Call functions from list - Python

Question

I have a list of strings, and I want to call a function for every character in a string. When I assign variables to each function I do not want them to run, I only want to call them when iterating over the string. Here is my code:

import random

def make_s():
    result = ''

    V = make_v
    C = make_c
    P = make_p
    B = make_b

    structs = ['VPCVBCC', 'VCVVC', 'VVPCC', 'VCVBCC', 'VPCCVBC', 'VCVCC', 'VPCBC', \
            'VVPCVBCC', 'VCVC', 'VPCVVBC']

    struct = random.choice(structs)

    for elem in struct:
        /* Call function defined above and add the result to the result string */
        result += elem()

    return result

What's the best way to go about doing this?

Many thanks :)

Using dict instead of list might be easier to implement

David Zemens
– David Zemens

2016-12-07 17:18:15 +00:00
Commented Dec 7, 2016 at 17:18 — David Zemens
– David Zemens, Commented Dec 7, 2016 at 17:18

turbulencetoo · Accepted Answer · 2016-12-07 17:21:50Z

9

You're pretty close. You should just map your characters to the functions, as opposed to assigning to specific variables.

import random

def make_s():
    result = ''

    # Here we have a mapping between the characters you see,
    # and the functions you want to call.
    my_funcs = {"V": make_v,
                "C": make_c,
                "P": make_p,
                "B": make_b}

    structs = ['VPCVBCC', 'VCVVC', 'VVPCC', 'VCVBCC', 'VPCCVBC', 'VCVCC', 'VPCBC', \
            'VVPCVBCC', 'VCVC', 'VPCVVBC']

    struct = random.choice(structs)

    for elem in struct:
        # Lookup the function in your dictionary
        func_to_call = my_funcs[elem]
        # And call it!
        result += func_to_call()

    return result

answered Dec 7, 2016 at 17:21

turbulencetoo

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3 Comments

turbulencetoo Over a year ago

It's often hard to try to figure out (in code) which variable name is assigned to which function. Turning a "V" charcter into 'whichever object my variable "V" points to' is generally hacky and can be avoided by a dict just like this.

David Zemens Over a year ago

You could save a few steps by doing my_funcs = {'V': make_v(), 'C': make_c(), 'P': make_p(), 'B': make_b()} , then it's just for elem in struct: result+=my_funcs[elem]

turbulencetoo Over a year ago

In languages like python you can figure out variable names at runtime in a somehwat hacky way, but in other languages it cant be done at all.

David Zemens · Accepted Answer · 2016-12-07 18:29:19Z

3

Similar approach using dictionary to map characters to function calls, a bit more concise using list comprehension & the string join function:

import random
def make_s():
    fDict = {'V': make_v(), 'C': make_c(), 'P': make_p(), 'B': make_b()}
    structs = ['VPCVBCC', 'VCVVC', 'VVPCC', 'VCVBCC', 'VPCCVBC', 'VCVCC', 'VPCBC', \
            'VVPCVBCC', 'VCVC', 'VPCVVBC']
    struct = random.choice(structs)
    return ''.join([fDict[elem] for elem in struct])

edited Dec 7, 2016 at 18:29

answered Dec 7, 2016 at 17:28

David Zemens

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2 Comments

ggordon Over a year ago

Thanks, should have pointed out that the function produces a different output every time it's run, so above method works better

David Zemens Over a year ago

Ahhh I might've went a little too far with it :) Revised to isolate the random.choice(structs) so that it's not part of the comprehension (though I don't think that affects output) and I think this should be functionally same as the other answer. Otherwise, not sure what distinction you're making about "different output every time it's run". Cheers

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