in which of the two holes should go a cockroach in this case?

+----1+
|D    2
|     |
+-----+
   ↓
+----1+
|    U2
|     |
+-----+

Teaches assertions in regular expressions. Must be approved. Nice kata

and how long?)

The solution is wrong. It find position of braces and use weakness of testing. Mistaken for simple examples: [1, '['], ['[', 1] you program returns False, or [(1), 1], [1, (1)] returns True

sorry

you actually change input matrix, so test case change itself. If you don't want to change the code you must find the way to copy all contain of the matrix(may be tricky)

sorry for asking. in the solutions above, where the split method is used twice in a line, does it affect performance in general, or are the list cached?

Not in general, but coz autor make 'k' less or equal than length of sequence, it is work

Tests and solution have been resolved for repeated values.

did the same🙂. One note: many functions automatically polls the generator, so it senseless to go through the list twice.

''.join([x for x in iter]) = ''.join(x for x in iter)
   max([x for x in iter]) = max(x for x in iter)

etc

Thanks for the translation!

OOP was added as an exercise. Tests fixed. Added case pipe = []

Sorry, but this case is just trivial, I'll add it to random tests