Python with 用法

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lock
with 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, sys
from contextlib import closing

with closing(urllib.urlopen('http://www.yahoo.com')) as f:
    for line in f:
        sys.stdout.write(line)