26.07.19 21:52, Bruce Leban пише:
On Fri, Jul 26, 2019 at 11:27 AM Serhiy Storchaka <[email protected]
<mailto:[email protected]>> wrote:
So you will be able to add errors handling like in:
with connect() as stream:
for data in stream:
try:
write(data)
except OSError:
handle_write_error()
except OSError:
handle_read_error()
except OSError:
handle_connection_error()
To put this in a simpler way: the proposal is to add an except clause
that applies ONLY to the direct operation of the with or for statement
and not to the block. That's an interesting idea.
The one thing I find confusing about your proposal is that the
proposed syntax does not imply the behavior. In a try statement, the
except appears at the end and after all possible statements that it
could cover. The proposal mimics that syntax but with different
semantics. Something like this would be much more clear what is going on:
for VARIABLE in EXPRESSION:
except EXCEPTION:
BLOCK
BLOCK
with EXPRESSION as VARIABLE:
except EXCEPTION:
BLOCK
BLOCK
while EXPRESSION:
except EXCEPTION:
BLOCK
BLOCK
Besides an unusual for Python layout (a clause has different indentation
than the initial clause of the statement to which it belongs) there is
other problem. The exception block is not the part of the "for" or
"with" block. After handling an exception in the "for" clause you do not
continue to execute the "for" block, but leave the loop. After handling
an exception in the "with" clause you do not continue to execute the
"with" block and do not call `__exit__` when leave it. To me, this
syntax is much more confusing than my initial proposition.
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