Python naming convention for variables that are functions

Question

Does Python have a naming convention for variables that are functions? I couldn't see anything specific for this in PEP-8 (other than naming variables).

Since functions are first-class objects in Python, is using a _fn suffix, or something similar, a recognized convention?

EDIT: Updated with more realistic example

Example:

def foo_a():
    print 'a'

def foo_b():
    print 'b'

funcs = {'a': foo_a, 'b': foo_b}

# dynamically select function based on some key
key = 'a'
foo_fn = funcs[key]

Answer 1

Does Python have a naming convention for variables that are functions?

No it does not, functions are first class objects in Python. Pass the function name as you would access it for calling.

For example:

def foo():
    pass

foo() # calling

another_function(foo) # passing foo

One of the hardest things in programming is getting naming right, however. I would certainly use a more descriptive name, probably one that is a verb. For example:

def do_nothing():
    pass

EDIT: Same deal, but there's nothing to stop you from using _fn as a suffix if it makes your code clearer:

def foo_a():
    print 'a'

def foo_b():
    print 'b'

funcs = {'a': foo_a, 'b': foo_b}

# dynamically select function based on some key
key = 'a'
foo_fn = funcs[key]

foo_fn() # calling
another_function(foo_fn) # passing

Answer 2

Functions are only a subset of what in Python are callable objects. callable is just an object type, such as are str, list or dict. There is no convention for naming any of them and I, particularly, don't see a reason to why this would be any different with callable.