8000 Misc improvements to the float tutorial by rhettinger · Pull Request #102052 · python/cpython · GitHub
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Misc improvements to the float tutorial #102052

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Merged
merged 10 commits into from
Feb 19, 2023
Merged

Misc improvements to the float tutorial #102052

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1e2ec34
Example is more intelligible without the leading zeros
rhettinger Feb 19, 2023
082d7a8
Leading zeros are easier to read and match the surrounding text.
rhettinger Feb 19, 2023
2ff520d
Compare sum() to straight addition and to math.fsum()
rhettinger Feb 19, 2023
22e1a96
Show math.isclose() for comparing inexact values
rhettinger Feb 19, 2023
cb1f78a
Add doctests throughout
rhettinger Feb 19, 2023
e9e959a
Add a more useful example of round() for comparisons
rhettinger Feb 19, 2023
8f02dc5
Shorter example
rhettinger Feb 19, 2023
d8bcc4c
Fix doctests: Missing import and counterfactual example.
rhettinger Feb 19, 2023
cd8abc5
Compare sum() and fsum() with straight addition
rhettinger Feb 19, 2023
d6a6b6b
Add section author
rhettinger Feb 19, 2023
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Shorter example
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@rhettinger
rhettinger committed Feb 19, 2023
commit 8f02dc507c46b4fa5759ea1811394823aaf14e62
17 changes: 8 additions & 9 deletions Doc/tutorial/floatingpoint.rst
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Expand Up @@ -238,15 +238,14 @@ each other out leaving a final sum near zero:

.. doctest::

>>> arr = [-125546.2071591587, 0.04336622547760194, 18741774.60535662,
... 57.207123035704896, 454267277684011.1, -0.04815896904694777,
... -18741774.600527752, -454267277558522.1]
>>> float(sum(map(Fraction, arr))) # Exact summation with single rounding
5.777552047891987e-12
>>> math.fsum(arr) # Single rounding
5.777552047891987e-12
>>> sum(arr) # Multiple roundings in extended precision
5.777545108998083e-12
>>> arr = [-0.10430216751806065, -266310978.67179024, 143401161448607.16,
... -143401161400469.7, 266262841.31058735, -0.003244936839808227]
>>> float(sum(map(Fraction, arr))) # Exact summation with single rounding
8.042173697819788e-13
>>> math.fsum(arr) # Single rounding
8.042173697819788e-13
>>> sum(arr) # Multiple roundings in extended precision
8.042178034628478e-13


.. _tut-fp-error:
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