Map imported function to a variable

Question

I have some imported functions from package import fizz, buzz and I want to map them to a variable func from a string arg.

class Whatever(object):
    def __init__(self, func_name='fizz'):
        try:
            self.func = vars()[func_name]
        except KeyError:
            print "Bad func_name"
            raise

But vars() only captures the local namespace, and I don't want to allow access to globals(). Any ideas? Or should I just go with if-else logic?

This might be what you're looking for: docs.python.org/3/library/functions.html#exec — Ryan W
– Ryan W, Commented May 10, 2017 at 19:03
Why don't you pass the function directly to the initializer: def __init__(self, func=fizz) — juanpa.arrivillaga
– juanpa.arrivillaga, Commented May 10, 2017 at 19:03
But basically, if you want to access some global name outside the global scope using a string, then you sort of have to use globals, or even worse, something like exec or eval. — juanpa.arrivillaga
– juanpa.arrivillaga, Commented May 10, 2017 at 19:04
Thank you, I'll check out exec and eval. Also thinking I could just create a class attr dict that maps the strings to the imported functions. — BoltzmannBrain
– BoltzmannBrain, Commented May 10, 2017 at 19:12
@juanpa.arrivillaga I'm not passing the function directly b/c I don't have the caller import the functions, but rather they are imported where the class is defined. Are you suggesting this is bad (or nonpythonic)? — BoltzmannBrain
– BoltzmannBrain, Commented May 10, 2017 at 19:13

tdelaney · Accepted Answer · 2017-05-10 19:16:07Z

2

You could use a white list... or in this case, a "white dict"

class Whatever(object):

    allowed = { 'fizz':fizz, 'buzz':buz }

    def __init__(self, func_name='fizz'):
        try:
            self.func = self.allowed[func_name]
        except KeyError:
            print "Bad func_name"
            raise

answered May 10, 2017 at 19:16

tdelaney

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1 Comment

BoltzmannBrain Over a year ago

Thanks, this is what I mentioned in the comments above as a decent alternative.

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