Python - Calling a function of a module by using its name (a string)

objectpython

What is the best way to go about calling a function given a string with the function's name in a Python program. For example, let's say that I have a module foo, and I have a string whose content is "bar". What is the best way to call foo.bar()?

I need to get the return value of the function, which is why I don't just use eval. I figured out how to do it by using eval to define a temp function that returns the result of that function call, but I'm hoping that there is a more elegant way to do this.

Best Solution

Assuming module foo with method bar:

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

You could shorten lines 2 and 3 to:

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

if that makes more sense for your use case.

You can use getattr in this fashion on class instance bound methods, module-level methods, class methods... the list goes on.

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Python - What’s the canonical way to check for type in Python

To check if o is an instance of str or any subclass of str, use isinstance (this would be the "canonical" way):

if isinstance(o, str):

To check if the type of o is exactly str (exclude subclasses):

if type(o) is str:

The following also works, and can be useful in some cases:

if issubclass(type(o), str):

See Built-in Functions in the Python Library Reference for relevant information.

One more note: in this case, if you're using Python 2, you may actually want to use:

if isinstance(o, basestring):

because this will also catch Unicode strings (unicode is not a subclass of str; both str and unicode are subclasses of basestring). Note that basestring no longer exists in Python 3, where there's a strict separation of strings (str) and binary data (bytes).

Alternatively, isinstance accepts a tuple of classes. This will return True if o is an instance of any subclass of any of (str, unicode):

if isinstance(o, (str, unicode)):

Python - How to get a function name as a string

my_function.__name__

Using __name__ is the preferred method as it applies uniformly. Unlike func_name, it works on built-in functions as well:

>>> import time
>>> time.time.func_name
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: 'builtin_function_or_method' object has no attribute 'func_name'
>>> time.time.__name__ 
'time'

Also the double underscores indicate to the reader this is a special attribute. As a bonus, classes and modules have a __name__ attribute too, so you only have remember one special name.

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Python - What’s the canonical way to check for type in Python

Python - How to get a function name as a string

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