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On 5-Feb-09, at 3:37 PM, Chris Rebert wrote:
On Thu, Feb 5, 2009 at 8:05 AM, Riobard Zhan firstname.lastname@example.org
On 5-Feb-09, at 12:37 AM, Ben Finney wrote: >
Because indentation also occurs for other reasons, a major example being continuations of previous lines.
for line in foo: do_something( spam, line)
That's three lines at differing indentation levels, but two statements.
I find that the line-end colon is a strong visual indicator that a
suite is being introduced, as contrasted with some other
difference in indentation.
Actually this is the first concrete example for colons. Thanks very
much for bringing it up, Ben! :)
Here is a counter-example for the strong visual indicator cause.
for some_list in some_collection: do_something(some_list[1: ], something_else)
True; however, the parentheses and brackets are unbalanced and that
immediately stands out, at least for me, so I see something odd is
going on right away.
You do have to admit that example is a bit contrived though. Move the
], back onto the previous line and the code becomes perfectly clear.
Do you notice immediately that the left ( is unbalanced in your
original example? :P I see it odd right away, too.
Line continuations are not good examples to demonstrate the necessity
of colons, because soon you will run into the problem of requiring
semicolons at the end of every statement. I think Denis made it quite
clear in a previous reply.
do(some(), some_other(), some_more(complex=(True,)),
and_final_call(egg=(1,2,3,zzzzz=False))); # endof
statement is obvious (if semicolons are required)
I would also defend colons on the grounds that they let particularly short statements be one-liners:
def add(x,y): return x+y
# this one especially comes up a lot in practice
if x is None: x=42
for i in alist: print(i)
with the added bonus that you're forced to indent if the body becomes multiline (unless you use semicolons that is, in which case you're destined to burn in the Nth circle of Hell for your sin against the BDFL (blessed be his holiness) ;-P).
I think in my original proposal I stated it very clear the colons are
OPTIONAL and can be used for one-liners, just like semicolons. I did
not propose to eliminate colons all together.