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jepler commented Aug 17, 2026 •

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As pointed out in #155966, the exceptional half-integer (0.5, 1.5, etc) inputs of tanpi were not handled properly.

Now, these raise ValueError and this is tested by test.test_math through its list of test cases.

In the process of working on this, I noticed that I had incorrectly added duplicate test ids and that this was not treated as an error by the test harness. I have corrected this and made it part of the test.

Issue: math.tanpi is untested at its poles and no test-file flag fits #155966

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jepler added 3 commits

August 17, 2026 17:26


          pythongh-155966: Correct handling of tanpi(0.5) (python#155966)

886d4ac

As pointed out in the issue, the exceptional half-integer
(0.5, 1.5, etc) inputs of tanpi were not handled properly.

Now, these raise ValueError and this is tested by `test.test_math`
through its list of test cases.


          math_testcases: Fix duplicate test ids

faa1799


          test_math: Treat duplicate test ids as failure.

198937d

bedevere-app Bot added the awaiting review label

Aug 17, 2026

bedevere-app Bot mentioned this pull request

Aug 17, 2026

math.tanpi is untested at its poles and no test-file flag fits #155966

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          Add news entry

5bd16b9

skirpichev requested changes

Aug 18, 2026

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Misc/NEWS.d/next/Library/2026-08-17-17-39-41.gh-issue-155966.0YOADY.rst Resolved

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Lib/test/mathdata/math_testcases.txt Resolved

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Lib/test/mathdata/math_testcases.txt Resolved

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bedevere-app Bot added awaiting core review and removed awaiting review labels

Aug 18, 2026

jepler and others added 4 commits

August 17, 2026 20:04


          Update Misc/NEWS.d/next/Library/2026-08-17-17-39-41.gh-issue-155966.0…

e59375b

…YOADY.rst

Co-authored-by: Sergey B Kirpichev <[email protected]>


          fix sign of infinity in test cases

9dff17a

the test harness cannot verify the sign of infinity, it can
only verify the exception; but it's good for it to be correct
anyhow.


          Revert "math_testcases: Fix duplicate test ids"

b4b4484

This reverts commit faa1799.


          fix only minimal set of testcase IDs

38f4d61

skirpichev approved these changes

Aug 18, 2026

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skirpichev requested a review from picnixz

August 18, 2026 01:48

skirpichev commented Aug 18, 2026

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CC @picnixz

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mdickinson reviewed

Aug 18, 2026

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Lib/test/mathdata/math_testcases.txt Resolved

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skirpichev reviewed

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Lib/test/mathdata/math_testcases.txt Resolved

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          Apply suggestion from @skirpichev

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mdickinson commented Aug 18, 2026

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Mildly off-topic: in case anyone's interested, there's some fun reading here: https://grouper.ieee.org/groups/msc/ANSI_IEEE-Std-754-2019/background/tanpi.txt

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          Merge branch 'main' into issue-155966

f7a4d0a

mdickinson commented Aug 21, 2026

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Thanks for the changes! LGTM (FWTW)

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picnixz approved these changes

Aug 21, 2026

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Sorry I forgot to approve!

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bedevere-app Bot added awaiting merge and removed awaiting core review labels

Aug 21, 2026

skirpichev commented Sep 9, 2026

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@picnixz, lets merge this.

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picnixz changed the title ~~gh-155966: Correct handling of tanpi(0.5) (#155966)~~ gh-155966: Correct handling of math.tanpi poles

Sep 9, 2026

picnixz merged commit 894af95 into python:main

Sep 9, 2026

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picnixz commented Sep 9, 2026

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I forgot that Mark relinquished his commit bit

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maurycy added a commit to maurycy/cpython that referenced this pull request

Sep 10, 2026


          Merge branch 'main' into tachyon-native-callable

e028ff5

* main: (158 commits)
  pythongh-156924: Try reifying lazy imports in `ForwarRef.evaluate()` (python#156940)
  pythongh-156233: Fix typos and code snippet errors in the docs (python#156475)
  pythongh-156837: Refer to yield expressions in generator function definitions (pythonGH-156863)
  pythongh-155292: Skip updating unicodedata with mismatched interpreter (pythonGH-157066)
  pythongh-157170: Document the scope of global curses settings (pythonGH-157207)
  pythongh-155966: Correct handling of `math.tanpi` poles (python#155980)
  pythongh-157170: Restore use_env() after test_use_prescr_screen in test_curses (pythonGH-157171)
  pythongh-156910: fix deadlock in type_set_abstractmethods under free-threading (python#156948)
  pythongh-155648: Write the empty and placeholder IDLE tests (python#156260)
  pythongh-153569: centralize formatted-string state and source spans (python#156484)
  pythongh-157137: Mark the PEP 820 soft deprecations as 3.15, not `next` (python#157138)
  pythongh-152433: Use regular LoadLibrary in UWP for Windows system libs (pythonGH-156972)
  pythongh-121617: Fix Py_CLEAR() memcpy in C++: replace NULL with _Py_NULL (python#157188)
  pythongh-157135: Fix documentation errors in the `math.atan{2}pi` functions (python#157136)
  pythongh-121617: Fix Py_CLEAR() in C++: replace NULL with _Py_NULL (python#157067)
  pythongh-156774: Speed up pdb startup with asyncio guard (python#156775)
  pythongh-156109: Allow static, non-framework iOS builds (python#156110)
  pythongh-156780: Emscripten: add missing EM_JS_DEPS (python#156798)
  pythongh-152936: Make privileged functions available on Android (python#152977)
  pythongh-123018: Keep the libedit history file header when truncating (pythonGH-157165)
  ...

clin1234 pushed a commit to clin1234/cpython that referenced this pull request

Sep 12, 2026


          pythongh-155966: Correct handling of math.tanpi poles (python#155980)

ccb0cd7

``math.tanpi`` now raises a ``ValueError`` for half-integer values
(e.g., ``tanpi(0.5)``), as these are poles of the function.

johnslavik pushed a commit to johnslavik/cpython that referenced this pull request

Sep 14, 2026


          pythongh-155966: Correct handling of math.tanpi poles (python#155980)

4f8cf8d

``math.tanpi`` now raises a ``ValueError`` for half-integer values
(e.g., ``tanpi(0.5)``), as these are poles of the function.

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jepler commented Aug 17, 2026 • edited by bedevere-app Bot Loading Uh oh! There was an error while loading. Please reload this page.

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skirpichev commented Sep 9, 2026

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jepler commented Aug 17, 2026 •

edited by bedevere-app Bot

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