How to invoke a function on an object dynamically by name?

Question

In Python, say I have a string that contains the name of a class function that I know a particular object will have, how can I invoke it?

That is:

obj = MyClass() # this class has a method doStuff()
func = "doStuff"
# how to call obj.doStuff() using the func variable?

I'm curious about why you would need to do this. This sounds like you may be doing something the hard way. Could you elaborate on your situation? — JoshD, Oct 17 '10 at 03:06
I have a cli app where I want to accept commands from the command line, but don't want to do something like: "if command = 'doThing' then obj.doThing() elseif command = 'someOtherThing' ... and so on. I want to add methods to the handler class and then they'd automatically be available on the cli — Roy Tang, Oct 17 '10 at 05:07
is that alright to do that? what situations would this approach not a good idea? i'm in a similar situation too, but i'm not sure if i'll go this way. somehow, i feel that it would be more clearer if i explicitly use branching instead. what do you think? thanks! — ultrajohn, Sep 03 '12 at 11:59

score 105 · Accepted Answer · edited Nov 05 '21 at 01:57

105

Use the getattr built-in function. See the documentation

obj = MyClass()
try:
    func = getattr(obj, "dostuff")
    func()
except AttributeError:
    print("dostuff not found")

edited Nov 05 '21 at 01:57

Henry Ecker

answered Oct 17 '10 at 03:05

Adam Vandenberg

2

This link is also having a useful and an important example of the above question https://gist.github.com/hygull/41f94e64b84f96fa01d04567e27eb46b – hygull Dec 31 '17 at 01:56
Works well for a call but didn't find the way for assigning a value to the method. Eg: `obj."dostuff" = x` – Abpostman1 Apr 28 '22 at 13:29
Answering to myself : Didn't know either SETATTR. So `func = setattr(obj, "dostuff", x)` will do the job – Abpostman1 Apr 28 '22 at 13:40

1 Answers1