迭代器(循环遍历)

for 语句就是触发这个迭代器的功能呢

for i in "chenshiba":
    print(i)
--------------------------
c
h
e
n
s
h
i
b
a

字典_迭代

linsk ={"name": "张三", "age":20, "sex":"男", "color":"red"}
for each in linsk:
    print("%s ---> %s" % (each, linsk[each]))
-------------------
name ---> 张三
age ---> 20
sex ---> 男
color ---> red

iter() next()迭代器

string = "chenshiba"
ti = iter(string)
print(next(ti))
print(next(ti))
print(next(ti))
print(next(ti))
------------------- # 不会在往下执行,, 如果后面没有了数据就会提示报错  StopIteration
c
h
e
n

while True:
    try:
        print(next(ti))
    except:
        break
while True:
    try:
        print(next(ti))
    except StopIteration:
        break
-------------------
c
h
e
n
s
h
i
b
a

-iter() -__iter()表示魔法方法的迭代器

class Fibs:
    def __init__(self, n=20):
        self.a = 0
        self.b =1
        self.n = n
    def __iter__(self):
        return self
    def __next__(self):
        self.a, self.b = self.b, self.a + self.b
        if self.a > self.n:
            raise StopIteration
        return self.a
f1 = Fibs()
for each in f1:
    if each <= 20:
        print(each)
    else:
        break
-----------------------------
1
1
2
3
5
8
13

升级版 , 可自定义参数

class Fibs:
    def __init__(self, n=20):
        self.a = 0
        self.b =1
        self.n = n
    def __iter__(self):
        return self
    def __next__(self):
        self.a, self.b = self.b, self.a + self.b
        if self.a > self.n:
            raise StopIteration
        return self.a
f1 = Fibs(100)
for each in f1:
    print(each)
-------------------------
1
1
2
3
5
8
13
21
34
55
89