answer · 2016-07-28 22:12:24Z

1

Either use a functools.partial() object or a lambda expression:

from functools import partial

ptr = partial(self.testMethod, 'Joe')

or

ptr = lambda: self.testMethod('Joe')

answered Jul 28, 2016 at 22:12

Martijn Pieters

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3 Comments

James Franco Over a year ago

Thats exactly what i was looking for thank you. Marked as the answer

Martijn Pieters Over a year ago

It appears you marked the other answer, actually. That's your choice entirely but your comment is confusing in that case :-)

James Franco Over a year ago

Sorry abt that. Thanks for letting me know

Andy Hayden · Accepted Answer · 2016-07-28 22:06:47Z

1

You could pass a name to the constructor (and store it on the class instance), this is then accessible to methods:

class Foo:
    def __init__(self, name):
        print("Constructor")
        self.name = name

    def testMethod(self):
        print("Hello " + self.name)

    def test(self):
        self.testMethod()

As follows:

k = Foo("Joe")
k.test()          # prints: Hello Joe

answered Jul 28, 2016 at 22:06

Andy Hayden

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1 Comment

James Franco Over a year ago

Not really. I am looking for binding functionality. I dont want any other approach. The code i just posted is a simple example.

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