tests efficiency of string concatenation operations in python
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Copy to clipboard1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 | #! /usr/bin/env python
""" (Q): which way to use for concatenating strings?
(A): run the script and find out yourself.
"""
import time
bloated_string = 'bloat me' * 10
# method 1, simple concatenation
def slow():
test_string = ''
start = time.clock()
for i in range(1000):
test_string += bloated_string
end = time.clock()
delta = float(end-start)
# print 'slow len: ', len(test_string)
return delta
# method 2, use list.append() and ''.join()
def fast():
test_string = list()
start = time.clock()
for i in range(1000):
test_string.append('%s' % bloated_string)
test_string = ''.join(test_string)
end = time.clock()
delta = float(end-start)
# print 'fast len: ', len(test_string)
return delta
# method 3, use list comprehension and ''.join()
def fastest():
test_string = bloated_string
start = time.clock()
test_string = ''.join([test_string for i in range(1000)])
end = time.clock()
delta = float(end-start)
# print 'fastest len', len(test_string)
return delta
if __name__ == '__main__':
print '--- CPU TIMES ---'
delta_slow = slow()
print 'delta slow: {delta_slow}'.format(delta_slow=delta_slow)
delta_fast = fast()
print 'delta fast: {delta_fast}'.format(delta_fast=delta_fast)
delta_fastest = fastest()
print 'delta fastest: {delta_fastest}'.format(delta_fastest=delta_fastest)
print '---'
print 'listcomps is %f times faster than (list.append + ''.join())' % \
(delta_fast/delta_fastest)
print 'the latter is %f times faster (slower) than simple concat' %\
(delta_slow/delta_fast)
|
Why do you have fast() do a string interpolation?:
Correcting for that, list comprehensions are about 2x faster than loops, and joins are almost 2x faster than looped string
+concatenations.I stand corrected. Yes, %s takes some delta from .append() and then join. Thank you for the correction.