python 装饰器的奇怪语法规范

Question

funcdef        ::=  [decorators] "def" funcname "(" [parameter_list] ")" ["->" expression] ":" suite
decorators     ::=  decorator+
decorator      ::=  "@" dotted_name ["(" [parameter_list [","]] ")"] NEWLINE
dotted_name    ::=  identifier ("." identifier)*
parameter_list ::=  (defparameter ",")*
                    | "*" [parameter] ("," defparameter)* ["," "**" parameter]
                    | "**" parameter
                    | defparameter [","] )
parameter      ::=  identifier [":" expression]
defparameter   ::=  parameter ["=" expression]
funcname       ::=  identifier

似乎表明以下语法有效：

@some.dotted.name(*what : "is this")
def my_func(x):
    pass

但解释器不接受。是我看错语法了，还是语法不对？

Answer 1

我觉得这像是一个文档错误。

是

decorator      ::=  "@" dotted_name ["(" [argument_list [","]] ")"] NEWLINE

直到 v3.2，当 argument_list 更改为 parameter_list。这不可能是正确的，尽管提交 one-line patch 的人显然不这么认为。

grammar itself没有修改。它仍然说：

decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE

因为那是：

the full Python grammar, as it is read by the parser generator and used to parse Python source files

我想我们可以得出结论，Python 装饰器仍然具有我们所期望的语法。

python 装饰器的奇怪语法规范

Strange syntax specification for python decorators

python

grammar

annotations

decorator