Python 迭代器

Posted 2020-10-10

iter()函数和next()函数

使用iter(序列)函数可以获得一个迭代器，使用next(迭代器)函数可以获得迭代器中的下一条数据，例如；

l = [1,2,3]
s = ‘hello world‘
t = (1,2,3,‘hello‘)
 
it1 = iter(l)
it2 = iter(s)
it3 = iter(t)
 
print(next(it1)) # 1
print(next(it2)) # h
print(next(it3)) # 1

StopIteration 异常

当迭代器中没有数据时，会抛出一个StopIteration 异常，利用该异常判断迭代结束，例如：

l = [1,2,3]
it = iter(l)
while True:
    try:
        x = next(it)
        print(x)
    except StopIteration as si:
        # print(‘end‘)
        break
# 1 2 3

迭代字符串、列表、元组和字典

l = [1,2,3]
s = ‘hello world‘
t = (1,2,3,‘hello‘)
 
it1 = iter(l)
it2 = iter(s)
it3 = iter(t)
 
print(next(it1)) # 1
print(next(it2)) # h
print(next(it3)) # 1
 
# 字典
d = {‘pid‘:‘123‘,‘name‘:‘tom‘,‘age‘:‘20‘}
it = iter(d) # keys
 
for k in it:
    v = d[k]
    print(k,v ,end=‘ ‘)

使用for/while循环迭代

l = [1,2,3]


it = iter(l)
 
for x in it:
    print(x)
 
# 1 2 3


it = iter(l)
 
while True:
    try:
        x = next(it)
        print(x)
    except StopIteration as si:
        break
# 1 2 3