Hello all,

I am relatively new to python but I am having an issue with custom

sort functions..

I am trying to sort a list of lists or tuples with arbitrary ascending

or descending sorts. For example given a list of tuples

('firstname','l astname','age') I want to be able to sort lastname

descending, firstname ascending and age ascending...

I wrote a custom function generator to generate a sort function based

on an input list of column numbers and sort direction. Sort seems to

sort the first column ascending regardless of what the sort function

says. I also googled this group for other solutions and found a more

elegant one than mine but with the same results.

Here is my code and result:

sortList = [('2','D'),('1', 'D'),('0','D')]

dataList = []

dataList.append (['a','a','b'])

dataList.append (['a','a','a'])

dataList.append (['a','a','c'])

dataList.append (['a','b','a'])

dataList.append (['a','b','b'])

dataList.append (['a','b','c'])

dataList.append (['a','c','a'])

dataList.append (['a','c','b'])

outStr = 'def custSort( a, b):\n'

depth = 1

for sortPair in sortList:

indent = " "

curDent = depth * indent

outStr += curDent + 'if a[' + sortPair[0] + '] == b[' +

sortPair[0] + ']:\n'

depth += 1

depth -= 1

outStr += curDent + indent + 'return 0\n'

for j in range( len(sortList)-1, -1, -1 ):

curDent = depth * indent

print sortList[j][1]

if sortList[j][1] == 'A':

compareSym = '>'

elif sortList[j][1] == 'D':

compareSym = '<'

else:

print 'SORT DIRECTION ERROR ' + sortList[j][1]

outStr += curDent + 'elif a[' + sortList[j][0] + '] ' + compareSym

+ ' b[' + sortList[j][0] + ']:\n'

outStr += curDent + indent + 'return 1\n'

outStr += curDent + 'else:\n'

outStr += curDent + indent + 'return -1\n'

depth -= 1

print outStr

exec( outStr )

dataList.sort( custSort )

print str( dataList )

*************** ************

results:

D

D

D

def custSort( a, b):

if a[2] == b[2]:

if a[1] == b[1]:

if a[0] == b[0]:

return 0

elif a[0] < b[0]:

return 1

else:

return -1

elif a[1] < b[1]:

return 1

else:

return -1

elif a[2] < b[2]:

return 1

else:

return -1

[['a', 'b', 'c'], ['a', 'a', 'c'], ['a', 'c', 'b'], ['a', 'b', 'b'],

['a', 'a', 'b'], ['a', 'c', 'a'], ['a', 'b', 'a'], ['a', 'a', 'a']]

and Manuel Garcia's solution and results:

sortList = [(0,-1),(1,-1),(2,-1)]

dataList = []

dataList.append (['a','a','b'])

dataList.append (['a','a','a'])

dataList.append (['a','a','c'])

dataList.append (['a','b','a'])

dataList.append (['a','b','b'])

dataList.append (['a','b','c'])

dataList.append (['a','c','a'])

dataList.append (['a','c','b'])

def make_sort_f(lis t0):

def f(a,b):

for (i,m) in list0:

if a[i] == b[i]: continue

return m * cmp(a[i],b[i])

return 0

return f

dataList.sort( make_sort_f( sortList ) )

print str(dataList)

Results:

[['a', 'c', 'b'], ['a', 'c', 'a'], ['a', 'b', 'c'], ['a', 'b', 'b'],

['a', 'b', 'a'], ['a', 'a', 'c'], ['a', 'a', 'b'], ['a', 'a', 'a']]

is this an issue with sort or is my code screwy? Thanks in advance

for any help!

Ken R.