[issue2610] string representation of range

[Brad Miller]

New submission from Brad Miller <bonelake at gmail.com>:

I use Python in my CS1 and CS2 curriculum and I have a question.
As I've been using the Python 3.0 alphas one of the things that I am
bothered by is that I cannot see the sequence produced by range
without introducing students to the list() function.

I typically introduce range on day 1 of class and show students what
it produces without making a big deal out of the fact that it creates
a list.  They all accept this and things work out nicely when I
introduce lists for real in a week or two.

My question is why couldn't the __str__ method for the range object be
more friendly and show a representation of the sequence?  I understand
why __repr__ should return range(0,10) for an object created using
range(10) but couldn't print(range(10)) produce [0, 1, 2, ... 9]
The ... could even be used if the sequence were excessively long.

I have attached a patch, which follows the suggestion from Guido on how 
to format the string so it is not confused with a list.

This is my first attempt at patching any part of the C code for Python.  
Please let me know what should be changed and If I've missed something.

In particular I wonder whether I should be nesting any calls to PyNumber 
functions or whether temporary variables should be used to avoid leaking 
memory?

In addition I get the following warning on the line where I install the 
range_str function in the PyRange_Type array.

Objects/rangeobject.c:357: warning: initialization from incompatible 
pointer type


Brad

----------
components: Interpreter Core
files: range_str.patch
keywords: patch
messages: 65316
nosy: bmiller
severity: normal
status: open
title: string representation of range
type: feature request
versions: Python 3.0
Added file: http://bugs.python.org/file10000/range_str.patch

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