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


How do I call a function, using a string with the function’s name? For example:

import foo
func_name = "bar"
call(foo, func_name)  # calls
Asked By: ricree



Given a module foo with method bar:

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

getattr can similarly be used on class instance bound methods, module-level methods, class methods… the list goes on.

Answered By: Patrick Johnmeyer

Based on Patrick’s solution, to get the module dynamically as well, import it using:

module = __import__('foo')
func = getattr(module, 'bar')
Answered By: HS.
  • Using locals(), which returns a dictionary with the current local symbol table:

  • Using globals(), which returns a dictionary with the global symbol table:

Answered By: sastanin

For what it’s worth, if you needed to pass the function (or class) name and app name as a string, then you could do this:

myFnName  = "MyFn"
myAppName = "MyApp"
app = sys.modules[myAppName]
fn  = getattr(app,myFnName)
Answered By: trubliphone

Just a simple contribution. If the class that we need to instance is in the same file, we can use something like this:

# Get class from globals and create an instance
m = globals()['our_class']()

# Get the function (from the instance) that we need to call
func = getattr(m, 'function_name')

# Call it

For example:

class A:
    def __init__(self):

    def sampleFunc(self, arg):
        print('you called sampleFunc({})'.format(arg))

m = globals()['A']()
func = getattr(m, 'sampleFunc')
func('sample arg')

# Sample, all on one line
getattr(globals()['A'](), 'sampleFunc')('sample arg')

And, if not a class:

def sampleFunc(arg):
    print('you called sampleFunc({})'.format(arg))

globals()['sampleFunc']('sample arg')
Answered By: Sourcegeek

none of what was suggested helped me. I did discover this though.

<object>.__getattribute__(<string name>)(<params>)

I am using python 2.66

Hope this helps

Answered By: Natdrip

Given a string, with a complete python path to a function, this is how I went about getting the result of said function:

import importlib
function_string = 'mypackage.mymodule.myfunc'
mod_name, func_name = function_string.rsplit('.',1)
mod = importlib.import_module(mod_name)
func = getattr(mod, func_name)
result = func()
Answered By: ferrouswheel

The answer (I hope) no one ever wanted

Eval like behavior

getattr(locals().get("foo") or globals().get("foo"), "bar")()

Why not add auto-importing

    locals().get("foo") or 
    globals().get("foo") or

In case we have extra dictionaries we want to check

getattr(next((x for x in (f("foo") for f in 
                          [locals().get, globals().get, 
                           self.__dict__.get, __import__]) 
              if x)),

We need to go deeper

getattr(next((x for x in (f("foo") for f in 
              ([locals().get, globals().get, self.__dict__.get] +
               [d.get for d in (list(dd.values()) for dd in 
                                if isinstance(dd,dict))
                if isinstance(d,dict)] + 
        if x)),
Answered By: 00500005

The best answer according to the Python programming FAQ would be:

functions = {'myfoo':}

mystring = 'myfoo'
if mystring in functions:

The primary advantage of this technique is that the strings do not need to match the names of the functions. This is also the primary technique used to emulate a case construct

Answered By: user3946687

Try this. While this still uses eval, it only uses it to summon the function from the current context. Then, you have the real function to use as you wish.

The main benefit for me from this is that you will get any eval-related errors at the point of summoning the function. Then you will get only the function-related errors when you call.

def say_hello(name):
    print 'Hello {}!'.format(name)

# get the function by name
method_name = 'say_hello'
method = eval(method_name)

# call it like a regular function later
args = ['friend']
kwargs = {}
method(*args, **kwargs)
Answered By: tvt173

As this question How to dynamically call methods within a class using method-name assignment to a variable [duplicate] marked as a duplicate as this one, I am posting a related answer here:

The scenario is, a method in a class want to call another method on the same class dynamically, I have added some details to original example which offers some wider scenario and clarity:

class MyClass:
    def __init__(self, i):
        self.i = i

    def get(self):
        func = getattr(MyClass, 'function{}'.format(self.i))
        func(self, 12)   # This one will work
        # self.func(12)    # But this does NOT work.

    def function1(self, p1):
        print('function1: {}'.format(p1))
        # do other stuff

    def function2(self, p1):
        print('function2: {}'.format(p1))
        # do other stuff

if __name__ == "__main__":
    class1 = MyClass(1)
    class2 = MyClass(2)

Output (Python 3.7.x)

function1: 12

function2: 12

Answered By: Serjik

This is a simple answer, this will allow you to clear the screen for example. There are two examples below, with eval and exec, that will print 0 at the top after cleaning (if you’re using Windows, change clear to cls, Linux and Mac users leave as is for example) or just execute it, respectively.

Answered By: Number File

getattr calls method by name from an object.
But this object should be parent of calling class.
The parent class can be got by super(self.__class__, self)

class Base:
    def call_base(func):
        """This does not work"""
        def new_func(self, *args, **kwargs):
            name = func.__name__
            getattr(super(self.__class__, self), name)(*args, **kwargs)
        return new_func

    def f(self, *args):
        print(f"BASE method invoked.")

    def g(self, *args):
        print(f"BASE method invoked.")

class Inherit(Base):
    def f(self, *args):
        """function body will be ignored by the decorator."""

    def g(self, *args):
        """function body will be ignored by the decorator."""

Inherit().f() # The goal is to print "BASE method invoked."
Answered By: 정도유

Although getattr() is elegant (and about 7x faster) method, you can get return value from the function (local, class method, module) with eval as elegant as x = eval('')(). And when you implement some error handling then quite securely (the same principle can be used for getattr). Example with module import and class:

# import module, call module function, pass parameters and print retured value with eval():
import random
bar = 'random.randint'
randint = eval(bar)(0,100)
print(randint) # will print random int from <0;100)

# also class method returning (or not) value(s) can be used with eval: 
class Say:
    def say(something='nothing'):
        return something

bar = 'Say.say'
print(eval(bar)('nice to meet you too')) # will print 'nice to meet you' 

When module or class does not exist (typo or anything better) then NameError is raised. When function does not exist, then AttributeError is raised. This can be used to handle errors:

# try/except block can be used to catch both errors
    eval('')() # raises AttributeError because function does not exist
    eval('Says.say')() # raises NameError because the class does not exist
    # or the same with getattr:
    getattr(Say, 'talk')() # raises AttributeError
    getattr(Says, 'say')() # raises NameError
except AttributeError:
    # do domething or just...
    print('Function does not exist')
except NameError:
    # do domething or just...
    print('Module does not exist')
Answered By: Lukas

i’m facing the similar problem before, which is to convert a string to a function. but i can’t use eval() or ast.literal_eval(), because i don’t want to execute this code immediately.

e.g. i have a string "", and i want to assign it to x as a function name instead of a string, which means i can call the function by x() ON DEMAND.

here’s my code:

str_to_convert = ""
exec(f"x = {str_to_convert}")

as for your question, you only need to add your module name foo and . before {} as follows:

str_to_convert = "bar"
exec(f"x = foo.{str_to_convert}")

WARNING!!! either eval() or exec() is a dangerous method, you should confirm the safety.
WARNING!!! either eval() or exec() is a dangerous method, you should confirm the safety.
WARNING!!! either eval() or exec() is a dangerous method, you should confirm the safety.

Answered By: Bowen 404

In python3, you can use the __getattribute__ method. See following example with a list method name string:

func_name = 'reverse'

l = [1, 2, 3, 4]
>> [1, 2, 3, 4]

>> [4, 3, 2, 1]
Answered By: Aliakbar Ahmadi

Nobody mentioned operator.attrgetter yet:

>>> from operator import attrgetter
>>> l = [1, 2, 3]
>>> attrgetter('reverse')(l)()
>>> l
[3, 2, 1]
Answered By: U12-Forward

You means get the pointer to an inner function from a module

import foo
method =
executed = method(parameter)

This is not a better pythonic way indeed is possible for punctual cases

Answered By: Franz Kurt
Categories: questions Tags: , ,
Answers are sorted by their score. The answer accepted by the question owner as the best is marked with
at the top-right corner.