>
> 1. Although you claim that the two pieces of code are equivalent, you have
>> not proven your claim. A unit test demonstrating that the two pieces of
>> code are equivalent **for all relevant strings** would be essential.
>>
>
> This one bugged me. The attached file tests ALL possible combinationes of
> blanks and tabs to an arbitrary width of leading whitespace (i.e. a width
> of 16 results in more 28 million tests). One function times the current
> function, one the new function, and one compares the results of applying
> both the functions to the same strings. I guess that takes care of **for
> all relevant strings**; just use a larger width.
>
-- Reinhard
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import time
def timer(func, *args, **kwargs):
repetitions = kwargs.get("repeat", 10)
start = time.clock()
result = None
i = 0
while i < repetitions:
result = func(*args)
i += 1
elapsed = time.clock() - start
print "Time elapsed:", elapsed
return (elapsed, result)
def computeLeadingWhitespaceWidth (s,tab_width):
"""Originial"""
w = 0
for ch in s:
if ch == ' ':
w += 1
elif ch == '\t':
w += (abs(tab_width) - (w % abs(tab_width)))
else:
break
return w
def computeLeadingWhitespaceWidth1(s,tab_width):
"""Original enhanced"""
w = 0
tw = abs(tab_width)
for ch in s:
if ch == ' ':
w += 1
elif ch == '\t':
w += (tw - (w % tw))
else:
break
return w
def computeLeadingWhitespaceWidth2(s, tab_width):
"""Alternative"""
t = s.expandtabs(abs(tab_width))
return len(t) - len(t.lstrip())
def testWidth():
"""
Time the functions with different functions.
An arbitrary test string is used.
Each test is repeated one million times.
"""
s = "\t \t \t \t Leo\tis\ta\tbrilliant\tprogram."
print s.expandtabs(4)
timer(computeLeadingWhitespaceWidth, s, -4, repeat=1000000)
timer(computeLeadingWhitespaceWidth1, s, -4, repeat=1000000)
timer(computeLeadingWhitespaceWidth2, s, -4, repeat=1000000)
def testAllWidth(n):
"""
Test all possible combinations of ' ' and '\t' up to <n> charcaters.
<n> specifies the width of the leading whitespace to be tested.
Be careful: The number of tests grows exponentially.
"""
def createTestStrings(n):
testStrings = [" ", "\t"]
for i in range(1, n):
t1 = [s + " " for s in testStrings]
t2 = [s + "\t" for s in testStrings]
testStrings = testStrings + t1
testStrings = testStrings + t2
# Add some characters at the end of the string
testStrings = [s + "abc" for s in testStrings]
print " Tests to be performed:", len(testStrings)
return testStrings
def timeOld(testStrings):
for s in testStrings:
w = computeLeadingWhitespaceWidth(s, -4)
def timeNew(testStrings):
for s in testStrings:
w = computeLeadingWhitespaceWidth2(s, -4)
def compareResults(testStrings):
errors = 0
for s in testStrings:
w1 = computeLeadingWhitespaceWidth(s, -4)
w2 = computeLeadingWhitespaceWidth2(s, -4)
if w1 != w2:
errors += 1
print " *** error:", s, w1, w2
print " Number of differences:", errors
print "start"
print "Create testStrings..."
testStrings = createTestStrings(n)
print "Start timing..."
print " Old function...",
timer(timeOld, testStrings, repeat=1)
print " New function...",
timer(timeNew, testStrings, repeat=1)
print "Compare functions..."
compareResults(testStrings)
print "done"
if __name__ == "__main__":
#testWidth()
testAllWidth(16)
