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user2224350
user2224350

Reputation: 2334

Mutually excluding arguments in Python

What's the best way to define a function that depends on mutually excluding arguments, i.e. set of arguments where I only need to specify one at a time. A simple example would be a function that takes a physical parameter as the input, say the frequency. Now I want the user to be able to specify the frequency directly or the wavelength instead, so that they could equally call

func(freq=10)
func(wavelen=1).

One option would be kwargs, but is there a better way (regarding docstrings for example)?

Upvotes: 0

Views: 204

Answers (2)

OnY
OnY

Reputation: 897

Assuming all possible argument names are known, how about using a default of None?

def func(freq=None, wavelen=None):
   if freq:
       print(freq)
   elif wavelen:
       print(wavelen)

Using elif you can prioritize which argument is more important and considered first. You can also write code to return error if more than one argument is given, using xor:

def func(freq=None, wavelen=None):
   if not(freq ^ wavelen):
       raise Exception("More than one argument was passed")
   if freq:
       print(freq)
   elif wavelen:
       print(wavelen)

Upvotes: 1

Alain T.
Alain T.

Reputation: 42133

Since the calculations are going to be different, why not make that part of the function name and have two distinct functions (rather than a bunch of ifs):

def funcWavelen(w):
    ...

def funcFreq(f):
    ...

Upvotes: 0

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