with file('nima,'r') as f:
  print f.readline()

#encoding:utf-8
class echo:
  def __enter__(self):
    print 'enter'
 
  def __exit__(self,*args):
    print 'exit'
 
with echo() as e:
  print 'nima'

from contextlib import contextmanager
 
@contextmanager
def make_context() :
  print 'enter'
  try :
    yield {}
  except RuntimeError, err :
    print 'error' , err
  finally :
    print 'exit'
 
with make_context() as value :
  print value

from contextlib import contextmanager
from random import random
 
DEFAULT_EXPIRES = 15
DEFAULT_RETRIES = 5
 
@contextmanager
def dist_lock(key, client):
  key = 'lock_%s' % key
 
  try:
    _acquire_lock(key, client)
    yield
  finally:
    _release_lock(key, client)
 
def _acquire_lock(key, client):
  for i in xrange(0, DEFAULT_RETRIES):
    get_stored = client.get(key)
    if get_stored:
      sleep_time = (((i+1)*random()) + 2**i) / 2.5
      print 'Sleeipng for %s' % (sleep_time)
      time.sleep(sleep_time)
    else:
      stored = client.set(key, 1)
      client.expire(key,DEFAULT_EXPIRES)
      return
  raise Exception('Could not acquire lock for %s' % key)
 
def _release_lock(key, client):
  client.delete(key)

class Context(object):
  
  def __init__(self):
    print '__init__()'

  def __enter__(self):
    print '__enter__()'
    return self

  def __exit__(self, exc_type, exc_val, exc_tb):
    print '__exit__()'

with Context():
  print 'Doing work in the context.'

__init__()
__enter__()
Doing work in the context.
__exit__()

class WithinContext(object):

  def __init__(self, context):
    print 'WithinContext.__init__(%s)' % context

  def do_something(self):
    print 'WithinContext.do_something()'

  def __del__(self):
    print 'WithinContext.__del__'


class Context(object):

  def __init__(self):
    print '__init__()'
  
  def __enter__(self):
    print '__enter__()'
    return WithinContext(self)
  
  def __exit__(self, exc_type, exc_val, exc_tb):
    print '__exit__()'

with Context() as c:
  c.do_something()

__init__()
__enter__()
WithinContext.__init__(<__main__.Context object at 0x7f579d8e4890>)
WithinContext.do_something()
__exit__()
WithinContext.__del__

class Context(object):

  def __init__(self, handle_error):
    print '__init__(%s)' % handle_error
    self.handle_error = handle_error
  
  def __enter__(self):
    print '__enter__()'
    return self
  
  def __exit__(self, exc_type, exc_val, exc_tb):
    print '__exit__(%s, %s, %s)' % (exc_type, exc_val, exc_tb)
    return self.handle_error

with Context(True):
  raise RuntimeError('error message handled')

print

with Context(False):
  raise RuntimeError('error message propagated')

__init__(True)
__enter__()
__exit__(<type 'exceptions.RuntimeError'>, error message handled, <traceback object at 0x7fdfb32f8b00>)

__init__(False)
__enter__()
__exit__(<type 'exceptions.RuntimeError'>, error message propagated, <traceback object at 0x7fdfb32f8b90>)
Traceback (most recent call last):
 File "test.py", line 23, in <module>
   raise RuntimeError('error message propagated')
   RuntimeError: error message propagated

import contextlib

@contextlib.contextmanager
def make_context():
  print ' entering'
  try:
    yield {}
   except RuntimeError, err:
    print ' Error:', err
  finally:
    print ' exiting'
    
print 'Normal:'

with make_context() as value:
  print ' inside with statement:', value
  
print
print 'handled ereor:'

with make_context() as value:
  raise RuntimeError('show example of handling an error')

print
print 'unhandled error:'

with make_context() as value:
  raise ValueError('this exception is not handled')

Normal:
 entering
 inside with statement: {}
  exiting

handled ereor:
entering
 Error: show example of handling an error
 exiting

unhandled error:
entering
exiting
Traceback (most recent call last):
 File "test.py", line 30, in <module>
   raise ValueError('this exception is not handled')
   ValueError: this exception is not handled

import contextlib

@contextlib.contextmanager
def make_context(name):
  print 'entering:', name
  yield name
  print 'exiting:', name

with contextlib.nested(make_context('A'), make_context('B'), make_context('C')) as (A, B,   C):
  print 'inside with statement:', A, B, C

entering: A
entering: B
entering: C
inside with statement: A B C
exiting: C
exiting: B
exiting: A

import contextlib

@contextlib.contextmanager
def make_context(name):
  print 'entering:', name
  yield name
  print 'exiting:', name

with make_context('A') as A, make_context('B') as B, make_context('C') as C:
  print 'inside with statement:', A, B, C

import contextlib


class Door(object):
  def __init__(self):
    print ' __init__()'
    
  def close(self):
    print ' close()'

print 'Normal Example:'
with contextlib.closing(Door()) as door:
  print ' inside with statement'
  
print 
print 'Error handling example:'
try:
  with contextlib.closing(Door()) as door:
    print ' raising from inside with statement'
    raise RuntimeError('error message')
except Exception, err:
  print ' Had an error:', err

Normal Example:
  __init__()
  inside with statement
  close()

Error handling example:
  __init__()
  raising from inside with statement
  close()
  Had an error: error message