Python dynamic function names

Question

I'm looking for a better way to call functions based on a variable in Python vs using if/else statements like below. Each status code has a corresponding function

if status == 'CONNECT':
 return connect(*args, **kwargs)
elif status == 'RAWFEED':
 return rawfeed(*args, **kwargs)
elif status == 'RAWCONFIG':
 return rawconfig(*args, **kwargs)
elif status == 'TESTFEED':
 return testfeed(*args, **kwargs)
...

I assume this will require some sort of factory function but unsure as to the syntax

Answer 1

you might find getattr useful, I guess

import module
getattr(module, status.lower())(*args, **kwargs)

• drjeep: Thanks for this example, I didn't realize getattr() also worked on modules

Answer 2

The canonical way to do this is to use a dictionary to emulate switch or if/elif. You will find several questions to similar problems here on SO.

Put your functions into a dictionary with your status codes as keys:

funcs = {
 'CONNECT': connect,
 'RAWFEED': rawfeed,
 'RAWCONFIG' : rawconfig,
 'TESTFEED': testfeed
}
funcs[status](*args, **kwargs)

• SilentGhost: funcs['status'] will raise KeyError
• Andrew T: I think it is a safe way, it raises an exception when status is an unexpected method name.
• S.Lott: DRY rarely applies in cases like this. The initial list of functions may have string-like names; but this often diverges into more complex relationships.
• vartec: @S.Lott: the question title states 'dynamic functions names'. This is static mapping.
• hasen: This is not the canonical pythonic way for function dispatching. getattr is the canonical method in this case

Answer 3

assuming that these functions belong to some module:

import module
return getattr(module, status.lower()).__call__(*args, **kwargs)

Answer 4

it seams that you can use getattr in a slightly different (in my opinion more elegant way)

import math
getattr(math, 'sin')(1)

or if function is imported like below

from math import sin

sin is now in namespace so you can call it by

vars()['sin'](1)

Answer 5

Some improvement to SilentGhost's answer:

globals()[status.lower()](*args, **kwargs)

if you want to call the function defined in the current module.

Though it looks ugly. I'd use the solution with dictionary.

Answer 6

Look at this: getattra as a function dispatcher

• Drachenfels: Link is dead, decrementing score. Sorry for that.

Answer 7

I encountered the same problem previously. Have a look at this question, I think its what you are looking for.

Dictionary or If Statements

Hope this is helpful

Eef

Answer 8

some change from previous one:

funcs = {
'CONNECT': connect,
'RAWFEED': rawfeed,
'RAWCONFIG' : rawconfig,
'TESTFEED': testfeed
}
func = funcs.get('status')
if func:
 func(*args, **kwargs)

• SilentGhost: no it doesn't. it's the same error that heikogerlach had in the beginning.
• drjeep: I replaced 'status' with the variable, so I suppose technically it doesn't. I'm more interested in the method than semantics