# PEP 661: Sentinel Values

**URL:** <https://discuss.python.org/t/pep-661-sentinel-values/9126>\
**Category:** PEPs\
**Created:** [June 6, 2021, 8:07am UTC](https://discuss.python.org/t/pep-661-sentinel-values/9126 "2021-06-06T08:07:06Z")\
**Posts on this page:** 1\
**Showing post:** 31

<div class="post-metadata">

**Author:** ![cben](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/cben/32/872_2.png) [@cben](https://discuss.python.org/u/cben)\
**Post date:** [June 9, 2021, 4:20pm UTC](https://discuss.python.org/t/pep-661-sentinel-values/9126/31 "2021-06-09T16:20:37Z")

</div>

Another point maybe worth discussing in the PEP is “sentinels” vs “symbols”.  
In languages that have symbols, they work like “duck enums”, in that 2 independent modules can construct the very same symbol.

It seems to me from reading the Rejected ideas there is concensus that’s an anti-goal. We want a way to get a “dedicated and distinct sentinel” without worrying someone else would produce it (other than by importing from the module where it was defined).

Plus Python has a long history of using regular strings (or interned strings when `is` matters) in most scenarios other languages would use symbols.

---

_[View the full topic](https://discuss.python.org/t/pep-661-sentinel-values/9126)._