廖雪峰python3 装饰器练习题

#装饰器
'''
def log(text):
    def decorator(func):
        def wrapper(*args, **kw):
            print('%s %s()' % (text, func.__name__))
            return func(*args, **kw)
        return wrapper
    return decorator

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

now()  #三层嵌套效果是：now = log('execute')(now)
'''
#请设计一个decorator，它可作用于任何函数上，并打印该函数的执行时间：
'''
import functools
import time
def metric(fn):
    @functools.wraps(fn)
    def wrapper(*args, **kw):
        start = time.time()
        x = fn(*args, **kw)
        print('%s execute in %s ms' % (fn.__name__, (time.time()-start)*1000))
        return x
    return wrapper
@metric
def fast(x, y):
    time.sleep(0.0012)
    return x + y;

@metric
def slow(x, y, z):
    time.sleep(1.2)
    return x * y * z;

f = fast(11, 22)
s = slow(11, 22, 33)
if f != 33:
    print('测试失败!')
elif s != 7986:
    print('测试失败!')
'''

#请编写一个decorator，能在函数调用的前后打印出'begin call'和'end call'的日志。
'''
import functools
import types
def log(obj = None):
    text = ""
    def decorator(fun):
        functools.wraps(fun)
        def wrapper(*args, **kw):
            print('{0}begin call {1}'.format(text, fun.__name__))
            x = fun(*args, **kw)
            print('{0}end call {1}'.format(text, fun.__name__))
            return x
        return wrapper
    if isinstance(obj, types.FunctionType) or isinstance(obj, types.BuiltinFunctionType):
        return decorator(obj)
    elif obj is None:
        text = ''
        return decorator
    else:
        text = obj+' '
        return decorator

@log('excute')
def fun1():
    print('hello world')
@log()
def fun2():
    print('hello world')
@log
def fun3():
    print('hello world')

fun1()
fun2()
fun3()
'''

这里面有一个小细节希望注意判断一个变量obj是否为函数：

if isinstance(obj, types.FunctionType) or is instance(obj, types.BuiltinFunctionType):

    print('obj is function')

types.FunctionType 和 types.BuiltinFunctionType的官方文档解释如下：

types. FunctionType types. LambdaType

The type of user-defined functions and functions created by lambda expressions.

types. BuiltinFunctionType types. BuiltinMethodType

The type of built-in functions like len() or sys.exit(), and methods of built-in classes. (Here, the term “built-in” means “written in C”.)