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gh-156675: Exclude annotations from the documented lambda grammar #159831

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17 changes: 13 additions & 4 deletions Doc/reference/expressions.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -2440,7 +2440,16 @@ Lambdas
single: : (colon); lambda expression

.. productionlist:: python-grammar
lambda_expr: "lambda" [`parameter_list`] ":" `expression`
lambda_expr: "lambda" [`lambda_parameter_list`] ":" `expression`
lambda_parameter_list: `lambda_defparameter` ("," `lambda_defparameter`)* "," "/" ["," [`lambda_parameter_list_no_posonly`]]
: | `lambda_parameter_list_no_posonly`
lambda_parameter_list_no_posonly: `lambda_defparameter` ("," `lambda_defparameter`)* ["," [`lambda_parameter_list_starargs`]]
: | `lambda_parameter_list_starargs`
lambda_parameter_list_starargs: "*" `identifier` ("," `lambda_defparameter`)* ["," [`lambda_parameter_star_kwargs`]]
: | "*" ("," `lambda_defparameter`)+ ["," [`lambda_parameter_star_kwargs`]]
: | `lambda_parameter_star_kwargs`
lambda_parameter_star_kwargs: "**" `identifier` [","]
lambda_defparameter: `identifier` ["=" `expression`]

Lambda expressions (sometimes called lambda forms) are used to create anonymous
functions. The expression ``lambda parameters: expression`` yields a function
Expand All @@ -2451,9 +2460,9 @@ object. The unnamed object behaves like a function object defined with:
def <lambda>(parameters):
return expression

See section :ref:`function` for the syntax of parameter lists. Note that
functions created with lambda expressions cannot contain statements or
annotations.
The rules for parameter lists are the same as for :ref:`function definitions
<function>`, except that annotations are not allowed. Functions created with
lambda expressions cannot contain statements or annotations.


.. index::
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