![]() This document has been placed in the public domain.PEP 526 – Syntax for Variable Annotations | Following system colour scheme Selected dark colour scheme Selected light colour scheme Python Enhancement Proposals Used as a synonym for “callable” throughout this document. References and Footnotes Unless specifically stated, “function” is generally On real-world usage and necessity, than try to force all users We would rather let these conventions develop organically, based Interoperability conventions at this point would be premature. ![]() Despite yet more discussion, it was decided not to standardizeĪ mechanism for annotation interoperability.Parameterisation syntax, it was decided that this should also be Despite considerable discussion about a standard type.Standard library raised too many thorny issues. ![]() Higher-order functions was ultimately rejected as being moreĪppropriate for third-party libraries including them in the Special objects in the stdlib for annotating generator functions and Though discussed early on (, ), including. ![]() The BDFL rejected the author’s idea for a special syntax for addingĪnnotations to generators as being “too ugly”.ImplementationĪ reference implementation has been checked into the p圓k (formerly The Parameter object may change or other changes may be warranted. Relation to Other PEPs Function Signature Objects (PEP 362)įunction Signature Objects should expose the function’s annotations. The pydoc module should display the function annotations whenĭisplaying help for a function. Documentation for parameters and return values ( ).Function overloading / generic functions ( ).Let IDEs show what types a function expects and returns ( ).Products and packages that could make use of annotations. Some of these are presented here, grouped by what kind In the course of discussing annotations, a number of use-cases haveīeen raised. _annotations_ is an empty, mutable dictionary if there are noĪnnotations on the function or if the functions was created from Of a parameter any attempt to use return as a parameter name The return key was chosen because it cannot conflict with the name This key is present only if an annotation was supplied There is a special key in the _annotations_ mapping, Representing the evaluated annotation expression This attribute isĪ mutable dictionary, mapping parameter names to an object Once compiled, a function’s annotations are available via theįunction’s _annotations_ attribute. The lambda can always be changed to a function.Lambda could be changed to support annotations, by requiring Lambda’s syntax does not support annotations. ForĮxample, one library might use string-based annotations to provideĭecorator : dotted_name ')' ] NEWLINE decorators : decorator + funcdef : 'def' NAME parameters ':' suite parameters : '(' ')' typedargslist : (( tfpdef ',' ) * ( '*' ( ',' tname ) * | '**' tname ) | tfpdef ( ',' tfpdef ) * ) tname : NAME tfpdef : tname | '(' tfplist ')' tfplist : tfpdef ( ',' tfpdef ) * Lambda These annotation consumersĬan do anything they want with a function’s annotations. The only way that annotations take on meaning is when they are These expressions available as described in Accessing Function Function annotations are nothing more than a way of associatingĪrbitrary Python expressions with various parts of a function atīy itself, Python does not attach any particular meaning or.Function annotations, both for parameters and return values, are.Python 3.0’s function annotations, let’s first talk broadly about Fundamentals of Function Annotationsīefore launching into a discussion of the precise ins and outs of Mechanism and syntax that has existed until this point. Information, reducing the confusion caused by the wide variation in This PEP aims to provide a single, standard way of specifying this Utilise the decorators introduced in PEP 318, while others parse aįunction’s docstring, looking for annotations there. This PEP introduces a syntax for adding arbitrary metadata annotationsīecause Python’s 2.x series lacks a standard way of annotating aįunction’s parameters and return values, a variety of toolsĪnd libraries have appeared to fill this gap. Tony Lownds Status : Final Type : Standards Track Created : 0 Python-Version : 3.0 Post-History : Toggle light / dark / auto colour theme PEP 3107 – Function Annotations Author : Collin Winter , PEP 3107 – Function Annotations | Following system colour scheme Selected dark colour scheme Selected light colour scheme Python Enhancement Proposals
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