Need a strange sort method...

[Paul Rubin]

Re: Need a strange sort method...

"SpreadTooT hin" <bjobrien62@gma il.comwrites:

I have one extra 10 that I shouldn't...

>
I think my loop termination is incorrect...

It looks wrong to me; try your loop on range(20) and see what happens.

maybe I should just stop when my new series size is the same size as
the original?

You should make exactly 3 passes. You might also want to use
list.extend rather than adding lists. Finally, your function modifies
its input list (by sorting it), which generally is not nice unless the
caller expects it and wants it. You can save the caller some trouble
by making a sorted copy to work from.

[Gerard Flanagan]

Re: Need a strange sort method...


Gerard Flanagan wrote:

Gerard Flanagan wrote:

SpreadTooThin wrote:

I have a list and I need to do a custom sort on it...
>
for example:
a = [1,2,3,4,5,6,7,8 ,9,10] #Although not necessarily in order

1 4 7 10
2 5 8
3 6 9
>

from math import sqrt

for i in range(2,12):
seq = range(1,i)
numcols = int(sqrt(len(se q)))
print columnise(seq, numcols)

>
should be:
>
numcols = int(sqrt(len(se q) + 0.5)
>

Feck! Missing a fecking bracket:

numcols = int(sqrt(len(se q)) + 0.5)

[mensanator@aol.com]

Re: Need a strange sort method...


SpreadTooThin wrote:

SpreadTooThin wrote:

Simon Brunning wrote:

On 10/16/06, Simon Brunning <simon@brunning online.netwrote :
>>a = [1,2,3,4,5,6,7,8 ,9,10]
>>a.sort(key=la mbda item: (((item-1) %3), item))
>>a
[1, 4, 7, 10, 2, 5, 8, 3, 6, 9]
>
Re-reading the OP's post, perhaps sorting isn't what's required:
>
>a[::3] + a[1::3] + a[2::3]
[1, 4, 7, 10, 2, 5, 8, 3, 6, 9]
>
--
Cheers,
Simon B
simon@brunningo nline.net
http://www.brunningonline.net/simon/blog/

>

Ok so this is what I got.. but there is an odd side effect:

def reslice(series) :
series.sort()
i = 1
newseries = series[::3]
while(1):
c = series[i::3]
if len(c) >= 3:
newseries = newseries + c
else:
break
i = i + 1
return newseries

a = [2,1,4,3,6,5,8,7 ,10,9]
b = reslice(a)
print b

>>[1, 4, 7, 10, 2, 5, 8, 3, 6, 9, 4, 7, 10]

I have one extra 10 that I shouldn't...

Actually, you have an extra 4,7,10.

>
>
I think my loop termination is incorrect...
maybe I should just stop when my new series size is the same size as
the original?

You can do this automatically (and pass the size of the
desired sublist grouping also).

def strange(n,d):
""" n list to sort
d sublist length
"""
LoL = []
for i in xrange(d):
LoL.append(n[i::d])
print LoL
out = []
for i in LoL:
out.extend(i)
return out

a = [1,2,3,4,5,6,7,8 ,9,10]
b = [1,3,5,7,11,13,1 7,19,23,29]
c = [1,2,3,4,4,5,6,7 ,8,9,10]
d = [1,2]

print a
test = strange(a,3)
print test
print

print a
test = strange(a,4)
print test
print

print a
test = strange(a,5)
print test
print

print b
test = strange(b,3)
print test
print

print c
test = strange(c,3)
print test
print

print d
test = strange(d,5)
print test
print

## [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
## [[1, 4, 7, 10], [2, 5, 8], [3, 6, 9]]
## [1, 4, 7, 10, 2, 5, 8, 3, 6, 9]
##
## [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
## [[1, 5, 9], [2, 6, 10], [3, 7], [4, 8]]
## [1, 5, 9, 2, 6, 10, 3, 7, 4, 8]
##
## [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
## [[1, 6], [2, 7], [3, 8], [4, 9], [5, 10]]
## [1, 6, 2, 7, 3, 8, 4, 9, 5, 10]
##
## [1, 3, 5, 7, 11, 13, 17, 19, 23, 29]
## [[1, 7, 17, 29], [3, 11, 19], [5, 13, 23]]
## [1, 7, 17, 29, 3, 11, 19, 5, 13, 23]
##
## [1, 2, 3, 4, 4, 5, 6, 7, 8, 9, 10]
## [[1, 4, 6, 9], [2, 4, 7, 10], [3, 5, 8]]
## [1, 4, 6, 9, 2, 4, 7, 10, 3, 5, 8]
##
## [1, 2]
## [[1], [2], [], [], []]
## [1, 2]

[SpreadTooThin]

Re: Need a strange sort method...


Tim Chase wrote:

for example:
a = [1,2,3,4,5,6,7,8 ,9,10] #Although not necessarily in order

def cmp(i,j): #to be defined in this thread.

>
Well, if you're willing to give up doing it in a cmp() method,
you can do it as such:
>

>>a.sort()
>>chunk_size = 3
>>[a[i::chunk_size] for i in range(chunk_siz e)]

[[1, 4, 7, 10], [2, 5, 8], [3, 6, 9]]
>
If you need it in a flat list, rather than as a list of
chunk_size lists (which are handy for iterating over in many
cases), there are ways of obtaining it, such as the hackish
>

>>sum([a[i::chunk_size] for i in range(chunk_siz e)], [])

[1, 4, 7, 10, 2, 5, 8, 3, 6, 9]
>
There are likely good recipes for flattening a list. I just
happen not to have any at my fingertips.
>
I'm not sure it's possible to do in a cmp() method, given that it
requires apriori knowledge of the dataset (are the numbers
contiguous?). Unless, of course, you have such a list...
>
However, as a benefit, this method should work no matter what the
list contains, as long as they're comparable to each other for an
initial sorting:
>

>>a = [chr(ord('a') + i) for i in range(10)]
>># a.sort() if it were needed
>>a

['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j']

>>sum([a[i::chunk_size] for i in range(chunk_siz e)], [])

['a', 'd', 'g', 'j', 'b', 'e', 'h', 'c', 'f', 'i']
>
>
-tkc

Yes this is excellent...
Doh... How easy was that! :)
[a[i::chunk_size] for i in range(chunk_siz e)]

[Ron Adam]

Re: Need a strange sort method...

Neil Cerutti wrote:

On 2006-10-16, Tim Chase <python.list@ti m.thechases.com wrote:

>If you need it in a flat list, rather than as a list of
>chunk_size lists (which are handy for iterating over in many
>cases), there are ways of obtaining it, such as the hackish
>>

>>>>sum([a[i::chunk_size] for i in range(chunk_siz e)], [])

>[1, 4, 7, 10, 2, 5, 8, 3, 6, 9]
>>
>There are likely good recipes for flattening a list. I just
>happen not to have any at my fingertips.

>
Actually, there isn't a good recipe in Python for flattening a
list. They all come out tasting like Circus Peanuts (Turkish
Delight for you non-Yanks).
>

Here's two that I came up with. They are both very fast compared to anything
else I've seen. Maybe they won't taste so much like Peanuts. :-)


def flatten(L):
""" Flatten a list in place.
"""
i = 0
while i < len(L):
while type(L[i]) is list:
L[i:i+1] = L[i]
i += 1
return L

def sflatten(sequen ce):
""" Return a flattened sequence as a list.
"""
def iterinner(seq):
for s in seq:
if hasattr(s, '__iter__'):
for i in iterinner(s):
yield i
else:
yield s
return list(iterinner( sequence))

Cheers,
Ron Adam

[Ron Adam]

Re: Need a strange sort method...

Ron Adam wrote:

Neil Cerutti wrote:

>On 2006-10-16, Tim Chase <python.list@ti m.thechases.com wrote:

>>If you need it in a flat list, rather than as a list of
>>chunk_size lists (which are handy for iterating over in many
>>cases), there are ways of obtaining it, such as the hackish
>>>
>>>>>sum([a[i::chunk_size] for i in range(chunk_siz e)], [])
>>[1, 4, 7, 10, 2, 5, 8, 3, 6, 9]
>>>
>>There are likely good recipes for flattening a list. I just
>>happen not to have any at my fingertips.

>>
>Actually, there isn't a good recipe in Python for flattening a
>list. They all come out tasting like Circus Peanuts (Turkish
>Delight for you non-Yanks).
>>

>
>
Here's two that I came up with. They are both very fast compared to
anything else I've seen. Maybe they won't taste so much like Peanuts.
:-)
>
>
def flatten(L):
""" Flatten a list in place.
"""
i = 0
while i < len(L):
while type(L[i]) is list:
L[i:i+1] = L[i]
i += 1
return L
>
def sflatten(sequen ce):
""" Return a flattened sequence as a list.
"""
def iterinner(seq):
for s in seq:
if hasattr(s, '__iter__'):
for i in iterinner(s):
yield i
else:
yield s
return list(iterinner( sequence))

Woops, cut the wrong one... Replace sflatten above with the following.


def flattened(seq):
""" Return a flattened sequence as a list.
"""
def visit(a, x):
for i in x:
if not hasattr(i, '__iter__'):
a.append(i)
else:
visit(a, i)
a = []
visit(a, seq)
return a

>
Cheers,
Ron Adam