Description

pitrou

opened on Jan 31, 2022

Issue body actions

BPO	46593
Nosy	@mdickinson, @pitrou, @meadori, @corona10

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2022-01-31.15:29:00.019>
labels = ['interpreter-core', 'type-feature', '3.11']
title = 'memoryview lacks support for half floats'
updated_at = <Date 2022-01-31.15:54:50.040>
user = 'https://github.com/pitrou'

bugs.python.org fields:

activity = <Date 2022-01-31.15:54:50.040>
actor = 'corona10'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Interpreter Core']
creation = <Date 2022-01-31.15:29:00.019>
creator = 'pitrou'
dependencies = []
files = []
hgrepos = []
issue_num = 46593
keywords = []
message_count = 1.0
messages = ['412205']
nosy_count = 4.0
nosy_names = ['mark.dickinson', 'pitrou', 'meador.inge', 'corona10']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue46593'
versions = ['Python 3.11']

Activity

1. pitrou commented on Jan 31, 2022

   

   pitrou

   on Jan 31, 2022

   MemberAuthor

   More actions

   The struct module has support for half-floats (the "e" format code) but support is not fully enabled in the memoryview object.

   Let's contrast float32 (the "f" format code), which you can cast to, and read as Python objects:

   >>> a = np.array([0.0, -1.5], np.float32())
   >>> list(memoryview(a))
   [0.0, -1.5]
   >>> memoryview(a.tobytes()).cast('f').tolist()
   [0.0, -1.5]

   and float16, where support is minimal (casting forbidden, reading as Python objects unimplemented):

   >>> a = np.array([0.0, -1.5], np.float16())
   >>> list(memoryview(a))
   Traceback (most recent call last):
     File "<ipython-input-15-102982f8ac8e>", line 1, in <module>
       list(memoryview(a))
   NotImplementedError: memoryview: format e not supported
   
   >>> memoryview(a.tobytes()).cast('e').tolist()
   Traceback (most recent call last):
     File "<ipython-input-25-78df215a7360>", line 1, in <module>
       memoryview(a.tobytes()).cast('e').tolist()
   ValueError: memoryview: destination format must be a native single character format prefixed with an optional '@'
2. pitrou

   added

   3.11only security fixesonly security fixes

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   type-featureA feature request or enhancementA feature request or enhancement

   on Jan 31, 2022
3. ezio-melotti

   transferred this issue fromon Apr 10, 2022
4. corona10

   added 2 commits that reference this issue on Sep 10, 2022

   pythongh-90751: memoryview supports half-float

   3d897a2

   pythongh-90751: memoryview supports half-float

   61e926c
5. pitrou

   added 2 commits that reference this issue on Sep 10, 2022

   Merge branch 'pythongh-90751' of https://github.com/corona10/cpython …

   abf2050

   gh-90751: memoryview now supports half-float (#96738)

   8d75a13
6. corona10

   added

   3.12only security fixesonly security fixes

   and removed

   3.11only security fixesonly security fixes

   on Sep 11, 2022
7. corona10 commented on Sep 11, 2022

   

   corona10

   on Sep 11, 2022

   Member

   More actions

   @pitrou We can close this issue right?
8. pitrou commented on Sep 11, 2022

   

   pitrou

   on Sep 11, 2022

   MemberAuthor

   More actions

   Ah, sorry, I forgot it. Yes, we can.
9. pitrou

   closed this as completedon Sep 11, 2022
10. serhiy-storchaka

    added this to Struct, memoryview and array issues 🏗️on Jul 13, 2026
11. github-project-automation

    moved this to Todo in Struct, memoryview and array issues 🏗️on Jul 13, 2026
12. github-project-automation

    moved this from Todo to Done in Struct, memoryview and array issues 🏗️on Jul 13, 2026

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