how to measure execution time of functions (automatically) in Python

One way to do this would be with a decorator (PEP for decorators) (first of a series of tutorial articles on decorators). Here’s an example that does what you want.

from functools import wraps
from time import time

def timed(f):
  @wraps(f)
  def wrapper(*args, **kwds):
    start = time()
    result = f(*args, **kwds)
    elapsed = time() - start
    print "%s took %d time to finish" % (f.__name__, elapsed)
    return result
  return wrapper

This is an example of its use

@timed
def somefunction(countto):
  for i in xrange(countto):
    pass
  return "Done"

To show how it works I called the function from the python prompt:

>>> timedec.somefunction(10000000)
somefunction took 0 time to finish
'Done'
>>> timedec.somefunction(100000000)
somefunction took 2 time to finish
'Done'
>>> timedec.somefunction(1000000000)
somefunction took 22 time to finish
'Done'