pythonic way to convert variable to list

Question

I have a function whose input argument can either be an element or a list of elements. If this argument is a single element then I put it in a list so I can iterate over the

Answer 1

First, there is no general method that could tell a "single element" from "list of elements" since by definition list can be an element of another list.

I would say you need to define what kinds of data you might have, so that you might have:

• any descendant of list against anything else
  • Test with isinstance(input, list) (so your example is correct)
• any sequence type except strings (basestring in Python 2.x, str in Python 3.x)
  • Use sequence metaclass: isinstance(myvar, collections.Sequence) and not isinstance(myvar, str)
• some sequence type against known cases, like int, str, MyClass
  • Test with isinstance(input, (int, str, MyClass))
• any iterable except strings:
  • Test with

.

    try: 
        input = iter(input) if not isinstance(input, str) else [input]
    except TypeError:
        input = [input]