about list

[Shi Mu]

How to run a function to make [1,2,4] become [[1,2],1,4],[2,4]]?
Thanks!

[bonono]

try to describe what you want as it is not very obvious, and has syntax
error.

Shi Mu wrote:

How to run a function to make [1,2,4] become [[1,2],1,4],[2,4]]?
Thanks!

[bonono]

try to describe what you want as it is not very obvious, and has syntax
error.

Shi Mu wrote:

How to run a function to make [1,2,4] become [[1,2],1,4],[2,4]]?
Thanks!

[Adonis]

Shi Mu wrote:

How to run a function to make [1,2,4] become [[1,2],1,4],[2,4]]?
Thanks!

From what I gather try:

a = [1,2,4]
n = list()
for i in a:
index = a.index(i) + 1
for x in a[index:]:
n.append([i, x])
print n

more elegant ways to do this, but its a start.
hope this helps.

Adonis

[Adonis]

Shi Mu wrote:

How to run a function to make [1,2,4] become [[1,2],1,4],[2,4]]?
Thanks!

From what I gather try:

a = [1,2,4]
n = list()
for i in a:
index = a.index(i) + 1
for x in a[index:]:
n.append([i, x])
print n

more elegant ways to do this, but its a start.
hope this helps.

Adonis

[rurpy]

Shi Mu wrote:

How to run a function to make [1,2,4] become [[1,2],1,4],[2,4]]?
Thanks!

You want [[1,2],[1,4],[2,4]]? That is, all combinations of 2 items
from
the list? You might want to look at:
http://aspn.activestate.com/ASPN/Coo.../Recipe/190465

import * from xpermutations
[x for x in UniqueCombinations ([1,2,4], 2)]

[[1, 2], [1, 4], [2, 4]]

That web page also gives urls to other recipies that do the same thing.

[rurpy]

Shi Mu wrote:

How to run a function to make [1,2,4] become [[1,2],1,4],[2,4]]?
Thanks!

You want [[1,2],[1,4],[2,4]]? That is, all combinations of 2 items
from
the list? You might want to look at:
http://aspn.activestate.com/ASPN/Coo.../Recipe/190465

import * from xpermutations
[x for x in UniqueCombinations ([1,2,4], 2)]

[[1, 2], [1, 4], [2, 4]]

That web page also gives urls to other recipies that do the same thing.

[Jeffrey Schwab]

ru***@yahoo.com wrote:

Shi Mu wrote:

How to run a function to make [1,2,4] become [[1,2],1,4],[2,4]]?
Thanks!

You want [[1,2],[1,4],[2,4]]? That is, all combinations of 2 items
from
the list? You might want to look at:
http://aspn.activestate.com/ASPN/Coo.../Recipe/190465

import * from xpermutations
[x for x in UniqueCombinations ([1,2,4], 2)]

[[1, 2], [1, 4], [2, 4]]

That web page also gives urls to other recipies that do the same thing.

Dang, that's better than my version.

$ ./combinations.py 2 1 2 4
[['1', '2'], ['1', '4'], ['2', '4']]

def combinations( universe, n=None ):

"""
Return all possible combinations of length "n," where the
elements of each combination are taken from the list "universe."
"""

result = []

if n == None:
n = len( universe )

if n > len( universe ):
# No combination of elements can have cardinality
# greater than universe, which is by definition the list
# of all possible elements.
pass
elif n < 0:
# No combination can have negative cardinaltiy.
pass
elif n == 0:
# Only the empty combination has cardinality 0.
result.append( [ ] )
else: # 0 < n <= len( universe )
for i in xrange( len( universe ) ):
elem = universe[i]
post = universe[i+1:]
for c in combinations( post, n - 1 ):
choice = [ elem ]
choice.extend( c )
result.append( choice )

return result

if __name__ == "__main__":

import sys

if len( sys.argv ) < 2:
sys.stderr.write(
"usage: %s <n> [elements ...]\n" % sys.argv[0] )
sys.exit(1)

n = int( sys.argv[1] )
print repr( combinations( sys.argv[2:], n ) )

[Jeffrey Schwab]

ru***@yahoo.com wrote:

Shi Mu wrote:

How to run a function to make [1,2,4] become [[1,2],1,4],[2,4]]?
Thanks!

You want [[1,2],[1,4],[2,4]]? That is, all combinations of 2 items
from
the list? You might want to look at:
http://aspn.activestate.com/ASPN/Coo.../Recipe/190465

import * from xpermutations
[x for x in UniqueCombinations ([1,2,4], 2)]

[[1, 2], [1, 4], [2, 4]]

That web page also gives urls to other recipies that do the same thing.

Dang, that's better than my version.

$ ./combinations.py 2 1 2 4
[['1', '2'], ['1', '4'], ['2', '4']]

def combinations( universe, n=None ):

"""
Return all possible combinations of length "n," where the
elements of each combination are taken from the list "universe."
"""

result = []

if n == None:
n = len( universe )

if n > len( universe ):
# No combination of elements can have cardinality
# greater than universe, which is by definition the list
# of all possible elements.
pass
elif n < 0:
# No combination can have negative cardinaltiy.
pass
elif n == 0:
# Only the empty combination has cardinality 0.
result.append( [ ] )
else: # 0 < n <= len( universe )
for i in xrange( len( universe ) ):
elem = universe[i]
post = universe[i+1:]
for c in combinations( post, n - 1 ):
choice = [ elem ]
choice.extend( c )
result.append( choice )

return result

if __name__ == "__main__":

import sys

if len( sys.argv ) < 2:
sys.stderr.write(
"usage: %s <n> [elements ...]\n" % sys.argv[0] )
sys.exit(1)

n = int( sys.argv[1] )
print repr( combinations( sys.argv[2:], n ) )