empty clause of for loops

Wed Mar 16 20:27:44 EDT 2016

On 2016年3月17日 05:05 am, Sven R. Kunze wrote:
> What I don't understand is why Python features "if break, then no else
> clause", but "if empty, then empty clause".
>> I found this excellent post:
> https://shahriar.svbtle.com/pythons-else-clause-in-loops

That post describes the motivating use-case for the introduction
of "if...else", and why break skips the "else" clause:
for x in data:
 if meets_condition(x):
 break
else:
 # raise error or do additional processing 
It might help to realise that the "else" clause is misnamed. It should be
called "then":
for x in data:
 block
then:
 block
The "then" (actually "else") block is executed *after* the for-loop, unless
you jump out of that chunk of code by raising an exception, calling return,
or break.
As a beginner, it took me years of misunderstanding before I finally
understood for...else and while...else, because I kept coming back to the
thought that the else block was executed if the for/while block *didn't*
execute. I couldn't get code with for...else to work right and I didn't
understand why until finally the penny dropped and realised that "else"
should be called "then".
-- 
Steven