While this looks attractive to me, and it's definitely better to change statement and comprehension syntax at the same time, this makes the comprehension ambiguous to human parsing.
[f(x) for x in list if x > 10] basically can be read as
for x in list:
if x > 10:
f(x)
This kind of interpretation becomes critical if you nest more than two levels. But [f(x) for x in list while x < 10] could read either as
for x in list while x < 10:
f(x)
which is how you want it to be read, or (more in line with earlier list comp habits):
for x in list:
while x < 10:
f(x)
which would be totally wrong.
I don't think this is a very serious problem (certainly not for the interpreter), but it's a stumbling block.
On Mon, Jul 1, 2013 at 10:03 PM, Jan Kaliszewski
<zuo@chopin.edu.pl> wrote:
2013-07-02 00:44, Oscar Benjamin wrote:
[...]
Having a while clause on for loops is not just good because it saves a
couple of lines but because it clearly separates the flow control from
the body of the loop (another reason I dislike 'break if'). In other
words I find the flow of the loop
for p in primes() while p < 100:
print(p)
easier to understand (immediately) than
for p in primes():
if p >= 100:
break
print(p)
+1
Cheers.
*j