标签：return 推导 Python inner func time print 装饰 def
1.装饰器
v = 1
v = 2
def func():
pass
v = 10
v = fun # 变量v指向了函数func
def base():
print(1)
def bar():
print(2)
bar = base
bar()
def func():
def inner():
pass
return inner
v = func()
print(v) # inner函数 <function func.<locals>.inner at 0x11fa53b00>
def func(arg):
def inner():
print(arg)
return inner
v1 = func(1)
v2 = func(2)
print(v1, v2) # <function func.<locals>.inner at 0x11fa507c0> <function func.<locals>.inner at 0x11fa50860>
def func(arg):
def inner():
arg()
return inner
def f1():
print(123)
v1 = func(f1)
v1()
def func(arg):
def inner():
arg()
return inner
def f1():
print(123)
return 666
v1 = func(f1)
result = v1() # 执行inner函数 f1含函数 ---> 123
print(result) # None
def func(arg):
def inner():
return arg() # v = arg() return v
return inner
def f1():
print(123)
return 666
v1 = func(f1)
result = v1() # 执行inner函数 f1含函数 ---> 123
print(result) # 666
def func():
print(1)
v1 = func
func = 666
v1()
print(func)
def func(arg):
def inner():
print('Before')
v = arg()
print('After')
return v
return inner
def index():
print('123')
return '666'
# 示例1
v1 = index() # 执行index函数，打印123并返回666赋值给v1
print(v1)
# 示例2
v2 = func(index) # v2是inner函数，arg即index函数
index = 666
v3 = v2()
print(v3)
# 示例3
v4 = func(index)
index = v4 # index指向了inner函数
index()
# 示例4
index = func(index)
index()
###################################################
def func(arg):
def inner():
v = arg()
return v
return inner
# 第1步：执行func函数并将下面的函数名当做参数传递，相当于：func(index)
# 第2步：将func的返回值重新赋值给下面的函数名，相当于：index = func(index)
@func
def index():
print(123)
return 666
print(index) # <function func.<locals>.inner at 0x11feb2c00>
- 1.3 一个和装饰器有关的案例——计算函数执行时间
import time
def func1():
time.sleep(2)
print(123)
def func2():
time.sleep(1)
print(123)
def func3():
time.sleep(1.5)
print(123)
start_time1 = time.time() # 获取当前时间
func1()
end_time1 = time.time() # 获取当前时间
print(end_time1-start_time1)
start_time2 = time.time() # 获取当前时间
func2()
end_time2 = time.time() # 获取当前时间
print(end_time2-start_time2)
start_time3 = time.time() # 获取当前时间
func3()
end_time3 = time.time() # 获取当前时间
print(end_time3-start_time3)
- 用装饰器编写：代码重用
- 在不改变原函数内部代码的基础上，在函数执行之前和之后自动执行某个功能
# 应用：计算函数执行时间
import time
def wrapper(func):
def inner():
start_time = time.time()
v = func()
end_time = time.time()
print(end_time-start_time)
return v
return inner
@wrapper
def func1():
time.sleep(2)
print(123)
@wrapper
def func2():
time.sleep(1)
print(123)
@wrapper
def func3():
time.sleep(1.5)
print(123)
func1()
###################################################
def x(func):
def y():
pass # 执行func函数前要做的事情
ret = func()
pass # 执行func函数后要做的事情
return ret
return y
# 装饰器的应用
@x
def index():
return 10
@x
def manage():
pass
# 执行函数，自动触发装饰器了
v = index()
print(v)
- 1.4 装饰器编写格式
def outer_func(param):
def inner_func(*args, **kwargs):
return param(*args, **kwargs)
return inner_func
# 问题：为什么要加*args **kwargs
@outer_func
def index():
pass
index()
def wrapper(func):
def inner(*args, **kwargs):
return func(*args, **kwargs)
return inner
@wrapper
def index():
print(1123)
index() # 无参数传递
@wrapper
def show(a1):
print(a1+100)
show(1) # 有参数传递
# index和show传递给装饰函数的参数func，在inner内部index和show会被调用，虽然两个函数被同一个装饰器装饰，
# 但参数个数不一定一致，所以要加可变参数
# 被装饰的函数index show可能不接收参数，也可能接收1个或多个参数，它们最后都会指向inner函数，所以inner
# 要带可变参数
2.列表推导式
v1 = [i for i in 可迭代对象]
v2 = [i for i in 可迭代对象 if 条件 ] # 条件为True才进行append
v1 = [i for i in 'alex']
v2 = [i + 100 for i in range(10)]
v3 = [99 if i>5 else 66 for i in range(10)]
print(v1, v2, v3)
def func():
return 100
v4 = [func for i in range(10)]
print(v4) # [<function func at 0x12e9d84a0>, <function func at 0x12e9d84a0>, <function func at 0x12e9d84a0>, <function func at 0x12e9d84a0>, <function func at 0x12e9d84a0>, <function func at 0x12e9d84a0>, <function func at 0x12e9d84a0>, <function func at 0x12e9d84a0>, <function func at 0x12e9d84a0>, <function func at 0x12e9d84a0>]
v5 = [lambda: 100 for i in range(10)]
result = v5[9]()
print(result)
def func():
return i
v6 = [func for i in range(10)]
result = v6[5]()
print(result)
v7 = [lambda:i for i in range(10)]
result = v7[5]()
print(result)
v8 = [lambda x:x*i for i in range(10)] # 新浪微博面试题
# 1.请问 v8 是什么？ ---> 8个匿名函数
# 2.请问v8[0](2)的结果是什么？ 执行匿名函数 2*9
print(v8)
print(v8[0](2))
def num():
return [lambda x:i*x for i in range(4)]
# num()执行后返回了一个列表，列表元素是4个匿名函数，4个函数的内容一样
print([m(2) for m in num()])
3.集合推导式
v1 = {i for i in 'alexxe'}
print(v1)
4.字典推导式
v2 = {'K'+str(i):i for i in range(10)}
print(v2)
标签：return,
推导,
Python,
inner,
func,
time,
print,
装饰,
def
From： https://www.cnblogs.com/zjl-linux/p/18685783