Why does list () with an object show different results respectively?

Question

Result None

the list(a)

second time. Does anyone know about this?

>>> test = {1: 2, 3: 4}
>>> a= test.iterkeys()
>>> list(a)
**[1, 3]**
>>> list(a)
**[]**
>>> list(a)
[]

+3

Chen sun May 30 '17 at 19:15

1 answer

ForceBru · Answer 1 · 2017-05-30T19:18:18+0000

iterkeys

returns an iterator that, like any iterator, can only be iterated once.

list

consumes the entire iterator, so the latter cannot supply more values, so subsequent lists are empty.