Storing Functions in Dictionary [Python]

Question

I'm currently building an application where I need to iterate over a series of steps that do largely the same thing, save a very small amount of code (~15 lines). The number of steps will vary depending on how the project is configured, so it seems kind of silly for me to create a separate function for each potential instance.

In JavaScript, I would do something like this:

var switches = [true, true, false, true];

var holder = {
    0: function() { /* do step0 */ }
    1: function() { /* do step1 */ }
    2: function() { /* do step2 */ }
    3: function() { /* do step3 */ }
    // ...etc...
}

for (var i = 0; i < switches.length; i++)
    if (switches[i])
        holder[i]();

Is there a way to do something similar to this in python? The only thing I can think of is something like this:

switches = [True, True, False, True]

class Holder(object):
    @staticmethod
    def do_0():
        # do step0

    @staticmethod
    def do_1():
        # do step 1

    # ...etc...

    def __repr__(self):
        return [self.do_0, self.do_1, ...]

for action in Holder:
    action()

This just seems terribly inefficient if I have any significant number of steps. Is there any better way to go about this?

Answer 1

You can do this as follows:

# define your functions
def fun1():
    print("fun1")

def fun2():
    print("fun2")

def fun3():
    print("fun3")


switches = [True, False, True];

# put them in a list (list makes more sense than dict based on your example)
func_list = [fun1, fun2, fun3]

# iterate over switches and corresponding functions, and execute 
# functions when s is True    
for s,f in zip(switches, func_list):
    if s: f() 

This is one way only. There are many others. e.g. using lambdas, dict as you wanted, etc.

To use lambdas if your functions are one line only, you can do:

func_list = [lambda: print("lambda1"), 
             lambda: print("lambda2"), 
             lambda: print("lambda1")]

Answer 2

It looks like there isn't a way to do this in Python, a design decision made intentionally since it was dismissed as un-Pythonic. Oh well, it looks like I'm stuck defining the methods and then manually adding them to a list to iterate through.

Source: https://softwareengineering.stackexchange.com/a/99245