scope - Getting "global name 'foo' is not defined" with Python's timeit

Question

I'm trying to find out how much time it takes to execute a Python statement, so I looked online and found that the standard library provides a module called timeit that purports to do exactly that:

import timeit

def foo():
    # ... contains code I want to time ...

def dotime():
    t = timeit.Timer("foo()")
    time = t.timeit(1)
    print "took %fs
" % (time,)

dotime()

However, this produces an error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in dotime
  File "/usr/local/lib/python2.6/timeit.py", line 193, in timeit
    timing = self.inner(it, self.timer)
  File "<timeit-src>", line 6, in inner
NameError: global name 'foo' is not defined

I'm still new to Python and I don't fully understand all the scoping issues it has, but I don't know why this snippet doesn't work. Any thoughts?

Answer 1

Change this line:

t = timeit.Timer("foo()")

To this:

t = timeit.Timer("foo()", "from __main__ import foo")

Check out the link you provided at the very bottom.

To give the timeit module access to functions you define, you can pass a setup parameter which contains an import statement:

I just tested it on my machine and it worked with the changes.