python中的Timeit模块没有正确运行

Question

我正在尝试使用python的timeit模块，它似乎在timeit源代码中有错误(尽管这似乎不正确)。

下面是正在运行的代码片段:

def recordCuckoo(amtElements, loadFactor):
    '''
    Determines the average lookup speed in seconds of a cuckoo hash table
    with @amtElements elements and a load factor of @loadFactor
    '''
    mySetup = '''
    import Statistics
    import random
    import hashingLibrary
    from CuckooHashing import *
    '''

    controlStatement = "Statistics.timeCuckooControl(" + str(amtElements) + "," + str(loadFactor) + ")"
    testStatement = "Statistics.timeCuckoo(" + str(amtElements) + "," + str(loadFactor) + ")"
    controlTime = timeit.timeit(controlStatement, setup=mySetup, number=1)
    testTime = timeit.timeit(testStatement, setup=mySetup, number=1)
    lookupTime = (testTime - controlTime)/1000000
    print ("The average lookup time for a cuckoo table with {0} elements and a load factor of {1} was:".format(amtElements, loadFactor))
    print (lookupTime)
    return lookupTime
    if __name__ == "__main__":
        recordCuckoo(100, 0.5)

当我运行它时，我收到以下错误:

 Traceback (most recent call last):
  File "C:Python34CuckooHashingStatistics.py", line 308, in <module>
    recordCuckoo(100, 0.5)
  File "C:Python34CuckooHashingStatistics.py", line 267, in recordCuckoo
    controlTime = timeit.timeit(controlStatement, setup=mySetup, number=1)
  File "C:Python34libtimeit.py", line 213, in timeit
    return Timer(stmt, setup, timer).timeit(number)
  File "C:Python34libtimeit.py", line 122, in __init__
    code = compile(src, dummy_src_name, "exec")
  File "<timeit-src>", line 9
    _t0 = _timer()
                 ^
IndentationError: unindent does not match any outer indentation level

我知道错误很可能在键盘和椅子之间，但是我收到的错误似乎表明timeit模块中有一个不合适的空格/制表符。这是怎么回事?

Answer 1

您可以这样定义mySetup变量:

mySetup = '''
import Statistics
import random
import hashingLibrary
from CuckooHashing import *
'''

如果你考虑到这一点，这根本不是问题。但是，这些行实际上出现在函数声明中:

def recordCuckoo(amtElements, loadFactor):
    mySetup = '''
    import Statistics
    import random
    import hashingLibrary
    from CuckooHashing import *
    '''

因此，实际上mySetup的含量如下:

'''
    import Statistics
    import random
    import hashingLibrary
    from CuckooHashing import *
    '''

可以看到，在import行前面有一个缩进，这使得它们无效(因为它们在执行时没有预期的缩进)。因此，您应该以不同的方式设置setup变量:

def recordCuckoo(amtElements, loadFactor):
    mySetup = '''
import Statistics
import random
import hashingLibrary
from CuckooHashing import *
'''

或者像这样的:

def recordCuckoo(amtElements, loadFactor):
    mySetup = 'n'.join((
        'import Statistics',
        'import random',
        'import hashingLibrary',
        'from CuckooHashing import *'
    ))

Answer 2

以下测试可以工作:

timeit.timeit('a+3', setup='a=1', number=10000)
timeit.timeit('a+3 -float(2n)', setup='a=1', number=10000)
timeit.timeit(' a+3 -float(2n)', setup='a=1', number=10000)

但这失败了，你的错误:

timeit.timeit('a+3', setup=' a=1', number=10000)

注意setup中的空格。您可以通过传递mySetup.strip()来消除它。

在运行有问题的函数之前打印变量总是一个好主意，但是你感到困惑是正确的，错误是绝对神秘的。