Question

I want to do something like that:

action = :default

if some_condition1:
    action = :do_something

if some_condition2:
    action = :do_other_thing

...

if action == :default:
   one_reaction()
elif action == :do_something:
   other_reaction()
...

What should I use to represent actions choice?

Variants that come to mind:

• Create enumeration

  class MyActions:
      DEFAULT=1
      SO_SOMETHING=2
      SO_OTHER_THING=3
  

  inconvenient, need to scroll to and fro and “register” new action choices.

• Use magic numbers. Not good.

• Use strings.

Answer 1

“Symbols” in Lisp can be thought of, conceptually, as interned strings.

action = 'default'

if some_condition1:
    action = 'do_something'

if some_condition2:
    action = 'do_other_thing'

...

if action == 'default':
   one_reaction()
elif action == 'do_something':
   other_reaction()
...

Whenever you would use a symbol in Lisp, Python would use a string. Lisp has to make a distinction because it is homoiconic, but since Python isn’t homoiconic, the distinction is unnecessary.

Alternatives

If you use numbers instead, then you lose REPL-ability. For example,

default = 1
do_something = 2
do_other_thing = 3

>>> x = default
>>> x
1 # is 1 default? I can't remember...

There are more sophisticated ways to do this, like creating special classes, but the small benefit is not worth the added complexity.