idiom for initial list of lists

[Huaiyu Zhu]

Here's the timing results and program for various methods suggested here.
The winner (on my machine) is list_list.  It is suprising that list_tuple
did worse, and that copy_list is the worst.


Results of first run:

append_range     0.9065
append_list      0.8199
append_xrange    0.7929
listcmprh_range  0.7849
listcmprh_list   0.7160
listcmprh_xrange 0.6666
lambda_range     0.6246
lambda_list      0.5487
lambda_xrange    0.5250
list_list        0.4702
list_tuple       0.7277
copy_list        1.3493


Results of second run:

append_range     0.9144
append_list      0.9064
append_xrange    0.8002
listcmprh_range  0.7854
listcmprh_list   0.7144
listcmprh_xrange 0.6560
lambda_range     0.6248
lambda_list      0.5471
lambda_xrange    0.5181
list_list        0.4775
list_tuple       0.7328
copy_list        1.3472


The test program:

"""
init_list.py - timing of different ways to init list of list
"""

def append_range():
    S=[]
    for i in range(n):  S.append([])

def append_list():
    S=[]
    for i in [1]*n: S.append([])

def append_xrange():
    S=[]
    for i in xrange(n):  S.append([])

def lambda_range():
    S=map(lambda x:[], range(n))

def lambda_list():
    S=map(lambda x:[], [1]*n)

def lambda_xrange():
    S=map(lambda x:[], xrange(n))

def listcmprh_range():
    S=[[] for x in range(n)]

def listcmprh_list():
    S=[[] for x in [1]*n]

def listcmprh_xrange():
    S=[[] for x in xrange(n)]

def list_list():
    S=map(list, [[]]*n)

def list_tuple():
    S=map(list, [()]*n)

from copy import copy
def copy_list():
    S=map(copy, [[]]*n)


tests = [append_range, append_list, append_xrange,
        listcmprh_range, listcmprh_list, listcmprh_xrange,
        lambda_range, lambda_list, lambda_xrange,
        list_list, list_tuple, copy_list]

#------------------------------------------------------------------
from time import time
def timeit(f):
    _time = time()
    f()
    print "%-16s %.4f" % (f.__name__, time() - _time)

n = 100000
print n

#------------------------------------------------------------------
for f in tests:
    timeit(f)