使用列表的Python扩展切片：文档正确吗？

Question

位于http://docs.python.org/reference/expressions.html#slicings的文档说（有一些摘录）：

5.3.3. Slicings

A slicing selects a range of items in a sequence object (e.g., a string, tuple or list).

slicing          ::=  simple_slicing | extended_slicing
simple_slicing   ::=  primary "[" short_slice "]"
extended_slicing ::=  primary "[" slice_list "]"
slice_list       ::=  slice_item ("," slice_item)* [","]
slice_item       ::=  expression | proper_slice | ellipsis
proper_slice     ::=  short_slice | long_slice
short_slice      ::=  [lower_bound] ":" [upper_bound]
long_slice       ::=  short_slice ":" [stride]
lower_bound      ::=  expression
upper_bound      ::=  expression
stride           ::=  expression
ellipsis         ::=  "..."

The semantics for a simple slicing are as follows. The primary must evaluate to a sequence object...

The semantics for an extended slicing are as follows. The primary must evaluate to a mapping object, ...

问题：

为了支持[1,2,3][a:b:c]符号，语言引用要求列表是映射对象（stride只有“扩展切片”才存在，这是用于映射对象的）。那么，语言引用是否中断了（可能他们只是在引入What's New in Python2.3: Extended Slices 时忘了更新它？）？在

此外，切片显然不仅仅适用于序列对象（参见上面的第一个短语）。在

还是只有我？；）

p.S.

有趣的是，python3文档在http://docs.python.org/release/3.1.3/reference/expressions.html#slicings上说：

A slicing selects a range of items in a sequence object (e.g., a string, tuple or list)...

["unified" slicing definition, not differentiating between "exteneded" and "simple" here]

The semantics for a slicing are as follows. The primary must evaluate to a mapping object, ...

Answer 1

不幸的是，New和langref使用了“扩展切片”的两个不同定义。两份文件各自的定义都是正确的。在