odd behavior

[Greg]

Forgive me, and be kind, as I am just a newby learning this language
out of M.L. Hetland's book. The following behavior of 2.4.1 seems very
strange

x = ['aardvark', 'abalone', 'acme', 'add', 'aerate'] x.sort(key=len)
x ['add', 'acme', 'aerate', 'abalone', 'aardvark'] x.sort(reverse=True)
x

['aerate', 'add', 'acme', 'abalone', 'aardvark']
The function called on line 4, at least to me, should work on x as it
was on line 3, not the previously existing x on line 1. What gives?
By the way these functions do not exist in 2.3.5 so they must be newly
implemented.

[Kristian Zoerhoff]

On 11 Nov 2005 11:34:47 -0800, Greg <gs*******@gmail.com> wrote:

Forgive me, and be kind, as I am just a newby learning this language
out of M.L. Hetland's book. The following behavior of 2.4.1 seems very
strange

x = ['aardvark', 'abalone', 'acme', 'add', 'aerate'] x.sort(key=len)
x ['add', 'acme', 'aerate', 'abalone', 'aardvark'] x.sort(reverse=True)
x ['aerate', 'add', 'acme', 'abalone', 'aardvark']
The function called on line 4, at least to me, should work on x as it
was on line 3, not the previously existing x on line 1. What gives?

The key option defaults to an alphabetic sort *every time* you call
sort, so if you want to change this, you must call for your sort key
each time. To do what you want, roll the sorts into one step:

x.sort(key=len, reverse=True)
x

['aardvark', 'abalone', 'aerate', 'acme', 'add']
--
Kristian

kristian.zoerhoff(AT)gmail.com
zoerhoff(AT)freeshell.org

[Lee Harr]

On 2005-11-11, Kristian Zoerhoff <kr***************@gmail.com> wrote:

On 11 Nov 2005 11:34:47 -0800, Greg <gs*******@gmail.com> wrote:

Forgive me, and be kind, as I am just a newby learning this language
out of M.L. Hetland's book. The following behavior of 2.4.1 seems very
strange

>>> x = ['aardvark', 'abalone', 'acme', 'add',

'aerate']

>>> x.sort(key=len)
>>> x

['add', 'acme', 'aerate', 'abalone', 'aardvark']

>>> x.sort(reverse=True)
>>> x

['aerate', 'add', 'acme', 'abalone', 'aardvark']
The function called on line 4, at least to me, should work on x as it
was on line 3, not the previously existing x on line 1. What gives?

The key option defaults to an alphabetic sort *every time* you call
sort, so if you want to change this, you must call for your sort key
each time. To do what you want, roll the sorts into one step:

x.sort(key=len, reverse=True)
x ['aardvark', 'abalone', 'aerate', 'acme', 'add']

.... or just reverse it after:

x.sort(key=len)
x.reverse()
x

['aardvark', 'abalone', 'aerate', 'acme', 'add']

[Steven D'Aprano]

On Fri, 11 Nov 2005 11:34:47 -0800, Greg wrote:

Forgive me, and be kind, as I am just a newby learning this language
out of M.L. Hetland's book. The following behavior of 2.4.1 seems very
strange

x = ['aardvark', 'abalone', 'acme', 'add', 'aerate']
x.sort(key=len)
x ['add', 'acme', 'aerate', 'abalone', 'aardvark'] x.sort(reverse=True)
x

['aerate', 'add', 'acme', 'abalone', 'aardvark']

The function called on line 4, at least to me, should work on x as it
was on line 3, not the previously existing x on line 1. What gives?

Why do you think it isn't operating on x as it is? The second sort is
sorting in reverse lexicographic order, which is the result you get.

I'm not running Python 2.4 so I can't test this, but to get the result you
want I guess you want this:

py> x.sort(key=len, reverse=True)
py> x
['aardvark', 'abalone', 'aerate', 'acme', 'add']

or:

py> x.sort(key=len)
py> x.reverse()
--
Steven.