iter()函數和next()函數

使用iter(序列)函數可以獲得一個叠代器，使用next(叠代器)函數可以獲得叠代器中的下一條數據，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 異常

當叠代器中沒有數據時，會拋出一個StopIteration 異常，利用該異常判斷叠代結束，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

叠代字符串、列表、元組和字典

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循環叠代

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

Python 叠代器