Question

I have a function that expects to operate on a numeric type. I am reading the numbers to operate on from a file, so when I read them they are strings, not numeric. Is it better to make my function tolerant of other types (option (A) below), or convert to a numeric before calling the function (option (B) below)?

# Option (A)
def numeric_operation(arg):
    i = int(arg)
    # do something numeric with i

# Option (B)
def numeric_operation(arg):
    # expect caller to call numeric_operation(int(arg))
    # do something numeric with arg

Answer 1

If your function expects to operate on numeric data, then you are probably best off allowing Python to throw a TypeError if it doesn’t receive one and something goes wrong. I would say, do the conversion outside and handle the exception.

def numeric_operation(arg):
   # Do numeric things

try: 
  numeric_operation("abc")
except TypeError:
  print("That was supposed to be numeric.")