[Edu-sig] Why colon?

[Guido van Rossum]

> What is the use of the colon in def and if?
> It only seems to signal, indent the next line,
> but if the next line is indented anyway, 
> what is the colon's purpose?
> 
> We have a semi-colon to put multiple statements 
> on a line, why not use that for a single-line if,
> 
> if x > 0 ; print "positive"
> else ; print "negative"
> 
> Then when we use multiple lines we still indent,
> 
> if x > 0
>     print "positive"
> else
>     print "negative"
> 
> It is a common error of new Python programmers 
> to leave out the colon after def, if and else,
> and I can't explain why the colon is needed.
> 
> Thanks,
> Jeff Sandys

This is a FAQ (but anyway, it's too late to change):

http://www.python.org/cgi-bin/faqw.py?query=colon&querytype=simple&casefold=yes&req=search

    The colon is required primarily to enhance readability (one of the
    results of the expirimental ABC language). Consider this:

    if a==b 

	print a

    versus 

    if a==b: 

	print a

    Notice how the second one is slightly easier to read. Notice
    further how a colon sets off the example in the second line of
    this FAQ answer; it's a standard usage in English. Finally, the
    colon makes it easier for editors with syntax highlighting.

--Guido van Rossum (home page: http://www.python.org/~guido/)