Call a function from a stored string in Python

Question

What I need is something that gets the variable and if the variable is the name of a function, the function will be called. I am not trying to get a function from a module but from within the program itself

Example:

def foo():
    print("Foo")
callfunction = input("What function do you want to call? ")

callfunction() ## Not sure what to put here but but lets say callfunction is foo.

I don't want something like this because I have many functions:

if callfunction == "Foo"
    Foo()
else:
    print("No function with that name")

My question is something like this, but I ask for the Python syntax. I am using Python 3.5.1

Related: How can I select a variable by (string) name?

wjandrea
– wjandrea

2024-03-23 19:40:04 +00:00
Commented Mar 23, 2024 at 19:40 — wjandrea
– wjandrea, Commented Mar 23, 2024 at 19:40

Daniel Roseman · Accepted Answer · 2017-02-14 13:32:14Z

24

Use a dict mapping names to functions.

call_dict = {
    'foo': foo,
    'bar': bar
}
call_dict[callfunction]()

answered Feb 14, 2017 at 13:32

Daniel Roseman

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1 Comment

wjandrea Over a year ago

@drascom What do you mean? That code looks fine. Are the functions actually methods? Then it might get tricky.

Jarvis · Accepted Answer · 2017-02-14 13:45:44Z

7

You can do this :

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

edited Feb 14, 2017 at 13:45

answered Feb 14, 2017 at 13:38

Jarvis

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2 Comments

Duncan Over a year ago

This allows the persons using it to execute arbitrary python code (just so long as whatever they do ends with a callable). For example they might just choose to erase all your files.

Matthias Over a year ago

@KalkidanTadesseZewdieBeyene: At the first glance this might look like the easiest solution but it's a very very very dangerous solution. Read Eval really is dangerous.

Duncan · Accepted Answer · 2017-02-14 13:35:46Z

It is quite common in Python to use the command pattern. First move all of your functions into a class, and give them names which have a prefix that isn't used in the input. Then use getattr() to find the correct function and call it.

class Commands():
   def cmd_foo(self):
       print("Foo")

   def callFunction(self, name):
       fn = getattr(self, 'cmd_'+name, None)
       if fn is not None:
            fn()

This has a couple of advantages over Daniel's call_dict: you don't have to list the name of the functions a second time, and you don't have to list the callable functions a second time either.

The 'cmd_' prefix is there to ensure you can have other methods in the class but still control exactly which ones are directly callable.

Elmex80s · Accepted Answer · 2017-02-14 13:40:10Z

2

This should do it

import inspect
import your_module

list_of_functions = inspect.getmembers(your_module, inspect.isfunction)

Now list_of_functions is a list of tuples with the name of each function at position 0 and the function itself at position 1.

answered Feb 14, 2017 at 13:40

Elmex80s

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Comments

Ben Jeffrey · Accepted Answer · 2024-06-25 13:35:42Z

1

Very late to the game here, but if I understand the objective correctly I think you can use locals(), assuming that the functions you want to call are already imported or defined in the same module.

def foo():
    print("foo has been called")

call_function_name = input("What function do you want to call? ")

function_to_call = locals()[call_function_name] # can also use locals().get(call_function_name) if you want to be a bit more defensive
function_to_call()

answered Jun 25, 2024 at 13:35

Ben Jeffrey

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