Python function pointer with different arguments

Question

I have defined three functions.

def evaluate1(a, b):
 pass

def evaluate2(a, b):
 pass

def evaluate3(a, b, c):
 pass

What I want to do use a pointer to record which evaluate function I will use depending on the test inputs. The logic is as shown follows:

def test(a, b, c, d):
 # let evaluate_function records which evaluate function I will use
 if c > 1:
 evaluate_function = evaluate3 # not sure
 else:
 if d:
 evaluate_function = evaluate1
 else:
 evaluate_function = evaluate2
 # execute the evaluate function
 evaluate_function(a, b, ?)

However, since evaluate3 has different arguments from evaluate1 and evaluate3. How should I do? Thanks!

• Ja8zyjits: use **kwargs that will help you with dynamic signatures.
• jonrsharpe: Must they have different arguments? If yes, could you use e.g. functools.partial or a lambda to wrap the one that takes three arguments such that the resulting evaluate_function always takes two arguments? If no, it would be easier if they didn't.
• hpaulj: Use *args in the definitions
• waynelpu: You can use default param in function declaration in c of evaluate3 if it can
• Nishant: Is the code in all three functions different?

Answer 1

You have come up with a good idea of using a 'function pointer' to select the function. But since you know which function you are selecting at the time, you could also bind up the params:

def test(a, b, c, d):
 # let evaluate_function records which evaluate function I will use
 if c > 1:
 evaluate_function = evaluate3 # not sure
 params = a,b,d
 else:
 if d:
 evaluate_function = evaluate1
 params = a,b
 else:
 evaluate_function = evaluate2
 params = a,c
 # execute the evaluate function
 evaluate_function(*params)

I'll leave it to you to properly select the params.

Answer 2

Why not just call the evaluate functions directly instead of assigning them to a function as so. Makes it more readable

def evaluate1(a, b):
 print('evaluate1')
def evaluate2(a, b):
 print('evaluate2')
def evaluate3(a, b, c):
 print('evaluate3')
def test(a, b, c=None, d=None):
 # let evaluate_function records which evaluate function I will use
 if c and c > 1:
 evaluate3(a, b, c)
 else:
 if d:
 evaluate1(a, b)
 else:
 evaluate2(a, c)
test(1,2,c=0.1,d=1)
#evaluate1
test(1,2)
#evaluate2
test(1,2,3)
#evaluate3