Measure the time taken by some Python code

timer.py

from collections import OrderedDict
from time import time

class Timer(object):
  """
  Measure the time taken by some Python code, incl. its subtasks:
  
    >>> with Timer('parent') as timer:
    ...   sleep(0.5)
    ...   with timer.child('child') as child:
    ...     sleep(.25)
    ...     with child.child('grandchild'):
    ...       sleep(.1)
    ... 
    >>> print(timer.summary)
    parent: 0.86s
      child: 0.36s
        grandchild: 0.10s
  """
  def __init__(self, name):
    self.name = name
    self.elapsed = 0.0
    self.start_time = None
    self.children = OrderedDict()
  def __enter__(self):
    self.start_time = time()
    return self
  def child(self, name):
    return self.children.setdefault(name, Timer(name))
  @property
  def summary(self):
    result_lines = ['%s: %.2fs' % (self.name, self.elapsed)]
    for child in self.children.values():
      for line in child.summary.split('\n'):
        result_lines.append('  ' + line)
    return '\n'.join(result_lines)
  def __exit__(self, *_):
    time_taken = time() - self.start_time
    self.elapsed += time_taken