using range() in for loops

[Alex Martelli]

Georg Brandl <g.brandl-nospam at gmx.net> wrote:

> Steven D'Aprano wrote:
> > On Wed, 05 Apr 2006 16:15:12 +0200, Georg Brandl wrote:
> > 
> >> sushant.sirsikar at gmail.com wrote:
> >>> hi John,
> >>>      Python doesn't provide for loop like C / C++ but using Range() or
> >>> Xrange() you can achive all the functionalities of the C for loop.
> >> 
> >> Not quite.
> > 
> > Care to explain what the differences are, or shall we guess?
> 
> C's for is much more powerful.
> 
> for(a; b; c) { d } translates to
> 
> a
> while b
>  d
>  c
> 
> which can't be replaced by a simple
> 
> for i in range(...)

No, but it can be easily replaced by:

# factoring out the loopstructure...
def gotcha():
    a
    while b:
        yield c

# ...from the loopbody
for i in gotcha():
    d

or several variations thereof.  In C++, I almost half-heartedly replace
most of Python's generators' power with C++'s templated iterators, but
when I program in C I find myself really straightjacketed these days in
NOT being able to pull out the "loopstructure" as I can in Python (and,
about halfway, in C++).


Alex