combination of eval + f-strings + match-case

Question

How do I make the following work,

for i in ['int', 'bool']:
  x = eval(f'match 1: \
               case {i}(): print(1)')

that is I want to run a match-case f-string inside an eval.

I am inspecting the match-case on the builtins. I was able to solve this problem, by using, `cc = compile(f'match 1:\n\tcase {i}(): print(1)','','single') y = eval(cc)` — apostofes, Jun 14 '22 at 04:39
But surely in that case they can't return `1`? `int()` will return `0` and `bool()` will return `False` — Nick, Jun 14 '22 at 06:14
case is like a type check, it does not evaluate, so, `int()` would just check whether `1` is an integer (and print `1`), and `bool()` will just check whether `1` is a bool (and print nothing). it does not evaluate `int()` to `0` or `bool()` to `False` — apostofes, Jun 14 '22 at 06:22
Ah yeah, I forgot about matching against classes... juggling too many languages in my head... — Nick, Jun 14 '22 at 06:29

Tranbi · Answer 1 · 2022-06-14T09:12:05.003

1

eval only evaluates Python expressions. match is a statement. So you should use exec:

for i in ['int', 'bool']:
  exec(f'match 1:\n \
  case {i}(): print(1)')

(also beware of line breaks/indents inside f-strings)

edited Jun 14 '22 at 09:12

answered Jun 14 '22 at 08:46

Tranbi

1 Answers1