Importing using string in Python

Question

Short version:

Say I have a string str and a file functions.py from which I would like to import a method whose name is stored in str.

How do I go about it? I would like something like:

from functions.py import str

but have str evaluated and not to import the method 'str' (which doesn't exist).

After some googling I came as close (I hope) as:

func_name = str
_tmp = __import__('functions.py', globals(), locals(), ['func_name'], -1)
func = ???? <what to put here?>

Thanks in advance.

EDIT: TMI.

Note you should import functions and not functions.py.

Jasmijn
– Jasmijn

2011-10-16 19:54:26 +00:00
Commented Oct 16, 2011 at 19:54 — Jasmijn
– Jasmijn, Commented Oct 16, 2011 at 19:54

David Heffernan · Accepted Answer · 2011-10-16 16:48:48Z

5

Assuming your code to import the module into _tmp works then the final step is simply:

func = getattr(_tmp, func_name)

answered Oct 16, 2011 at 16:48

David Heffernan

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Comments

interjay · Accepted Answer · 2011-10-16 16:48:28Z

1

The getattr method gives you an attribute of a given object. Since global functions are attributes of the module they are in, you can use this:

import functions

funcName = 'doSomething'
f = getattr(functions, funcName)
f(123)

There is no need to use __import__, as that's usually needed only when you don't know the module name in advance.

answered Oct 16, 2011 at 16:48

interjay

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Comments

Paul Manta · Accepted Answer · 2011-10-16 16:55:52Z

0

If your goal is to save memory by only importing the functions you need, don't bother; even if you used the from ... import ... construct, Python still imports the whole module, just that it only adds to the current dictionary those members that you explicitly requested (the others are still in memory, just that they're not accessible directly).

With that in mind, I would do something along these lines:

import functions
the_name = self.name.lower() + str(i)
the_func = getattr(functions, the_name)

edited Oct 16, 2011 at 16:55

answered Oct 16, 2011 at 16:50

Paul Manta

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2 Comments

Mark Dickinson Over a year ago

TypeError: 'module' object is not subscriptable

Paul Manta Over a year ago

@Mark Ah, right. You forget the little bits after not using the language for some time. :)

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