Geek asks and answers

Embedding "global imports" in a Python function

Short but complete, summary

I want to allow users of my function (factory class) to enter / overwrite global imports when using my function (more detailed explanation of the explanation below). But there are about 10 different variables that can be passed, and it adds several repeating lines to the code. (provided, also makes calling difficult: P) Now I am doing something like the following (just simplifying all this). To make it doable, I use a dummy class, but in the actual script I would use import pkg1, etc. I realized that it was clearer and shorter than the factory class, etc.

class Dummy(object): pass

pkg1, pkg2 = Dummy(), Dummy()
pkg1.average = lambda *args : sum(args) / len(args)
pkg2.get_lengths = lambda *args : map(len, args)


def get_average(*args, **kwargs):
    average = kwargs.get("average") or pkg1.average
    get_lengths = kwargs.get("get_lengths") or pkg2.get_lengths
    return average(*get_lengths(*args))

adjusted_length = lambda *args: map(len, args) + [15]
print get_average([1,2], [10, 4, 5, 6]) == 3 # True
print get_average([1,2], [10, 4, 5, 6], get_lengths=adjusted_length) == 7 # True

Related SO Questions

: Python, , , locals, (1) didn , , (2) , . , , .

( python), , , . ( - python: ` globals` - , ( ) ).

, exec (, - python exec()), , , // ..

, . (: from pkg1 import average AND from pkg2 import get_lengths , ( pkg1 pkg2 , ))

average = pkg1.average
get_lengths = pkg2.get_lengths

def get_average(*args, **kwargs):
    localvars = locals()
    for k in ("get_lengths", "average"):
        if kwargs.get(k, None) and kwargs[k] is not None:
            localvars[k] = kwargs[k]
    return average(*get_lengths(*args))

print get_average([1,2], [10, 4, 5, 6]) == 3 #True
print get_average([1,2], [10, 4, 5, 6], get_lengths=adjusted_length) == 7 # False, is 3

factory ( SQLAlchemy mixin), , SQLAlchemy, ..

, Flask-SQLAlchemy , SQLAlchemy, / (db), SQLAlchemy, .

+5
1

. , , . lists *args, . , get_average.

sorted , Python .

get_average(lists, average=pkg1.average, get_lengths=pkg2.get_lengths):
    return average(*get_lengths(*lists))

print get_average(([1,2], [10, 4, 5, 6]))
print get_average(([1,2], [10, 4, 5, 6]), get_lengths=adjusted_length)

, :

class GetAverageContext(object):
    def __init__(self, average=pkg1.average, get_lengths=pkg2.get_lengths):
        self.average = average
        self.get_lengths = get_lengths

DefaultGetAverageContext = GetAverageContext()

def get_average(lists, context=DefaultGetAverageContext):
    return context.average(*context.get_lengths(*lists))
+2

More articles:


All Articles