Is current integer for-loop syntax a wart?

[Michael Chermside]

> PEP 276 (Simple Iterator for ints) and PEP 284 (Integer for-loops), among
> others, are written from the perspective that the current integer for-loop
> syntax
> 
>     for i in range(10):
> 
> is a wart.  Is this true?  That is, where does the Python community stand on
> this issue?

I think it's a wart.

Actually, I have only two complaints. The first is a minor, almost 
conceptual point... just because I want to loop from 0 to 9 doesn't mean 
I should have to allocate memory for the list [0,1,2,3,4,5,6,7,8,9]. The 
objection is more meaningful for longer loops. Of course, it's not a 
very strong objection, because I have options like:
               for i in xrange(10):
... but if I'm a beginner I might not know about that. And sometimes 
using range() is faster than using xrange() (I'm not clear on why). But 
this is really NOT an important objection and the more I consider it the 
less I care.


The second complain is significant (I think). That is the following:
        for i in range(len(mySequence)):
This is something that I use all the time, and more relevently it is 
something that BEGINNERS use all the time. I want Python to be REALLY 
easy for beginners. I argue all the time that Python is better than Java 
even on pure syntax. In java you have to do this all the time:
     Iterator i = myCollection.iterator();
     while( i.hasNext() ) {
         MyClass x = (MyClass) i.next();
         <code using x>
     }
In python, that's as easy as this:
     for x in myCollection:
         <code using x>
or sometimes even this:
     [<code using x> for x in myCollection]
This is a real win for Python... having to type all that boilerplate 
every time I want to go through a list is painful... having syntax which 
makes COMMON things EASY, and UNUSUAL things EXPLICIT is a very 
important feature of Python.

Well, in my opinion, having to write
     for i in range(len(myList)):
begins to smack of too much boilerplate. Frankly, I'd be satisfied with 
option 2 from PEP 212 http://python.sourceforge.net/peps/pep-0212.html), 
making it as simple as:
     for i in indices(myList):
Or I'd be satisfied with PEP 276 
(http://python.sourceforge.net/peps/pep-0276.html), although the fact 
that it would affect contexs other than loops makes me somewhat queasy.

----

It has been suggested that the awkwardness in using range() or xrange() 
for loops which are not half-open, or which have a step size other than 
1 is a problem in need of a solution. I say "Wart?" -- ie, I've never 
found it to be a problem myself. If I get confused while writing it, I 
just find a way to be more explicit... often resorting to a "while" loop 
instead of "for". Never thought it was any big deal.

---

Finally, the BDFL has proposed that release 2.3 avoid introducing new 
syntax. GREAT IDEA. While I do claim to see some warts, I wouldn't say 
that these are in any way a priority! Let's go for solidity first, and 
language design second... because the language design is already excellent!

-- Michael Chermside



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