Hi folks,

I have a few decades of experience with software engineering using
assembler, C, FORTRAN, Pascal, Ada and a fair number of other languages.
I've been using Python as well for a number of years now.

Both Pascal and Ada have "end" statements, which make the code (at least
for me :-) ) a lot more readable and maintainable, especially if the
code within if/while/for statements gets longer and nested deeper. These
statements exist in these languages for a good reason.

I had a look in the archives to see if someone else already proposed
this but couldn't find anything, so here goes.

Please let me know whether you think this idea is worth to convert to a PEP.

thanks,
Jan


Idea:

To include optional "end if", "end while", "end for" and "end <function
name>", "end <class name>" in the language. The Python interpreter would
test that any "end" matches with the correct corresponding statements
and have the correct indentation, in other words throw an error if you
would write "end if" where an "end while" should be. This will be a
great help preventing errors with procedural logic, that I now have to
painstakingly debug at runtime, especially after moving bits of code around.

Python editors would ideally highlight "if" and "end if" just like they
now highlight "if". By default different colors could be picked for "if"
and "end if", "while" and "end while" etc.

All this is completely optional of course, so it won't break any
existing code.

Advantages:
- better readability and maintainability
- help prevent procedural logic mistakes
- editors could use this for improved highlighting of code

Disadvantages:
- none :-) it's optional, just like the typing that was introduced in
Python 3


Code example:

def func (i: int, j: int, k: int) -> None:
     if (i == 3):
         while (i < 15):
             i += 1
             if (k == 8):
                 lots of other code (think a page or more)
                 lots of other code
         here is more code <- to which if or while does this belong?
         and a bit more

further code


The code could be rewritten like this:

def func (i: int, j: int, k: int) -> None:
     if (i == 3):
         while (i < 15):
             i += 1
             if (k == 8):
                 lots of other code (think a page or more)
                 lots of other code
             end if
         end while (writing "end if" would throw an error at parse time)
         here is more code
         and a bit more
     end if
end func

further code



Looking forward to your feedback!

regards,
Jan
NEW ZEALAND



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