如何在不使用迭代器长度的情况下使用 python 中的 slice() 内置 function 获取迭代器的所有元素？

Question

If I have the following list: my_list = [1, 2, 3] . How can I take all the elements using slice() built-in method without knowing the length of my_list ?

my_list[slice(-1)] gives me [1, 2] and my_list[slice(':')] gives me a TypeError.

Is there something similar to my_list[:] that I can use with slice so that I can define a variable before the list is created?

Answer 1

You can pass None

>>> my_list = [1, 2, 3]
>>> id(my_list)
1827682884416
>>> copy = my_list[slice(None)]
>>> id(copy)
1827682861888
>>> copy
[1, 2, 3]
>>> my_list is copy
False

I believe that my_list[:] is just a syntactic sugar. You can confirm this by dis module.

>>> import dis
>>> dis.dis("my_list[:]")
  1           0 LOAD_NAME                0 (my_list)
              2 LOAD_CONST               0 (None)
              4 LOAD_CONST               0 (None)
              6 BUILD_SLICE              2
              8 BINARY_SUBSCR
             10 RETURN_VALUE