Question

>>> x = "hello world"
>>> y = reversed(x)
>>> z = ''.join(y)
>>> z
'dlrow olleh'
>>> y
<reversed object at 0x7f2871248b38>
>>> ''.join(y)
''
>>> x
'hello world'
>>> ''.join(y)
''
>>> z = ''.join(y)
>>> z
''

为什么在反向函数中执行联接操作后，下次将z的值作为空白字符串获取

Answer 1

这是因为reversed返回一个迭代器，当您对其应用操作时，它将“消耗”该元素。如果要将反转结果存储在变量中，联接是一种很好的方法。

from collections.abc import Iterator

print(isinstance(reversed("hello world"), Iterator)) # True

it = reversed("hello world")
for x in it:
    print(x) # Prints the letters

for x in it:
    print(x) # Do not print them, there are already "consumed"

Python3.5.2反向方法字符串

1 个答案: