On 7/10/2020 1:21 AM, Stefano Borini wrote:
Just my 2 cents, I find it kind of annoying that the whole structure requires two levels of indentation to actually reach the operational code. This would be a first in python.
I would prefer an option akin to if elif elif else where each block is only one level deep. Me too.
That would also sidestep the dilemma of whether else: (if implemented) should be indented like case: or like match: because they would be the same. match: t case ("rect", real, imag): return complex(real, imag) case ("polar", r, phi): return complex( r* cos(phi), r*sin(phi) else: return None but it does make the match: block not a statement group, which was disturbing to some. On the other hand, this has a correspondence to: try: throw expression except (type of expression) as exc1: blah blah1 except (another type) as exc2: blah blah2 else: blah blah3 In fact, one _could_ wrap this whole feature into the try: syntax... the match statement would be tried, and the cases would be special types of exception handlers: try: match expression case ("rect", real, imag): return complex(real, imag) case ("polar", r, phi): return complex( r* cos(phi), r*sin(phi) else: return None If the expression could fail to be calculated, one could have a mix of except clauses also to catch those, rather than needing to wrap the whole match expression in a separate try to handle that case [making the nesting even deeper :( ] There might even be a use for using case clauses to extend "normal" exception handling, where the exception object could be tested for its content as well as its class to have different handling. try: raise Exception("msg", 35, things) case Exception( x, "widgets"): blah blah 1 case Exception( x, "characters"): blah blah 2 else: blah blah 3 In this not-fully-thought-through scenario, maybe the keyword match isn't even needed: "raise expression" could do the job, or they could be aliases to signify intent. In other words, a match expression would always "fail". The only mismatch here is that it points out the difference between try-else and match-else: try-else is executed if there is no failure, but if match always fails, else would never be appropriate, and case _: would be. In any case, it does seem there is a strong correlation between match processing and try processing, that I didn't see during other discussions of the possible structural similarities. "match 3 / 0:" would clearly need to be wrapped in a try: try: match x / y: case 43: print("wow, it is 43") case 22: print("22 seemed less likely than 43 for some reason") case _: print("You get what you get") except ZeroDivisionError as exc: print(f"But sometimes you get an exception {exc}") or: try: raise x / y case 43: print("wow, it is 43") case 22: print("22 seemed less likely than 43 for some reason") case exc := ZeroDivisionError: print(f"But sometimes you get an exception: {exc}") case _: print("You get what you get")