sort() doesn't work on dist.keys() ?

Re: sort() doesn't work on dist.keys() ?


"Steve Pinard" <[email protected] kwell.com> wrote in message
news:6cd58b6.03 07101214.34e99f [email protected] le.com...[color=blue]
> (Got a comm error trying to post first time, sorry if this
> is a duplicate)
>
> New to Python, so please bear with me.
>[color=green][color=darkred]
> >>> import sys
> >>> print sys.modules.key s() # works fine[/color][/color]
> ['code', ...snip... ][color=green][color=darkred]
> >>> print sys.modules.key s().sort() # returns None, why?[/color][/color]
> None
>
> According to my reference (Nutshell), keys() returns a
> "copy" of the dict keys as a list, so I would expect when
> I aply sort() to that list, I would get an in-place sorted
> version of that list. Why do I get None?
>
> TIA,
> - Steve
>[/color]

You said it yourself. It's an IN PLACE sort, so it won't return anything
(well, None, but that doesn't count). Try this:

**UNTESTED**[color=blue][color=green][color=darkred]
>>> mykeys = sys.modules.key s()
>>> print mykeys[/color][/color][/color]
[...a list of keys...][color=blue][color=green][color=darkred]
>>> mykeys.sort() #Note it's IN PLACE. Nothing is returned, so there's no[/color][/color][/color]
need to assign anything[color=blue][color=green][color=darkred]
>>> print mykeys[/color][/color][/color]
[...a SORTED list of keys...]

Greg

Re: sort() doesn't work on dist.keys() ?

In article <6cd58b6.030710 1214.34e99f2a@p osting.google.c om>, Steve Pinard wrote:[color=blue]
> (Got a comm error trying to post first time, sorry if this
> is a duplicate)
>
> New to Python, so please bear with me.
>[color=green][color=darkred]
>>>> import sys
>>>> print sys.modules.key s() # works fine[/color][/color]
> ['code', ...snip... ][color=green][color=darkred]
>>>> print sys.modules.key s().sort() # returns None, why?[/color][/color]
> None
>
> According to my reference (Nutshell), keys() returns a
> "copy" of the dict keys as a list, so I would expect when
> I aply sort() to that list, I would get an in-place sorted
> version of that list. Why do I get None?[/color]

From the documentation of the mutable sequence sort() method, note (7):

"The sort() and reverse() methods modify the list in place for
economy of space when sorting or reversing a large list. To remind
you that they operate by side effect, they don't return the sorted
or reversed list."

Or, in other words, sort() always returns None. If you want to sort, you
need to bind a name to the list you want to sort, first, then call sort() on
it and then print the now sorted list. For example:

sys_keys = sys.modules.key s()
sys_keys.sort()
print sys_keys

Hope this helps,

Troels Therkelsen

Re: sort() doesn't work on dist.keys() ?


"Steve Pinard" <[email protected] kwell.com> wrote in message
news:6cd58b6.03 07101214.34e99f [email protected] le.com...[color=blue]
> I would expect when
> I aply sort() to that list, I would get an in-place sorted
> version of that list. Why do I get None?[/color]

Apparently, you get None to remind you that you've done an inplace sort,

see

Re: sort() doesn't work on dist.keys() ?

On Thu, 2003-07-10 at 13:14, Steve Pinard wrote:[color=blue]
> (Got a comm error trying to post first time, sorry if this
> is a duplicate)
>
> New to Python, so please bear with me.
>[color=green][color=darkred]
> >>> import sys
> >>> print sys.modules.key s() # works fine[/color][/color]
> ['code', ...snip... ][color=green][color=darkred]
> >>> print sys.modules.key s().sort() # returns None, why?[/color][/color]
> None
>
> According to my reference (Nutshell), keys() returns a
> "copy" of the dict keys as a list, so I would expect when
> I aply sort() to that list, I would get an in-place sorted
> version of that list. Why do I get None?[/color]

Because sort() sorts the list in-place. It doesn't return anything
(which in Python means it returns None).

Try this instead:

keys = sys.modules.key s()
keys.sort()
print keys

--
Cliff Wells, Software Engineer
Logiplex Corporation (www.logiplex.net)
(503) 978-6726 (800) 735-0555

Re: sort() doesn't work on dist.keys() ?

Because sorts works in place and the sort fuction returns None rather than a
copy of the list. Try


import sys
temp = sys.modules.key s()
temp.sort()
print temp


Greg


Steve Pinard wrote:
[color=blue]
> (Got a comm error trying to post first time, sorry if this
> is a duplicate)
>
> New to Python, so please bear with me.
>[color=green][color=darkred]
>>>> import sys
>>>> print sys.modules.key s() # works fine[/color][/color]
> ['code', ...snip... ][color=green][color=darkred]
>>>> print sys.modules.key s().sort() # returns None, why?[/color][/color]
> None
>
> According to my reference (Nutshell), keys() returns a
> "copy" of the dict keys as a list, so I would expect when
> I aply sort() to that list, I would get an in-place sorted
> version of that list. Why do I get None?
>
> TIA,
> - Steve[/color]