Do union types actually exist in python?

Question

Since python is dynamically typed, of course we can do something like this:

def f(x):
    return 2 if x else \"s\"

But is this the way pyth

Answer 1

Here are a couple of options to deal with use-cases where you need a tagged union/sum type in Python:

• Enum + Tuples

  from enum import Enum
  Token = Enum('Token', ['Number', 'Operator', 'Identifier', 'Space', 'Expression'])
  
  (Token.Number, 42)                            # int type
  (Token.Operator, '+')                         # str type 1
  (Token.Identifier, 'foo')                     # str type 2
  (Token.Space, )                               # no data
  (Token.Expression, 'lambda', 'x', 'x+x')      # multiple data
  

• isinstance

  if isinstance(token, int):
      # Number type
  if isinstance(token, str):
      # Identifier type
  

• sumtypes module

These approaches all have their various drawbacks, of course.