Why the colon?

Erv Young res04ft9 at gte.net
Sat Jun 29 01:33:31 CEST 2002


I've come a long way, baby!  Four days ago, I posted an inquiry on a MS 
Developer mailing list, to the following effect:  "How do I get MS Visual 
C++ 6.0 to act like good old non-visual, nonplussed (forgive me) plain old 
C?" and got back a response to the effect that I should forget C and use 
Perl.  And now here I am, having read the entire thread "Python vs. Perl: 
which one to learn?" and having identified the pieces of Python that I need 
for the job at hand.  I will omit several intermediate steps on the journey.

But I have a question.  Let me set it in the context of the first code 
snippet in section 4.7.1 
(http://www.python.org/doc/current/tut/node6.html#SECTION006710000000000000000) 
of the on-line tutorial

1. def ask_ok(prompt, retries=4, complaint='Yes or no, please!'):
2.     while 1:
3.         ok = raw_input(prompt)
4.         if ok in ('y', 'ye', 'yes'): return 1
5.         if ok in ('n', 'no', 'nop', 'nope'): return 0
6.         retries = retries - 1
7.         if retries < 0: raise IOError, 'refusenik user'
8.         print complaint

where I have added line numbers for the sake of the discussion.  I 
understand the colons in the middle of lines 4, 5, and 7 as statement 
separators.  Makes perfect sense.

Then what am I to make of the colons at the end of lines 1 and 
2?  "Yoo-hoo, interpreter!  I'm about to start indenting now!"  Hmmm....

Maybe one of you can help me understand this syntactic convention a little 
better.  An invitation to continue RTFM would be quite in order, if it were 
accompanied by a specific URL or section number.  (An invitation to read 
the whole thing like a novel would be a bit un-Python-like, as near as I 
can tell.)

Thanks.

--erv






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