python decorator實例

1. 兩特性

 1.1. 在函數調用的前後打印出日誌

 1.2、decorator支持
    @log &&  @log('execute')

2. code

# -*- coding: utf-8 -*-

import functools

def log(s = None):
    def decorate(func):
        @functools.wraps(func)
        def wrapper(*args, **kw):
            print('Start')
            if isinstance(s, str):
                print('%s %s()' % (s, func.__name__))
            else:
                print('call %s()' % func.__name__)
            f = func(*args, **kw)
            print('Done')
            return f
        return wrapper

    return decorate

print "==================================="
print "========       @log()      ========"
print "==================================="
@log()
def now():
    print('2015-3-25')
now()


print "==================================="
print "======== @log('Lanuch')  ========  "
print "==================================="
@log("Lanuch ")
def now():
    print('2015-3-25')
now()


print "======   print now.__name__  ====="
print now.__name__

3. Test result

4. 總結

”def log(s = None)“中的“s = None”是1.2的關鍵。
也是解決“TypeError: log() takes exactly 1 argument (0 given)”的鑰匙。