Call a Python Method by Name

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

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.

Call a Python method by name

Use the built-in getattr() function:

class Foo:
    def bar1(self):
        print(1)
    def bar2(self):
        print(2)

def call_method(o, name):
    return getattr(o, name)()

f = Foo()
call_method(f, "bar1")  # prints 1

You can also use setattr() for setting class attributes by names.

How to get the caller's method name in the called method?

inspect.getframeinfo and other related functions in inspect can help:

>>> import inspect
>>> def f1(): f2()
... 
>>> def f2():
...   curframe = inspect.currentframe()
...   calframe = inspect.getouterframes(curframe, 2)
...   print('caller name:', calframe[1][3])
... 
>>> f1()
caller name: f1

this introspection is intended to help debugging and development; it's not advisable to rely on it for production-functionality purposes.

Python: call a function from string name

If it's in a class, you can use getattr:

class MyClass(object):
    def install(self):
          print "In install"

method_name = 'install' # set by the command line options
my_cls = MyClass()

method = None
try:
    method = getattr(my_cls, method_name)
except AttributeError:
    raise NotImplementedError("Class `{}` does not implement `{}`".format(my_cls.__class__.__name__, method_name))

method()

or if it's a function:

def install():
       print "In install"

method_name = 'install' # set by the command line options
possibles = globals().copy()
possibles.update(locals())
method = possibles.get(method_name)
if not method:
     raise NotImplementedError("Method %s not implemented" % method_name)
method()

Call a function from a stored string in Python

You can do this :

eval(input("What function do you want to call? ") + '()')

I have a string whose content is a function name, how to refer to the corresponding function in Python?

Since you are taking user input, the safest way is to define exactly what is valid input:

dispatcher={'add':add}
w='add'
try:
    function=dispatcher[w]
except KeyError:
    raise ValueError('invalid input')

If you want to evaluate strings like 'add(3,4)', you could use safe eval:

eval('add(3,4)',{'__builtins__':None},dispatcher)

eval in general could be dangerous when applied to user input. The above is safer since __builtins__ is disabled and locals is restricted to dispatcher. Someone cleverer than I might be able to still cause trouble, but I couldn't tell you how to do it.

WARNING: Even eval(..., {'__builtins__':None}, dispatcher) is unsafe to be applied to user input. A malicious user could run arbitrary functions on your machine if given the opportunity to have his string evaluated by eval.

How to call a method whose name is stored in a variable

Create a dict of functions that you want to call using a string:

def test(test_config):
    for i in test_config:
      print i.header //prints func1
      print type(i.header)
      try:
        methods[i.header]()
      except (AttributeError, TypeError):
        logging.error("Method  %s not implemented"%(i.header)) 

def func1():
    print "In func1"
def func2():
    print "In func2"

methods = {u'func1':func1, u'func2':func2} #Methods that you want to call

Using class:

class A:
    def test(self, test_config):
        try:
          getattr(self, i.header)()
        except AttributeError:
           logging.error("Method  %s not implemented"%(i.header)) 

    def func1(self):
        print "In func1"
x = A()
x.test(pass_something_here)

How to call Python functions dynamically

If don't want to use globals, vars and don't want make a separate module and/or class to encapsulate functions you want to call dynamically, you can call them as the attributes of the current module:

import sys
...
getattr(sys.modules[__name__], "clean_%s" % fieldname)()

Determine function name from within that function (without using traceback)

Python doesn't have a feature to access the function or its name within the function itself. It has been proposed but rejected. If you don't want to play with the stack yourself, you should either use "bar" or bar.__name__ depending on context.

The given rejection notice is:

This PEP is rejected. It is not clear how it should be implemented or what the precise semantics should be in edge cases, and there aren't enough important use cases given. response has been lukewarm at best.

Using a string in function name during call in python

Create a dict of your functions and use it to dispatch using somevar:

class MyClass:
    def a1_suffix(self, option):
        return "does something"

    def a2_suffix(self, option):
        return "does something else"

    def myfunction(self, somevar, option):
        functions = {"a1": self.a1_suffix, "a2": self.a2_suffix}
        func = functions[somevar]
        return func(option)

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