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np.around and np.round supports complex numbers, but not np.trunc #17100

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xuhdev opened this issue Aug 18, 2020 · 3 comments
Open

np.around and np.round supports complex numbers, but not np.trunc #17100

xuhdev opened this issue Aug 18, 2020 · 3 comments
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00 - Bug 07 - Deprecation

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@xuhdev
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xuhdev commented Aug 18, 2020

Both around and round supports complex input, but not trunc. This looks a bit abnormal.

Reproducing code example:

In [1]: import numpy as np

In [2]: a=np.array([complex(1+1j)]*3)

In [3]: np.around(a)
Out[3]: array([1.+1.j, 1.+1.j, 1.+1.j])

In [4]: np.round(a)
Out[4]: array([1.+1.j, 1.+1.j, 1.+1.j])

In [5]: np.trunc(a)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-5-17494546b8df> in <module>
----> 1 np.trunc(a)

TypeError: ufunc 'trunc' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''

Numpy/Python version information:

1.19.1 3.7.3 (default, Jul 25 2020, 13:03:44) 
[GCC 8.3.0]
@eric-wieser
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eric-wieser commented Aug 20, 2020 •
edited by mattip
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I think this is deliberate. math.trunc doesn't support floatscomplex in python either:

In [14]: import math

In [15]: math.trunc(1.2+3.4j)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-15-25c8caeb25a5> in <module>
----> 1 math.trunc(1.2+3.4j)

TypeError: type complex doesn't define __trunc__ method

I don't expect numpy to change here unless python changes first.

Edit (mattip): float -> complex

@eric-wieser eric-wieser added 57 - Close? Issues which may be closable unless discussion continued and removed 57 - Close? Issues which may be closable unless discussion continued labels Aug 20, 2020
@eric-wieser
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eric-wieser commented Aug 20, 2020 •
edited
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Ah, I'm reading this backwards - if we care about consistency with python, we should deprecate round(complex):

In [18]: round(1+2j)
TypeError: type complex doesn't define __round__ method

So either we should add trunc, or deprecate round

@xuhdev
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xuhdev commented Aug 20, 2020

Why don't we propose Python to add these support? :-)

@kgryte kgryte mentioned this issue May 30, 2022
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