On 2020-04-10 5:21 p.m., Elliott Dehnbostel wrote:
Hello Everyone,
If I've done this incorrectly, please let me know so that I can
improve/revise. I'm new to the Python community and quite enjoy the
more functional features of Python 3, but have I have a peeve about
it. I'd like to propose and discuss the following enhancement to Python 3:
*
Consider the following trivial for-loop:*
chars= "abcaaabkjzhbjacvb"
seek= {'a','b','c'}
count= 0
for ain chars:
if ain seek:
count+= 1
Gross. Twice nested for a simple count.
/We could refactor the block like so:/
chars= "abcaaabkjzhbjacvb"
seek= {'a','b','c'}
count= 0
for ain filter(lambda c: cin seek, chars): count+= 1
Which is all well and good, but doesn't quite read like English. It's
verbose, too.
It also uses advanced concepts new programmers may not understand.
/We could do this:/
chars= "abcaaabkjzhbjacvb"
seek= {'a','b','c'}
count= sum([1 for ain charsif ain seek])
However, this changes important semantics by creating an entire new
list before summing.
Also, adding just one more expression to the most nested block thwarts
that refactor.
I propose the following enhancement:
chars= "abcaaabkjzhbjacvb"
seek= {'a','b','c'}
count= 0
for ain charsif ain seek: count+= 1
fwiw you got pretty close to these there:
sum(1 for a in chars if a in seek) # is valid
for a in (a for a in chars if a in seek): count += 1 # is also valid
(but ugly)
*What happened there?*
I've allowed a condition to follow the "for" construct without a colon
or newline between.
/To be clear, this remains incorrect:/
chars = "abcaaabkjzhbjacvb" seek = {'a','b','c'} count = 0 for a in
chars # No colon prior to the newlineifa inseek:count +=1
*Value proposal:*
I assert that the inlined 'if' condition pattern is superior to the
alternative refactors.
Right now, the way to acquire an invariant in a more nasty loop would be:
for ain iterable:
if condition:
continue
But this is messy and not particularly Pythonic.
The filter approach uses concepts that should not be necessary for
this task.
The comprehension approach has different, undesirable semantics.
*Conclusion:*
I wanted to submit my thoughts here before getting too deep into this.
Any input would be appreciated!
Thanks everyone.
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