timeit 在 python manage.py shell 中不起作用

Question

I have to find time taken to run query in django project ie python manage.py shell

code:

>>> import timeit
>>> d = {"a":1, "b":2}
>>> def a1():
...     for i in d:
...         a = i, d[i]
... 
>>> a1()


>>> print "Time 1:", timeit.timeit('a1()', 'from __main__ import a1 as a1')
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/lib64/python2.6/timeit.py", line 227, in timeit
    return Timer(stmt, setup, timer).timeit(number)
  File "/usr/lib64/python2.6/timeit.py", line 193, in timeit
    timing = self.inner(it, self.timer)
  File "<timeit-src>", line 3, in inner
ImportError: cannot import name a1
Time 1: >>>

This is not working in python manage.py shell

But this is working file I write code in py file and run my command line.

There is something wrong in from __main__ import a1 as a1

Answer 1

timeit is executed in a different context, so it does not have access to symbols you import/define.

To do so you can either:

Use the setup parameter of its constructor.

timeit.timeit("a1()", setup="from __main__ import a1 as a1")

Use the globals parameter (Python >= 3.5) of its constructor to pass the global namespace.

timeit.timeit("a1()", globals=globals())

See the doc for more details.

Answer 2

I have encountered the same problem and have found no real solution. What works for a few lines of code like the one in your example, is putting them directly in the setup parameter of timeit():

>>> setup = 'd={"a":1, "b":2}\ndef a1():\n    for i in d:\n        a = i, d[i]\n'
>>> print "Time 1:", timeit.timeit('a1()', setup)
Time 1: 0.337239027023

Yet, while it does not help explain why the import in timeit doesn't work in the django shell, why not implement your own timing function?

>>> import time 
>>> def time_function(fnc, number=10**6):
>>>     start = time.time()
>>>     for i in xrange(number):
>>>         fnc()
>>>     return time.time() - start

>>> print "Time 1:", time_function(a1)
Time 1: 0.3310558795928955