> r += xlate[ord(i)]
r += i
Perhaps I'm going to have to create a signature and drop information
about this in every post to c.l.py, but repeated string additions are
slow as hell for any reasonably large lengthed string. It is much
faster to place characters into a list and ''.join() them.
def test_s(l):
.... t = time.time()
.... for i in xrange(100):
.... a = ''
.... for j in xrange(l):
.... a += '0'
.... return time.time()-t
.... def test_l(l):
.... t = time.time()
.... for i in xrange(100):
.... a = ''.join(['0' for j in xrange(l)])
.... return time.time()-t
.... i = 128
while i < 4097:
.... print test_s(i), test_l(i)
.... i *= 2
....
0.0150001049042 0.0309998989105
0.0469999313354 0.047000169754
0.140999794006 0.109000205994
0.343999862671 0.203000068665
0.905999898911 0.40700006485
2.56200003624 0.828000068665
At 256 characters long, it looks about even. Anything longer and
''.join(lst) is significantly faster.
When we do something like the below, the overhead of creating short
lists is significant, but it is still faster when l is greater than
roughly 2048:
a = []
for i in xrange(l):
a += ['0']
- Josiah
