CODEWITHSUNDEEP
pythonmethodsdictionary
Remi.b
Remi.b

Reputation: 18219

Using a dictionary to control the flow of methods

I have a class Population that contains several method.

According to an input I want the run the method on an instance of the class Population in a given order.

To be a bit more accurate in what I am trying to achieve is quite the same than using is something like that:

stuff = input(" enter stuff ")

dico = {'stuff1':functionA, 'stuff2':functionC, 'stuff3':functionB, 'stuff4':functionD}

dico[stuff]()

Except that the functionA, functionB etc... are methods and not functions:

order_type = 'a'
class Population (object):
    def __init__(self,a):
        self.a = a

    def method1 (self):
        self.a = self.a*2
        return self

    def method2 (self):
        self.a += 2
        return self

    def method3 (self,b):
        self.a = self.a + b
        return self

if order_type=='a':
    order = {1:method1, 2:method2, 3:method3}
elif order_type=='b':
    order = {1:method2, 2:method1, 3:method3}
else :
    order = {1:method3, 2:method2, 3:method1}

my_pop = Population(3)

while iteration < 100:
    iteration +=1
    for i in range(len(order)):
        method_to_use = order[i]
        my_pop.method_to_use() # But obviously it doesn't work!

Hope I've made my question clear enough! Note that one of my method need two arguments

Upvotes: 1

Views: 158

Answers (3)

Bakuriu
Bakuriu

Reputation: 101929

Pass the instance explicitly as first argument:

method_to_use = order[i]
method_to_use(my_pop)

Full working code:

order_type = 'a'
class Population (object):
    def __init__(self,a):
        self.a = a

    def method1 (self):
        self.a = self.a*2
        return self

    def method2 (self):
        self.a += 2
        return self

    def method3 (self):
        self.a = 0
        return self

if order_type=='a':
    order = [Population.method1, Population.method2, Population.method3]
elif order_type=='b':
    order = [Population.method2, Population.method1, Population.method3]
else :
    order = [Population.method3, Population.method2, Population.method1]

my_pop = Population(3)

while iteration < 100:
    iteration +=1
    for method_to_use in order:
        method_to_use(my_pop)

If you want to pass more than one argument, simply use the *args syntax:

if order_type=='a':
    order = [Population.method1, Population.method2, Population.method3]
    arguments = [(), (), (the_argument,)]
elif order_type=='b':
    order = [Population.method2, Population.method1, Population.method3]
    arguments = [(), (), (the_argument,)]
else :
    order = [Population.method3, Population.method2, Population.method1]
    arguments = [(the_argument, ), (), ()]

my_pop = Population(3)

while iteration < 100:
    iteration +=1
    for method_to_use, args in zip(order, arguments):
        method_to_use(my_pop, *args)

The () is an empty tuple, hence *args will expand to no additional arguments, while (the_argument,) is a 1-element tuple that will pass the argument to the method.

Upvotes: 2

Saullo G. P. Castro
Saullo G. P. Castro

Reputation: 58895

You can use operator.methodcaller:

from operator import methodcaller
method_to_use = methodcaller('method' + str(i))
method_to_use(my_pop)

Upvotes: 2

Ashwini Chaudhary
Ashwini Chaudhary

Reputation: 250941

Use getattr:

order = {1:'method1', 2:'method2', 3:'method3'} #values are strings
...
method_to_use = order[i]
getattr(mypop, method_to_use)()

Upvotes: 2

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