joining list elements

[Mike Fletcher]

Hmm, from an old thread, I _think_ this was the best we came up with (note,
despite the doc string, the weird stuff is mostly my fault)...

import copy, types, sys
from types import ListType, TupleType # this now only supports the obsolete
stuff...

def hyperCollapse( inlist, allowedmap, type=type, list=list,
itype=types.InstanceType, maxint= sys.maxint):
	'''
	Destructively flatten a mixed hierarchy to a single level.
	Non-recursive, many speedups and obfuscations by Tim Peters :)
	'''
	try:
		# for every possible index
		for ind in xrange( maxint):
			# while that index currently holds a list
			expandable = 1
			while expandable:
				expandable = 0
				if allowedmap.has_key( type(inlist[ind]) ):
					# expand that list into the index
(and subsequent indicies)
					inlist[ind:ind+1] = list(
inlist[ind])
					expandable = 1
				
				# alternately you could iterate through
checking for isinstance on all possible
				# classes, but that would be very slow
				elif type( inlist[ind] ) is itype and
allowedmap.has_key( inlist[ind].__class__ ):
					# here figure out some way to
generically expand that doesn't risk
					# infinite loops...
					templist = []
					for x in inlist[ind]:
						templist.append( x)
					inlist[ind:ind+1] = templist
					expandable = 1
	except IndexError:
		pass
	return inlist

	
Here's a less crufty version for just hierarchies of lists...


def collapse(inlist, type=type, ltype=types.ListType, maxint= sys.maxint):
	'''
	Destructively flatten a list hierarchy to a single level. 
	Non-recursive, and (as far as I can see, doesn't have any
	glaring loopholes).
	Further speedups and obfuscations by Tim Peters :)
	'''
	try:
		# for every possible index
		for ind in xrange( maxint):
			# while that index currently holds a list
			while type(inlist[ind]) is ltype:
				# expand that list into the index (and
subsequent indicies)
				inlist[ind:ind+1] = inlist[ind]
			#ind = ind+1
	except IndexError:
		pass
	return inlist

Enjoy yourself,
Mike

-----Original Message-----
From: johannes at zellner.org [mailto:johannes at zellner.org]
Sent: Friday, October 13, 2000 11:45 PM
To: python-list at python.org
Subject: joining list elements


Hi again,

how do I join list elements ?

e.g. I want [[1, 2, 3], [4, 5, 6]] --> [1, 2, 3, 4, 5, 6]
     and    [[1, 2, 3],  4, 5, 6 ] --> [1, 2, 3, 4, 5, 6]
     and    [1, 2, 3], 4 --> [1, 2, 3, 4]

any help much appreciated!

-- 
   Johannes
-- 
http://www.python.org/mailman/listinfo/python-list