• 打开文件

  with open('em.txt', 'wb') as f:    f.write('ememem')

• 线程lock

  lock = threading.Lock()# with里面获取lock, 退出with后释放lockwith lock:    # Critical section of code    ...

• 数据库游标

  db_connection = DatabaseConnection()with db_connection as cursor:    # with里面获取cursor, 退出with后释放cursor    cursor.execute('insert into ...')    cursor.execute('delete from ...')    # ... more operations ...

• 同时获取lock和数据库游标

  lock = threading.Lock()cur = db.cursor()with cur as cu, lock as locked:    ...

• 请求后关闭

  import urllib, sysfrom contextlib import closingwith closing(urllib.urlopen('http://www.yahoo.com')) as f:    for line in f:        sys.stdout.write(line)