suggestion to small improvement of PEP 634 -- Structural Pattern Matching

[alhabshi3k]

Firstly, congratulation on PEP 634, I just want to suggest an enhancement for the "match" statement.

• When the matching against cases of pattern, there are some situations when there is no match.
• Using a cluster of "else" make it more readable compared with using a wildcard case.
• It's likewise in cases of the "if", "for", "try" statements, when conditions are not matching or when elements in a collection are not found, having the cluster of "else" in the above-mentioned statements make the code syntaxial readable to express what the Python program should.

For example , taken from PEP 636 , instead of :

match command.split():
 case ["go", direction] if direction in current_room.exits:
 current_room = current_room.neighbor(direction)
 case ["go", _]:
 print("Sorry, you can't go that way")

the programmer have express a possible situation as :

match command.split():
 case ["go", direction] if direction in current_room.exits:
 current_room = current_room.neighbor(direction)
 case ["go", _]:
 print("Sorry, you can't go that way")
 else : 
 print( f"Sorry, I don't understand what you mean by {command}.")

I hope you got my point.

[pxeger]

This is not the place to suggest modifications to the specification in PEPs. In this case, an else clause was already considered and rejected; specifically in PEP 634's precursor PEP 622:

Add an else clause

We decided not to add an else clause for several reasons.

• It is redundant, since we already have case _:
• There will forever be confusion about the indentation level of the else: -- should it align with the list of cases or with the match keyword?
• Completionist arguments like "every other statement has one" are false -- only those statements have an else clause where it adds new functionality.

link

In future, please go to python-ideas for changes to PEPs, but in this case you're likely to find it has been discussed in-depth and is unlikely to change, especially since PEP 634 was formally accepted.

[alhabshi3k]

noted. thanks for the reply and information.