生成器,迭代器

1、有规律的列表，[] ==> () 生成器

a = [x for x in range(9)]

2、规律很难有一个简单表达式表示出来

斐波拉契数列（Fibonacci）
前两个数之和等于3个数

def fib(max):
    first,second,index = 1,1,0
    while index < max:
        first,second = second,first+second
        print(first)
        index += 1

xss
sql web

"""
    斐波拉契生成1.0版
"""
# def fib(max):
#   first,second,index = 1,1,0
#   while index < max:
#       first,second = second,first+second
#       print(first)
#       index += 1

# fib(10)


"""
    斐波拉契生成1.0版
    如果生成的数列数据特别庞大的时候，内存的占有就很大
"""
# ls = []
# def fib(max):
#   first,second,index = 1,1,0
#   while index < max:
#       first,second = second,first+second
#       ls.append(first)
#       index += 1

# fib(10)
# print(ls)

def fib(max):
    if max == 1:
        return  1
    if max == 2:
        return  2
    return fib(max-1) + fib(max - 2)


# yield关键字，会将函数转换为一个生成器
# def fib(max):
#     first,second,index = 1,1,0
#     while index < max:
#         first,second = second,first+second
#         yield first # 暂停一下，返回一个返回值 只能用next接受
#         index += 1
#
# res = fib(10)
# print(res)

#
# def fib(max):
#     first,second,index = 1,1,0
#     while index < max:
#         first,second = second,first+second
#         print("yield之前")
#         yield first
#         print("yield之后")
#         index += 1

# yield关键字生成生成器时，调用函数，该函数不会执行，只会转化为生成器，返回给返回值
# res = fib(10)
# print(res)
# print(next(res))
# print(next(res))
# for x in res:
#     print(x)

""""
send主要用于控制生成器的流程
"""
def demo1():
    while True:
        temp = yield 1
        if temp == 1:
            print("打印数据")
        elif temp == 2:
            print("存储数据")
        elif temp == 3:
            print("展示数据")

res = demo1()
# 我们使用send来控制生成器函数的流程的时候
# 应该首先让生成器next
next(res)
res.send(2)
res.send(1)

iter()可以将可迭代的对象转换为迭代器

# ls = [1,3,4,45,6,67,77,]
# for x in ls:
#     print(x)

# t = (1,3,4,45,6,67,77,)
# for x in t:
#     print(x)

# str = "liujianhongisgoodman"
# for x in str:
#     print(x)

# dict = {"name":"liujianhong","age":16,"sex": "nan"}
# for k,v in dict.items():
#     print(k,v)

# ls = (x for x in range(100))
# for x in ls:
#     print(x)

from collections import Iterable,Iterator
#Iterable 类型用来判断是否可被迭代的对象
ls = (x for x in range(100))
a = 10
# 判断某个对象是否可以被迭代
# isTrue = isinstance(a,Iterable)
# print(isTrue)
dict = {"name":"liujianhong","age":16,"sex": "nan"}
t = (1,3,4,45,6,67,77,)
# iter 是一个全局函数
# 可以将可迭代的对象转换为迭代器
ts = iter(t)
print(isinstance(ts,Iterator))
print(ts.__next__())