How to call a function programmatically in Python specifying a module programmatically also?

Question

I can't use this

import foo
method_to_call = getattr(foo, 'bar')
result = method_to_call()

because module name is hardcoded and I can't use this

module = __import__('foo')
func = getattr(module, 'bar')
func()

because module is nested.

I tried this

customer = 'jci'
module = __import__('customer.{customer_name}.gt'.format(customer_name=customer_name)) # AttributeError: module 'customer' has no attribute 'get_gt'
#module = __import__('customer.{customer_name}'.format(customer_name=customer_name), fromlist=['gt']) # AttributeError: module 'customer.jci' has no attribute 'get_gt'
#module = __import__('customer.{customer_name}.gt'.format(customer_name=customer_name), fromlist=[]) # AttributeError: module 'customer' has no attribute 'get_gt'
func = getattr(module, 'get_gt')
gt = func()

but failed with errors, specified in comment along with each variant.

get_gt() is a function inside gt.py file inside customer/jci directory. Each directory has empty __init__.py inside.

The following hardcoded code works:

import customer.jci.gt as g
gt = g.get_gt()

How to overcome?

Bakuriu · Accepted Answer · 2018-12-12 14:32:14Z

3

What you want is importlib.import_module.

Note that __import__ does handle dotted names but it returns the parent package, not the last child.

Proof:

>>> http = __import__('http.client')
>>> http.client   # the client submodule was imported
<module 'http.client' from '/usr/lib/python3.6/http/client.py'>
>>> # without specifying the .client in the name the submodule is not imported
>>> __import__('http').client
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'http' has no attribute 'client'

import_module instead returns the child module, which is what most people expect:

>>> importlib.import_module('http.client')
<module 'http.client' from '/usr/lib/python3.6/http/client.py'>

answered Dec 12, 2018 at 14:32

Bakuriu

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3 Comments

Mauro Baraldi Over a year ago

This is a good approach, anyway if his package has a class and he wants the method from class, he will return to initial case.

Bakuriu Over a year ago

@MauroBaraldi I don't understand what you are saying. There is no one function where you can specify package.module.class.method and get a reference to the method. The OP already knows how to retriever an attribute using getattr, the only issue they had is the one I explained in the answer.

Mauro Baraldi Over a year ago

You're right @Bakuriu, I have misunderstood the question. Sorry :-(

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