python 语法中的`~` 是什么意思
What is the meaning of `~` in python grammar
我正在浏览 python grammer specification 并找到以下语句，
for_stmt:
| 'for' star_targets 'in' ~ star_expressions ':' [TYPE_COMMENT] block [else_block]
~在这个语法规则中是什么意思？。语法中使用的其他符号（如 &、!、|）已经记录在案，但没有 ~.
The notation is a mixture of EBNF and PEG. In particular, & followed
by a symbol, token or parenthesized group indicates a positive
lookahead (i.e., is required to match but not consumed), while !
indicates a negative lookahead (i.e., is required not to match). We
use the | separator to mean PEG’s “ordered choice” (written as / in
traditional PEG grammars)
.
它记录在 PEP 617 下的语法表达式中：
~
Commit to the current alternative, even if it fails to parse.
rule_name: '(' ~ some_rule ')' | some_alt
In this example, if a left parenthesis is parsed, then the other alternative won’t be considered, even if some_rule or ‘)’ fail to be parsed.
~ 基本上表明，一旦达到它，您就被锁定在特定规则中，如果解析失败，则无法进入下一条规则。
PEP 617 前面提到 | some_alt 可以写在下一行
我正在浏览 python grammer specification 并找到以下语句，
for_stmt:
| 'for' star_targets 'in' ~ star_expressions ':' [TYPE_COMMENT] block [else_block]
~在这个语法规则中是什么意思？。语法中使用的其他符号（如 &、!、|）已经记录在案，但没有 ~.
The notation is a mixture of
EBNFandPEG. In particular,&followed by a symbol, token or parenthesized group indicates a positive lookahead (i.e., is required to match but not consumed), while!indicates a negative lookahead (i.e., is required not to match). We use the|separator to mean PEG’s “ordered choice” (written as/in traditional PEG grammars)
.
它记录在 PEP 617 下的语法表达式中：
~
Commit to the current alternative, even if it fails to parse.
rule_name: '(' ~ some_rule ')' | some_altIn this example, if a left parenthesis is parsed, then the other alternative won’t be considered, even if some_rule or ‘)’ fail to be parsed.
~ 基本上表明，一旦达到它，您就被锁定在特定规则中，如果解析失败，则无法进入下一条规则。
PEP 617 前面提到 | some_alt 可以写在下一行