Mailman 3 April 2021 - NumPy-Discussion

mixed mode arithmetic
by Neal Becker 11 Jul '23

11 Jul '23

I've been browsing the numpy source. I'm wondering about mixed-mode arithmetic on arrays. I believe the way numpy handles this is that it never does mixed arithmetic, but instead converts arrays to a common type. Arguably, that might be efficient for a mix of say, double and float. Maybe not. But for a mix of complex and a scalar type (say, CDouble * Double), it's clearly suboptimal in efficiency. So, do I understand this correctly? If so, is that something we should improve?

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Invalid value encoutered : how to prevent numpy.where to do this?
by Eric Emsellem 18 Feb '23

18 Feb '23

Dear all, I have a code using lots of "numpy.where" to make some constrained calculations as in: data = arange(10) result = np.where(data == 0, 0., 1./data) # or data1 = arange(10) data2 = arange(10)+1.0 result = np.where(data1 > data2, np.sqrt(data1-data2), np.sqrt(data2-data2)) which then produces warnings like: /usr/bin/ipython:1: RuntimeWarning: invalid value encountered in sqrt or for the first example: /usr/bin/ipython:1: RuntimeWarning: divide by zero encountered in divide How do I avoid these messages to appear? I know that I could in principle use numpy.seterr. However, I do NOT want to remove these warnings for other potential divide/multiply/sqrt etc errors. Only when I am using a "where", to in fact avoid such warnings! Note that the warnings only happen once, but since I am going to release that code, I would like to avoid the user to get such messages which are irrelevant here (because I am testing, with the where, when NOT to divide by zero or take a sqrt of a negative number). thanks! Eric

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Documentation Team meeting - Monday June 8th
by Melissa Mendonça 04 Dec '22

04 Dec '22

Hi all! A reminder that on Monday, June 8, we have another documentation team meeting at 3PM UTC**. If you wish to join on Zoom, you need to use this link https://zoom.us/j/420005230 Here's the permanent hackmd document with the meeting notes: https://hackmd.io/oB_boakvRqKR-_2jRV-Qjg <https://www.google.com/url?q=https%3A%2F%2Fhackmd.io%2FoB_boakvRqKR-_2jRV-Q…> Hope to see you around (especially if you want to introduce yourself or discuss ideas for Google Season of Docs). ** You can click this link to get the correct time at your timezone: https://www.timeanddate.com/worldclock/fixedtime.html?msg=NumPy+Documentati… - Melissa

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[Feature Request] Add alias of np.concatenate as np.concat
by Iordanis Fostiropoulos 10 May '22

10 May '22

In regard to Feature Request: https://github.com/numpy/numpy/issues/16469 It was suggested to sent to the mailing list. I think I can make a strong point as to why the support for this naming convention would make sense. Such as it would follow other frameworks that often work alongside numpy such as tensorflow. For backward compatibility, it can simply be an alias to np.concatenate I often convert portions of code from tf to np, it is as simple as changing the base module from tf to np. e.g. np.expand_dims -> tf.expand_dims. This is done either in debugging (e.g. converting tf to np without eager execution to debug portion of the code), or during prototyping, e.g. develop in numpy and convert in tf. I find myself more than at one occasion to getting syntax errors because of this particular function np.concatenate. It is unnecessarily long. I imagine there are more people that also run into the same problems. Pandas uses concat (torch on the other extreme uses simply cat, which I don't think is as descriptive).

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Re: [Numpy-discussion] example reading binary Fortran file
by Neil Martinsen-Burrell 22 Jul '21

22 Jul '21

David Froger <david.froger.info <at> gmail.com> writes: > Hy,My question is about reading Fortran binary file (oh no this question > again...) I've posted this before, but I finally got it cleaned up for the Cookbook. For this purpose I use a subclass of file that has methods for reading unformatted Fortran data. See http://www.scipy.org/Cookbook/FortranIO/FortranFile. I'd gladly see this in numpy or scipy somewhere, but I'm not sure where it belongs. > program makeArray > implicit none > integer,parameter:: nx=10,ny=20 > real(4),dimension(nx,ny):: ux,uy,p > integer :: i,j > open(11,file='uxuyp.bin',form='unformatted') > do i = 1,nx > do j = 1,ny > ux(i,j) = real(i*j) > uy(i,j) = real(i)/real(j) > p (i,j) = real(i) + real(j) > enddo > enddo > write(11) ux,uy > write(11) p > close(11) > end program makeArray When I run the above program compiled with gfortran on my Intel Mac, I can read it back with:: >>> import numpy as np >>> from fortranfile import FortranFile >>> f=FortranFile('uxuyp.bin', endian='<') >>> uxuy = f.readReals(prec='f') # 'f' for default reals >>> len(uxuy) 400 >>> ux = np.array(uxuy[:200]).reshape((20,10)).T >>> uy = np.array(uxuy[200:]).reshape((20,10)).T >>> p = f.readReals('f').reshape((20,10)).T >>> ux array([[ 1., 2., 3., 4., 5., 6., 7., 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20.], [ 2., 4., 6., 8., 10., 12., 14., 16., 18., 20., 22., 24., 26., 28., 30., 32., 34., 36., 38., 40.], [ 3., 6., 9., 12., 15., 18., 21., 24., 27., 30., 33., 36., 39., 42., 45., 48., 51., 54., 57., 60.], [ 4., 8., 12., 16., 20., 24., 28., 32., 36., 40., 44., 48., 52., 56., 60., 64., 68., 72., 76., 80.], [ 5., 10., 15., 20., 25., 30., 35., 40., 45., 50., 55., 60., 65., 70., 75., 80., 85., 90., 95., 100.], [ 6., 12., 18., 24., 30., 36., 42., 48., 54., 60., 66., 72., 78., 84., 90., 96., 102., 108., 114., 120.], [ 7.,Proxy-Connection: keep-alive Cache-Control: max-age=0 14., 21., 28., 35., 42., 49., 56., 63., 70., 77., 84., 91., 98., 105., 112., 119., 126., 133., 140.], [ 8., 16., 24., 32., 40., 48., 56., 64., 72., 80., 88., 96., 104., 112., 120., 128., 136., 144., 152., 160.], [ 9., 18., 27., 36., 45., 54., 63., 72., 81., 90., 99., 108., 117., 126., 135., 144., 153., 162., 171., 180.], [ 10., 20., 30., 40., 50., 60., 70., 80., 90., 100., 110., 120., 130., 140., 150., 160., 170., 180., 190., 200.]]) >>> uy array([[ 1. , 0.5 , 0.33333334, 0.25 , 0.2 , 0.16666667, 0.14285715, 0.125 , 0.11111111, 0.1 , 0.09090909, 0.08333334, 0.07692308, 0.07142857, 0.06666667, 0.0625 , 0.05882353, 0.05555556, 0.05263158, 0.05 ], [ 2. , 1. , 0.66666669, 0.5 , 0.40000001, 0.33333334, 0.2857143 , 0.25 , 0.22222222, 0.2 , 0.18181819, 0.16666667, 0.15384616, 0.14285715, 0.13333334, 0.125 , 0.11764706, 0.11111111, 0.10526316, 0.1 ], [ 3. , 1.5 , 1. , 0.75 , 0.60000002, 0.5 , 0.42857143, 0.375 , 0.33333334, 0.30000001, 0.27272728, 0.25 , 0.23076923, 0.21428572, 0.2 , 0.1875 , 0.17647059, 0.16666667, 0.15789473, 0.15000001], [ 4. , 2. , 1.33333337, 1. , 0.80000001, 0.66666669, 0.5714286 , 0.5 , 0.44444445, 0.40000001, 0.36363637, 0.33333334, 0.30769232, 0.2857143 , 0.26666668, 0.25 , 0.23529412, 0.22222222, 0.21052632, 0.2 ], [ 5. , 2.5 , 1.66666663, 1.25 , 1. , 0.83333331, 0.71428573, 0.625 , 0.55555558, 0.5 , 0.45454547, 0.41666666, 0.38461539, 0.35714287, 0.33333334, 0.3125 , 0.29411766, 0.27777779, 0.2631579 , 0.25 ], [ 6. , 3. , 2. , 1.5 , 1.20000005, 1. , 0.85714287, 0.75 , 0.66666669, 0.60000002, 0.54545456, 0.5 , 0.46153846, 0.42857143, 0.40000001, 0.375 , 0.35294119, 0.33333334, 0.31578946, 0.30000001], [ 7. , 3.5 , 2.33333325, 1.75 , 1.39999998, 1.16666663, 1. , 0.875 , 0.77777779, 0.69999999, 0.63636363, 0.58333331, 0.53846157, 0.5 , 0.46666667, 0.4375 , 0.41176471, 0.3888889 , 0.36842105, 0.34999999], [ 8. , 4. , 2.66666675, 2. , 1.60000002, 1.33333337, 1.14285719, 1. , 0.8888889 , 0.80000001, 0.72727275, 0.66666669, 0.61538464, 0.5714286 , 0.53333336, 0.5 , 0.47058824, 0.44444445, 0.42105263, 0.40000001], [ 9. , 4.5 , 3. , 2.25 , 1.79999995, 1.5 , 1.28571427, 1.125 , 1. , 0.89999998, 0.81818181, 0.75 , 0.69230771, 0.64285713, 0.60000002, 0.5625 , 0.52941179, 0.5 , 0.47368422, 0.44999999], [ 10. , 5. , 3.33333325, 2.5 , 2. , 1.66666663, 1.42857146, 1.25 , 1.11111116, 1. , 0.90909094, 0.83333331, 0.76923078, 0.71428573, 0.66666669, 0.625 , 0.58823532, 0.55555558, 0.52631581, 0.5 ]]) >>> p array([[ 2., 3., 4., 5., 6., 7., 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21.], [ 3., 4., 5., 6., 7., 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22.], [ 4., 5., 6., 7., 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23.], [ 5., 6., 7., 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24.], [ 6., 7., 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25.], [ 7., 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25., 26.], [ 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25., 26., 27.], [ 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25., 26., 27., 28.], [ 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25., 26., 27., 28., 29.], [ 11., 12., 13., 14., 15., 16., 17., 18., 19., 20., 21., 22., 23., 24., 25., 26., 27., 28., 29., 30.]]) Note that you have to provide the shape information for ux and uy because fortran writes them together as a stream of 400 numbers. -Neil

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Add smallest_normal and smallest_subnormal attributes to finfo
by Stephannie Jiménez Gacha 19 Jul '21

19 Jul '21

Good afternoon, Given the discussions happened in the Data API consortium when looking into the attributes of `finfo` used in the wild, we found that `tiny` is used regularly but in a good amount of cases not for its intended purpose but rather as "just give me a small number". Following this we are proposing the addition of `smallest_normal` and `smallest_subnormal` attributes. Personally, I think that the `tiny` name is a little bit odd and misleading, so it will be great to leave that as an alias but have a clear name in this class. Right now the PR: https://github.com/numpy/numpy/pull/18536 has all the changes and all the values added were checked against IEEE-754 standard. One of the main concerns is the support of subnormal numbers in certain architectures, where the values can't be calculated accurately. Given the state of the discussion, we don't know if the best alternative is to not add the `smallest_subnormal` attribute and just add the `smallest_number` attribute as an alias to `tiny`. We open this to discussion to see what way we can go in order to get this PR merged. *Stephannie Jimenez Gacha*Software developer *Quansight* | Your Data Experts w: www.quansight.com e: sgacha(a)quansight.com <https://www.linkedin.com/company/quansight> <https://twitter.com/quansightai>

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NEP 42 status
by Lee Johnston 12 May '21

12 May '21

Is the work on NEP 42 custom DTypes far enough along to experiment with? Lee

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GSoD 2021 - Statement of Interest
by Mahesh S 10 May '21

10 May '21

Hello, I am Mahesh from India. I am interested in doing Google Season of Docs with NumPy on the project HIGH-LEVEL RESTRUCTURING AND END-USER FOCUS - NumPy I have past experience in documentation writing with WordPress and have completed *Google Summer of Code 2018 *with KDE. I have been an open source enthusiast and contributor since 2017.My past experience with coding ,code documentation , understanding code bases ,will help achieve this task without much input from your end. I have about four years experience working with Open-Source and currently working as a *Quality Assurance specialis*t . I have delivered technical talks at international conferences (KDE-Akademy) and was *mentor of Google Code-In* also. All these makes me the best candidate for the project. I am attaching a brief proposal for the work along with this mail. A more in-depth A more in depth proposal with timelines , all planned strategies , document structures will be submitted after more discussion with the mentors and community. I am ready to start the work as soon as possible and will be able work 7 to 9 hours per day including weekends. I strongly wish to be part of the NumPy community even after the project. Hope to hear from you soon -- Thank you Mahesh S Nair

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Fwd: PhD position in the Netherlands; solar energy/Python
by Dr. Mark Alexander Mikofski PhD 30 Apr '21

30 Apr '21

Hello, sharing a PhD position opening at Utrecht in Netherlands. Read more below... ---------- Forwarded message --------- From: Mark Mikofski <bwanamarko(a)gmail.com> Date: Fri, Apr 30, 2021, 12:29 PM Subject: Fwd: PhD position in the Netherlands; solar energy/Python To: Mark Alexander Mikofski <mikofski(a)berkeley.edu> PhD positions with Wilfried van Sark at Utrecht Netherlands ---------- Forwarded message --------- From: abedw...(a)googlemail.com <abedwayyad(a)googlemail.com> Date: Monday, April 19, 2021 at 9:22:00 AM UTC-7 Subject: PhD position in the Netherlands; solar energy/Python To: pvlib-python <pvlib-python(a)googlegroups.com> Hello all, I did my MSc with Wilfried at Utrecht (the Netherlands). He's a truly wonderful mentor with an amazing and broad grasp of the knowledge. 10/10 would recommend doing a PhD there if you or someone you know would like to develop solar forecasting models. They are looking for pythonistas. All the best, Abed ---------- Forwarded message --------- From: dr. Wilfried van Sark - W.G.J.H....(a)uu.nl <blackboar...(a)uu.nl> Date: Wed, Apr 14, 2021 at 4:11 AM Subject: Master Energy Science: Looking for PhD/junior researchers To: Dear all, I am looking for talented and motivated junior researchers that would be interested to work in two projects: 1) ROBUST project: this recently granted project is focused on investigating options for flexibility in local electricity grids by using vehicle-to-grid technology in neighborhoods in Utrecht and Arnhem. We require experience with data analysis and simulation using Python. In this project we collaborate with WeDriveSolar and TUDelft. We have funding for at least 44 months available. 2) PVObs and SolFaSi projects. Both projects deal with photovoltaic performance and forecasting. The PVObs project aims to create a large database of PV systems in the Netherlands in order to assess their performance and from that determine with better accuracy the contribution of PV to the national electricity demand. Parnters in this project are CBS and SunData. The SolFaSi project aims to develop PV forecasting at high time and spatial resolutions using all-sky imagers (aka cloud cameras). We will install three cameras at the UU campus and one at KNMI. This network allows to construct a moving shadow field over the campus. This should be correlated with the power generation of the 4000+ PV panels at campus buildings. We require experience with (big) data analysis and simulation using Python. We have funding for 24 months available. If you are interested, or if you know someone who may be interested, please send me a mail at w.g.j.h....(a)uu.nl best regards Wilfried

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NumPy Tutorials
by Melissa Mendonça 30 Apr '21

30 Apr '21

Hello, all! Recently, we added a link to NumPy Tutorials to our main page ( https://numpy.org/numpy-tutorials) This set of tutorials has been built with the collaboration of a few contributors, who have put effort and dedication into them. Some of this content was generated as part of last year's Google Season of Docs program, with authors kubedoc and Ryan Cooper. These tutorials are meant to be not only about NumPy, but about using NumPy to solve concrete problems, which means more flexibility in terms of content and dependencies for executing them. They are also executable as Jupyter Notebooks, and contributors can submit their content as notebooks. This hopefully means a lower barrier of entry for some people, and allows us to have interactive materials online (with Binder). We also have a dedicated tutorials section in our main documentation, which should serve a different purpose (for example, focusing on concepts and operations specific to NumPy). The Documentation Team is growing and we would be delighted to have your help. If you have comments, suggestions for improvements or other content, please open an issue or PR in the https://github.com/numpy/numpy-tutorials repo. Special thanks to Ross Barnowski who has also put a lot of work into this new site. Cheers! Melissa

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