一、匿名函数
1.1 普通函数定义
In [57]:
def add(x,y):
return x+y
print(add(1,2))
3
1.2 匿名函数定义： lambda 参数:结果
In [58]:
f = lambda x,y:x+y
print(f(1,2))
3
1.3 特点
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#### 无函数名、无return
二、三元表达式
2.1 格式：条件为真时返回的结果 if 条件判断 else 条件为假返回的结果
In [60]:
x,y = 1,2
r = x if x >y else y
print (r)
2
三、map
适用场景：数据映射
In [61]:
list_x = [1,2,3]
def square(x):
return x*x
In [62]:
r = map(square, list_x)
print(r)
print(list(r))
<map object at 0x04DF0570>
[1, 4, 9]
四、map与lambda
In [63]:
r = map(lambda x: x*x ,list_x)
print(list(r))
list_y = [1,2,3]
r = map(lambda x,y: x*x+y ,list_x ,list_y)
print(list(r))
[1, 4, 9]
[2, 6, 12]
五、reduce
reduce作为连续计算，一次的结果作为下一次的输入
In [64]:
from functools import reduce
r = reduce(lambda x,y :x+y ,list_x,10) # 10为初始值
print (r)
16
六、filter
In [65]:
list_x = [1,0,0,4]
r = filter(lambda x: True if x ==1 else False,list_x)
print(list(r))
[1]
lambda结合三元表达式，结合filter
七、装饰器
7.1 普通函数
In [66]:
import time
def f1():
print("this is a function")
f1()
this is a function
需求变更，需要在打印功能前打印时间
In [67]:
def print_current_time(func):
print(time.time())
func()
print_current_time(f1)
1532500830.52
this is a function
In [68]:
### 缺点：没有和特定函数关联，完全依赖于调用
7.2 装饰器
In [69]:
def decorator(func):
def wrapper():
print(time.time())
func()
return wrapper
f = decorator(f1)
f()
1532500830.641
this is a function
7.3 装饰器：@语法糖
In [70]:
@decorator
def f1():
print("this is a function")
f()
1532500830.69
this is a function
7.4 装饰器参数
In [71]:
def decorator2(func):
def wrapper(*args,**kw):
print(time.time())
func(*args,**kw)
return wrapper
In [72]:
@decorator2
def f2(name1,name2,**kw):
print(kw)
print(name1,name2)
f2("zhao","qian",a="sun",b="li")
1532500830.787
{'a': 'sun', 'b': 'li'}
zhao qian