Question

This is similar to method overloading. When print Hello(1, 2, 3) gets executed it returns "a and b" whereas I want it to return "a and b and c". I know I could have said if (a and b and c is None) then it would have worked. But if I had 20 parameter and I have to handle every case it would be just multiple if statements which I don’t think should be necessary. Is there a better way I should be doing such a problem?

 def Hello(a=None, b=None, c=None):
    if(a and b):
        return "a and b"
    if(a and c):
       return "a and c"
    if(a and b and c):
       return "a and b and c"

print Hello(1, 2, 3)

Answer 1

You need to rethink your program logic, really. Usually, an API will not have all-optional parameters where you need to build a large decision tree from all the inputs.

In other words, in a real program you won’t normally encounter a function where the behaviour is completely different for each of the different combinations of inputs. Invariably, the legal combinations is much, much smaller even for a larger number of optional parameters.

For your toy example, you can come up with other ways to create your return value not involving a decision tree:

• map responses:

  responsemap = {
      (True,  True,  False): "a and b",
      (True,  False, True):  "a and c",
      (True,  True,  True):  "a and b and c"
  }
  
  def Hello(a=None, b=None, c=None):
      return responsemap.get((bool(a), bool(b), bool(c)), None)
  

• build a string based on the inputs:

  def Hello(a=None, b=None, c=None):
      return ' and '.join([n for n in ('a', 'b', 'c') if locals()[n]])