Implementation method is needed or desirable, whether the drawbacks mentionedĪre significant, nor which kind of implementation would be good. The discussion did not lead to any clear consensus on whether a standard Least one of the three aforementioned drawbacks. Methods used even within the stdlib, and that many of these suffer from at Need for sentinels is fairly common, that there are various implementation Sentinel values in the Python standard library. In the ensuing discussion, Victor Stinner supplied a list of currently used Instance being created and thus comparisons using is failing
Define sentinel how to#
about how to better implement a sentinel value for In May 2021, a question was brought up on the python-dev mailing list Way is not deemed necessary, and whether to do so is left to the discretion Note: Changing all existing sentinels in the stdlib to be implemented this In the stdlib and made publicly available as part of the stdlib. This PEP proposes adding a utility for defining sentinel values, to be used
Including some in the stdlib, suffer from several significant drawbacks. Have arisen over the years, but uncommon enough that there hasn’t been aĬlear need for standardization. TheseĬases are common enough that several idioms for implementing such sentinels Value is needed, usually when it needs to be distinct from None. However, sometimes an alternative sentinel Python has the special value None, which is intended to be used as suchĪ sentinel value in most cases. Missing data, such as NULL in relational databases or “N/A” (“not.Default values for function arguments, for when a value was not given:.Unique placeholder values, commonly known as “sentinel values”, are common in TL DR: See the Specification and Reference Implementation. Specific type signatures for each sentinel value.Define a recommended “standard” idiom, without supplying an implementation.Use the existing Ellipsis sentinel value.Add a single new sentinel value, such as MISSING or Sentinel.Toggle light / dark / auto colour theme PEP 661 – Sentinel Values Author : Tal Einat Discussions-To : Discourse thread Status : Draft Type : Standards Track Created : 0 Post-History : 0 PEP 661 – Sentinel Values | Following system colour scheme Selected dark colour scheme Selected light colour scheme Python Enhancement Proposals
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