CODEWITHSUNDEEP
python
Wizzard
Wizzard

Reputation: 12702

Dynamically import and create class instance

With my python application, I have 40 modules (classes) which contain a parser for some text. In my function I only want to instanciate and use a particular module. These are all sorted in the database.

I am at the point now where I know my parser, and have both the python file name and class I want to import and create

However.... How do you actually do this in python?

eg;

file_name = 'lex_parser'
class_name = 'LexParser'

how can I do....

from {file_name} import {class_name}
Parser = {class_name}()

Follow what I mean?

Upvotes: 0

Views: 2329

Answers (2)

yak
yak

Reputation: 9041

Try this:

file_name = 'lex_parser'
class_name = 'LexParser'

Parser = getattr(__import__(file_name), class_name)

Note that file_name must not contain .py.

This won't work if the module is within a package because __import__ would return the top level package. In that case you can do this:

import sys

file_name = 'parsers.lex_parser'
class_name = 'LexParser'

__import__(file_name)
Parser = getattr(sys.modules[file_name], class_name)

This will work in both cases and is recommeded by the __import__ function documentation.

In both examples Parser is a class which you have to instantiate as normally:

parser = Parser()

Upvotes: 6

Some programmer dude
Some programmer dude

Reputation: 409166

How about something like this:

module = __import__('my_module')
if hasattr(module, 'ClassName'):
    ClassName = module.ClassName
    my_object = ClassName()

Upvotes: 3

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