Pass method as a parameter on python

Question

Can I pass a method as a parameter on python? I want to do things like, for example, if anything is an instance of an object w/has foo method:

def access_to(class=anything, method="foo"): return class.method

(Note is obvious that Anything instance doesn't have the attribute 'method', and Ill get an AttributeError).

• sebach1: I dont want to call a function as a method of the class object, the function I wanna make is outside that.

Answer 1

Uses getattr if you want to get the method from a string parameter.

class A:
 def foo(self):
 print("foo")
def access_to(c, method="foo"):
 return getattr(c, method)
a = A()
b = 5
access_to(a)()
access_to(b)()

It prints foo for a, then it raises error for b

I have to say that I recommend not to abuse this type of functions unless you have to for some specific reasons.

• sebach1: Excellent. Thanks u! (ps: its a very particular case, ive to handle with too large named methods (i didnt built that) and ive to call a function which uses these methods too much time. Thanks u)

Answer 2

You certainly can pass a method as a parameter to a function in Python. In my example below, I created a class (MyClass) which has two methods: isOdd and filterArray. I also created an isEven function outside of MyClass. The filterArray takes two parameters - an array and a function that returns True or False - and uses the method passed as a parameter to filter the array.

Additionally, you can pass lambda functions as parameter, which is like creating a function on the fly without having to write a function declaration.

def isEven(num):
 return num % 2 == 0
class MyClass:
 def isOdd(self, num):
 return not isEven(num)
 def filterArray(self, arr, method):
 return [item for item in arr if method(item)]
myArr = list(range(10)) # [0, 1, 2, ... 9]
myClass = MyClass()
print(myClass.filterArray(myArr, isEven))
print(myClass.filterArray(myArr, myClass.isOdd))
print(myClass.filterArray(myArr, lambda x: x % 3 == 0))

Output:

[0, 2, 4, 6, 8]
[1, 3, 5, 7, 9]
[0, 3, 6, 9]