[Python-Dev] identity operands (was python-dev Summary for 2005-03-01 through 2005-03-15 [draft])

[Timothy Fitz]

[Nick Coghlan]
> So, using "".join is roughly three times as fast as abusing sum :)

True in the case where you're concatenating three strings, but what
about 100 strings?

(Full source attached)
Py> timeit.Timer("sum(strings, ai)", setup).repeat()
[33.553668413164239, 32.861660909417253, 33.092705357803851]
Py> timeit.Timer("''.join(strings)", setup).repeat()
[5.4385152302876492, 5.3633637794747671, 5.3587657090496066]
Py> timeit.Timer(" + ".join('"' + s + '"' for s in strings), "").repeat()
[17.726616371633828, 17.785511845779279, 18.179861127601413]

So at 100 strings, the difference is over 5x, and I assume you'll see
the relative distance increase as you increase the number of strings.

Timothy Fitz
-------------- next part --------------
import timeit
from random import choice
from random import randrange
from string import uppercase

setup = """
class additive_identity(object):
 def __add__(self, other):
  return other

ai = additive_identity()

from random import choice
from random import randrange
from string import uppercase
strings = ["".join(choice(uppercase) for i in range(randrange(10))) for i in range(100)]"""

strings = ["".join(choice(uppercase) for i in range(randrange(10))) for i in range(100)]

print "SUM:", timeit.Timer("sum(strings, ai)", setup).repeat()
print "JOIN:", timeit.Timer("''.join(strings)", setup).repeat()
print "ADD:", timeit.Timer(" + ".join('"' + s + '"' for s in strings), "").repeat()