第十三节
一,匿名函数
匿名函数 == 一行函数
lambda == def == 关键字
函数体中存放的是代码
生成器体中存放的也是代码
就是yield导致函数和生成器的结果不统一
lambda x:x
# x,可以不写是普通函数的形参,可以不接受参数
# :后边是返回值,x必须写 是普通函数的函数值 (lambda只能返回一个数据类型)
print(lambda x:x)
print((lambda x:x+6)(5))
f = lambda x:x+6(5)
print(f.__name__)# 查看函数名字 lambda
f1 = lambda x,y,z,:(x,y,z) # :返回值必须是一个数据类型
print(f(1,2,3))# 输出一个元组(1,2,3)
print([lambda :5][0]())
print((lambda :5)())
a = lambda :5
a()
# 返回 5 5
lst = [lambda :i for i in range(5)]
print(lst[1]) # 返回的是索引1的函数内存地址
print(lst[0]()) # 调用函数,返回值,返回的是i最后一次循环所赋值lst = [] # [lambda x:x+1,lambda x:x+1]
for i in range(2):
lst.append(lambda x:x+1)
print(lst[-1](5)) # 输出6, lambda 5:5+1
lst = [lambda x:x+1 for i in range(5)] # 同上一个
print(lst[0](5))# 输出6, lambda 5:5+1
tu = (lambda :i for i in range(3)) # 生成器
print(next(tu)) # 没调用,就是返回函数地址
print(next(tu)()) # 记录上一次查看的位置,输出 1# 面试题拆解:
lst = []
for i in range(5):
def func():
return i
lst.append(func) # lst 里面放了5个func函数的地址
print(lst[1]) # 输出的是函数地址
print(lst[1]()) # 调用函数,返回的是i最后一次循环def func():
for i in range(3): # i = 0 1 2
def foo(): # foo1 foo2 foo3
return i
yield foo # foo1 foo2 foo3
g = func()
print(next(g)()) # foo1 返回的是值
print(next(g)()) # foo2
print(next(g)) # foo3 返回的是地址,没有调用
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lst = [lambda :i for i in range(3)] # lst中有三个lambda : i
print(lst[0]()) # 取的是最后一次i循环的值
-----------------------------------------------------
tu = (lambda : i for i in range(3)) # 生成器是把循环的每次值 都存放在一个地址中
print(next(tu)())
print(next(tu)()) # 每次都是yield 逐个提取
print(next(tu)())lst = [lambda x:x+5 for i in range(2)]
# lst = [lambda x:x+5,lambda x:x+5]
print([i(2) for i in lst]) # x = 2,
# 返回结果 [7,7]
# 以下为分解式子
lst = [] # [lambda x:x+5,lambda x:x+5]
for i in range(2):
lst.append(lambda x:x+5)
new_lst = []
for i in lst:
new_lst.append(i(2))
print(new_lst)
---------------------------------------------------
lst = (lambda x:x+5 for i in range(2))
print(i(2) for i in lst) # 是一个内存地址
print([i(2) for i in lst]) # 是列表的两个值,[7,7]
# 以下是分解
def func():
for i in range(2):
f = lambda x: x + 5
yield f
g = func()
lst = []
for i in g:
lst.append(i(2))
print(lst)lst = [lambda x:x*i for i in range(2)]
print([i(2) for i in lst]) #[2,2]
# 以下为分解式
lst = [] # [lambda x:x*i,lambda x:x*i]
for i in range(2):
lst.append(lambda x:x*i)
# print(i)
new_lst = []
for em in lst:
new_lst.append(em(2))
print(new_lst)lst = (lambda x:x*i for i in range(2))# 这是一个生成器
print([i(2) for i in lst]) #[0,2] # i为0的时候存储一次,i为1的时候存储一次
# 分解
def func():
for i in range(2):
f = lambda x:x*i
yield f
g = func()
lst = []
for i in g:
lst.append(i(2))
print(lst)func = lambda x:[i for i in x]
print(func('afafasd'))
# 将字符串转换列表['a', 'f', 'a', 'f', 'a', 's', 'd']
print(list('afafasd'))
二,内置函数Ⅱ
sep :每一个元素之间分割的方法 默认 ” “
print(1,2,3,sep="|")# 1|2|3
end : print执行完后的结束语句,默认\n
print(1,2,3,end="")
print(4,5,6,end="") # 1 2 34 5 6file : 文件句柄,默认显示到屏幕
print(1,2,3,4,file=open("test","w",encoding="utf-8"))
flush 刷新
sum : 求和,可迭代对象容器,容器的元素必须是数字
print(sum([1,2,2,1]))
print(sum([10,20,30,40],100))# 设置初始值abs : 绝对值
print(abs(-9))
dir : 查看当前对象的所有方法
print(dir(str))
zip : 拉链,当长度不一致时选择最短的进行合并
lst1 = [1,2,3,5]
lst2=["alex","wusir","元"]
print(list(zip(lst1,lst2))) # 拉链
# 面试题:
print(dict(zip(lst1,lst2)))
# {1: 'alex', 2: 'wusir', 3: '宝元'}format : 格式转换
print(format("alex",">20")) # 右对齐
print(format("alex","<20")) # 左对齐
print(format("alex","^20")) # 居中
# 进制转换:
# 将十进制转换成二进制 bin
print(format(12,"b"))
print(format(12,"08b"))
# 将十进制转换成八进制 oct
print(format(12,"o"))
print(format(12,"08o"))
# 将二进制转换成十进制 digit
print(format(0b11001,"d"))
# 将十进制转换成十六进制 hex
print(format(17,"x"))
print(format(17,"08x"))reversed : 反转
print(list(reversed("alex")))
# ['x', 'e', 'l', 'a']
print(list(reversed([1,2,3,4,5])))
# [5, 4, 3, 2, 1]filter : 过滤,1,指定过滤规则(函数名[函数的内存地址]) 2,要过滤的数据
lst = [1,2,3,4,5,6]
print(list(filter(lambda x:x>1,lst)))
# 分解
def func(a):
return a>1
print(list(filter(func,lst)))
-------------------------------------------------
# 底层代码
lst = [1,2,3,4,5,6]
def f(func,args):
new_lst = []
for i in args:
if func(i):
new_lst.append(i)
return new_lst
def func(a):
return a>1
print(f(func,lst)) # [2,3,4,5,6]
# fiter写法
print(list(filter(lambda x:x>2,[1,2,3,4,5])))lst = [{'id':1,'name':'alex','age':18},
{'id':1,'name':'wusir','age':17},
{'id':1,'name':'taibai','age':16},]
# 筛选年龄大于16岁的
print(list(filter(lambda x:x['age']>16,lst)))
--------------------------------------------------
def func(a):
return a>1
print(list(filter(func,[1,2,3,4,5])))
print(list(filter(lambda a:a>1,[1,2,3,4,5])))map : 映射函数(将每个元素都执行了执行的方法)
print([i*8 for i in [1,2,3,4]])
#[8, 16, 24, 32]
-----------------------------------------------------------
lst = []
for i in [1,-22,3,4,5,6]:
lst.append(abs(i))
lst.sort()
print(lst)# [1, 3, 4, 5, 6, 22]
------------------------------------------------------------
def map(argv,args):
lst = []
num = len(args) if len(args) < len(argv) else len(argv)
for i in range(num):
lst.append(argv[i] + args[i])
return lst
print(map([1,2,3,4],[3,4,5,6,7,8,9,0]))
print(list(map(lambda x,y:x+y,[1,2,3,4,5],[33,22,44,55])))
# [4, 6, 8, 10]sorted : 排序
print(sorted([1,2,3,4,5,6],reverse=True))
print(sorted([1,2,3,4,5,-6],reverse=True,key=abs))
lst = ["三国演义","红楼梦","铁道游击队","西游记","水浒传","活着"]
print(sorted(lst,key=len))
# [6, 5, 4, 3, 2, 1]
# [-6, 5, 4, 3, 2, 1]
# ['活着', '红楼梦', '西游记', '水浒传', '三国演义', '铁道游击队']
-----------------------------------------------------------------
print(sorted([1,-22,3,4,5,6],key=abs)) # key指定排序规则
#[1, 3, 4, 5, 6, -22]
------------------------------------------------------------------
lst = [{"age":19},{"age1":20},{"age2":80},{"age3":10}]
print(sorted(lst,key=lambda x:list(x.values()))) # 值排序
print(sorted(lst,key=lambda x:list(x.keys()),reverse=True)) # 键排序max : 最大值
min : 最小值
print(max(10,12,13,15,16))
print(max([10,12,13,15,-16],key=abs))
# 16 -16reduce : 累计算
from functools import reduce
# 从 functools工具箱中拿来了reduce工具
from functools import reduce
def func(x,y):
return x+y
print(reduce(func,[1,2,3,4,5]))
print(reduce(lambda x,y:x+y,[1,2,3,4,5]))
# 15 15
三,闭包
什么是闭包?
在嵌套函数内,使用非本层变量和非全局变量就是闭包
闭包的作用:
1,保护数据的安全性。2,装饰器
__colsure__查看是是否为闭包
函数执行完后,函数体内文件自动销毁
例一:
def wrapper():
a = 1
def inner():
print(a)
return inner
ret = wrapper() # 闭包
例二:
a = 2
def wrapper():
def inner():
print(a)
return inner
ret = wrapper() # 不是
例三:
def wrapper(a,b):
def inner():
print(a)
print(b)
inner()
a = 1
b = 2
wrapper(a,b)