[Tutor] Given a string, call a function of that name

boB Stepp robertvstepp at gmail.com
Tue May 16 22:49:50 EDT 2017

My son (Now 13 years old.) is merrily programming away in Python 3 (Of
course!) and has many projects he is working on.  Today he resumed
work on his efforts to create a natural language parser, which he
hopes will enable people to type in commands to a DnD-like game using
natural English.  An ambitious project to be sure!  He asked me if
there was any way that if he identified a word in the user's input
corresponding to one of his functions or methods, if he could use that
word to run a function of the same name.  I said I had done something
once where I used the word as a dictionary key, which was then used to
call the function.  After fumbling around a bit I came up with the
following program for him to play around with:

#!/usr/bin/env python3

def spam(phrase):
    print('spam function said: ', phrase)

def ham(phrase):
    print('ham function said: ', phrase)

def eggs(phrase):
    print('eggs function said: ', phrase)

def get_input():
    function = input('Which do you want:  spam, ham or eggs?\n')
    phrase = input('\nHow do you want your food to be prepared?\n')
    return function, phrase

def check_fcn_input(function):
    valid_fcns = ['spam', 'ham', 'eggs']
    if function in valid_fcns:
        return True
        return False

def run_fcn(function, phrase):
    fcn_dict = {'spam': spam, 'ham': ham, 'eggs': eggs}

def main():
    function, phrase = get_input()
    while not check_fcn_input(function):
        print("You made an invalid food choice!  Let's try this again!")
        function, phrase = get_input()
    run_fcn(function, phrase)

if __name__ == '__main__':

This works, but I cannot but help wondering if there is a more direct
approach?  Given the above three functions spam(), ham() and eggs(),
and given a string 'ham', what is the quickest, most direct way to run
that function?  Or similarly for the other two?

Oh, and I suppose I should ask for a critique of the code as written
for appropriate Python style, proper targeted function use, etc.  I am
always eager to learn!  However, I did not use doc strings for the
functions or write tests.  If I were actually planning on using this
for real, I would have done so.

Hmm.  It bothers me that in check_fcn_input() I have a list valid_fcns
and in run_fcn() I have a dictionary fcn_dict.  These contain
essentially the same information.  Would this be a case for a global
function dictionary (Which I could also use to check for valid
functions.) or perhaps a class which only exists to have this function



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