Python - Call a function of an object which is stored in a dict

Question

I have an Class which creates objects that contain a dict of functions. These functions are defined in the class.

class Foo:

    def __init__(self, name, functions):
        self.name = name
        self.functions = functions

    def myFunction1(self):
        print self.name
        return 'foo'

    def myFunction2(self):
        return 'bar'

In another file, I instance an object of the previous class and I want to run one of the functions that is in the dict.

from foo import Foo

myFunctions = Foo.('a name', {0 : Foo.myFunction1, 1 : Foo.myFunction2})

myFunctions.functions[0]()

I have this error: TypeError: unbound method myFunction1() must be called with Foo instance as first argument.

I understand that when I execute the last line, I just call the function without call it with an object of Foo as first argument. But I can not write this:

myFunctions.myFunctions.functions[0]()

How can I call a function of this class which is stored in a dict attribute?

Answer 1

I do not really understand what you are trying to achieve with this functions dictionary, but note that instance.function() is equivalent to Class.function(instance) . In the former, instance is implicitly passed as the self parameter; in the latter, you pass it explicitly.

Thus, you could try the following.

foo = Foo({0 : Foo.myFunction1, 1 : Foo.myFunction2})
print foo.functions[0](foo)

Answer 2

You can call functions as a dictionary like this:

tmp = Foo()
tmp.functions={0:tmp.myFunction1, 1:tmp.myFunction2}
myFunctions = tmp.functions
print myFunctions.functions[0]()

Answer 3

If you need an object method, best way is to write another function that will call the correct function

class Foo:

    def __init__(self, functions):
        self.functions = functions

    def myFunction1(self):
        return 'foo'

    def myFunction2(self):
        return 'bar'

    def run_func(self, func_key, *args, **kwargs):
        func_name = self.functions.get(func_key)
        if func_name and hasattr(self, func_name):
            return getattr(self, func_name)(*args, **kwargs)
        else:
            return None

fun_dict = {0:'myFunction1', 1:'myFunction2'}
a = Foo(fun_dict)
print a.run_func(0)

You can send even arguments in this way.

def myFunction1(self, name):
    return name

print a.run_func(0, "test")

This will print test by the myFunction1

Answer 4

Here is the simplest way to switch between functions:

       dict = {0 : Foo.myFunction1(), 1 : Foo.myFunction2()}
       function = fn_dict.get(0)
       function()

Answer 5

For the next reader, I'd suggest you to read https://stackoverflow.com/a/32284348/13213188

Helps working with class functions stored in dicts, no need to create any instance