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Diffstat (limited to 'Doc/reference/expressions.rst')
| -rw-r--r-- | Doc/reference/expressions.rst | 13 |
1 files changed, 6 insertions, 7 deletions
diff --git a/Doc/reference/expressions.rst b/Doc/reference/expressions.rst index b1b80ca384..6f7e13f35b 100644 --- a/Doc/reference/expressions.rst +++ b/Doc/reference/expressions.rst @@ -517,25 +517,24 @@ or list). Slicings may be used as expressions or as targets in assignment or simple_slicing: `primary` "[" `short_slice` "]" extended_slicing: `primary` "[" `slice_list` "]" slice_list: `slice_item` ("," `slice_item`)* [","] - slice_item: `expression` | `proper_slice` | `ellipsis` + slice_item: `expression` | `proper_slice` 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: "..." - -.. index:: pair: extended; slicing There is ambiguity in the formal syntax here: anything that looks like an expression list also looks like a slice list, so any subscription can be interpreted as a slicing. Rather than further complicating the syntax, this is disambiguated by defining that in this case the interpretation as a subscription takes priority over the interpretation as a slicing (this is the case if the -slice list contains no proper slice nor ellipses). Similarly, when the slice -list has exactly one short slice and no trailing comma, the interpretation as a -simple slicing takes priority over that as an extended slicing. +slice list contains no proper slice). Similarly, when the slice list has +exactly one short slice and no trailing comma, the interpretation as a simple +slicing takes priority over that as an extended slicing. + +.. XXX is the next paragraph stil correct? The semantics for a simple slicing are as follows. The primary must evaluate to a sequence object. The lower and upper bound expressions, if present, must |