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other:python:jyp_steps [2016/06/27 15:31] jypeter [Basemap] Added note about basemap->cartopy transition, and started cartopy section |
other:python:jyp_steps [2018/08/23 09:54] jypeter Added the 'extra numpy' section, with lots of info about indexing |
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You can start using python by reading the {{:other:python:python_intro_ipsl_oct2013_v2.pdf|Bien démarrer avec python}} tutorial that was used during a 2013 IPSL python class: | You can start using python by reading the {{:other:python:python_intro_ipsl_oct2013_v2.pdf|Bien démarrer avec python}} tutorial that was used during a 2013 IPSL python class: | ||
* this tutorial is in French (my apologies for the lack of translation, but it should be easy to understand) | * this tutorial is in French (my apologies for the lack of translation, but it should be easy to understand) | ||
+ | * If you have too much trouble understanding this French Tutorial, you can read the first 6 chapters of the **Tutorial** in [[#the_official_python_documentation|the official Python documentation]] and chapters 1.2.1 to 1.2.5 in the [[#scipy_lecture_notes|Scipy Lecture Notes]]. Once you have read these, you can try to read the French tutorial again | ||
* it's an introduction to python (and programming) for the climate scientist: after reading this tutorial, you should be able to do most of the things you usually do in a shell script | * it's an introduction to python (and programming) for the climate scientist: after reading this tutorial, you should be able to do most of the things you usually do in a shell script | ||
* python types, tests, loops, reading a text file | * python types, tests, loops, reading a text file | ||
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- [[https://docs.scipy.org/doc/numpy-dev/user/numpy-for-matlab-users.html|Numpy for Matlab users]] | - [[https://docs.scipy.org/doc/numpy-dev/user/numpy-for-matlab-users.html|Numpy for Matlab users]] | ||
- [[http://mathesaurus.sourceforge.net/matlab-numpy.html|NumPy for MATLAB users]] (nice, but does not seem to be maintained any more) | - [[http://mathesaurus.sourceforge.net/matlab-numpy.html|NumPy for MATLAB users]] (nice, but does not seem to be maintained any more) | ||
- | - read the [[https://docs.scipy.org/doc/numpy-dev/user/quickstart.html|Quickstart tutorial]] | + | - read the really nice [[https://docs.scipy.org/doc/numpy/user/quickstart.html|numpy Quickstart tutorial]] |
- have a quick look at the full documentation to know where things are | - have a quick look at the full documentation to know where things are | ||
- Numpy User Guide | - Numpy User Guide | ||
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[20, 21, -1, -1, 24, 25, 26, 27, 28, 29]]) | [20, 21, -1, -1, 24, 25, 26, 27, 28, 29]]) | ||
</code></note> | </code></note> | ||
+ | |||
+ | ==== Extra numpy information ==== | ||
+ | |||
+ | * More information about array indexing: | ||
+ | * [[https://docs.scipy.org/doc/numpy/user/basics.indexing.html|Indexing]] (//index arrays//, //boolean index arrays//, //np.newaxis//, //Ellipsis//, //variable numbers of indices//, ...) | ||
+ | * [[https://docs.scipy.org/doc/numpy/user/quickstart.html#fancy-indexing-and-index-tricks|Fancy indexing]] and [[https://docs.scipy.org/doc/numpy/user/quickstart.html#the-ix-function|the ix_() function]] | ||
+ | * [[https://docs.scipy.org/doc/numpy/reference/arrays.indexing.html|Indexing (in the numpy reference manual)]] | ||
+ | * [[https://docs.scipy.org/doc/numpy/reference/routines.indexing.html#routines-indexing|Indexing routines]] | ||
+ | * [[https://docs.scipy.org/doc/numpy/user/misc.html#ieee-754-floating-point-special-values|Dealing with special numerical values]] (//Nan//, //inf//) | ||
+ | * If you know that your data has missing values, it is cleaner and safer to handle them with masks | ||
+ | * [[https://docs.scipy.org/doc/numpy/user/misc.html#how-numpy-handles-numerical-exceptions|Handling numerical exceptions]] | ||
===== cdms2 and netCDF4 ===== | ===== cdms2 and netCDF4 ===== | ||
- | There is a good chance that your input array data will come from a file in the [[http://www.unidata.ucar.edu/software/netcdf/|NetCDF]] format. Depending on which [[other:python:starting#some_python_distributions|python distribution]] you are using, you can use the //cdms2// or or //netCDF4// modules to read the data. | + | There is a good chance that your input array data will come from a file in the [[other:newppl:starting#netcdf_and_file_formats|NetCDF format]]. |
- | Note: the NetCDF file format is self-documented, and the metadata of climate date files often follows the [[http://cfconventions.org/|CF (Climate and Forecast) Metadata Conventions]] | + | Depending on which [[other:python:starting#some_python_distributions|python distribution]] you are using, you can use the //cdms2// or or //netCDF4// modules to read the data. |
==== cdms2 ==== | ==== cdms2 ==== | ||
- | Summary: cdms2 can read/write netCDF files (and read //grads// dat+ctl files) and provides a higher level interface than netCDF4. Unfortunately, cdms2 is only available in the UV-CDAT distribution, and distributions where somebody has installed some version of //cdat-lite//. When you can use cdms2, you also have access to //cdtime//, that is very useful for handling time axis data. | + | Summary: cdms2 can read/write netCDF files (and read //grads// dat+ctl files) and provides a higher level interface than netCDF4. cdms2 is available in the [[other:python:starting#uv-cdat|UV-CDAT distribution]], and can theoretically be installed independently of UV-CDAT (e.g. it will be installed when you install [[https://cmor.llnl.gov/mydoc_cmor3_conda/|CMOR in conda)]]. When you can use cdms2, you also have access to //cdtime//, that is very useful for handling time axis data. |
How to get started: | How to get started: | ||
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- the tutorial is in French (soooorry!) | - the tutorial is in French (soooorry!) | ||
- you have to replace //cdms// with **cdms2**, and //MV// with **MV2** (sooorry about that, the tutorial was written when CDAT was based on //Numeric// instead of //numpy// to handle array data) | - you have to replace //cdms// with **cdms2**, and //MV// with **MV2** (sooorry about that, the tutorial was written when CDAT was based on //Numeric// instead of //numpy// to handle array data) | ||
- | - read the [[http://uv-cdat.llnl.gov/documentation/cdms/cdms.html|official cdms documentation]] | + | - read the [[http://cdms.readthedocs.io/en/docstanya/index.html|official cdms documentation]] (link may change) |
- | - ask questions and get answers on the [[http://uvcdat.askbot.com/questions/|UV-CDAT askbot]] | + | |
==== netCDF4 ==== | ==== netCDF4 ==== | ||
- | Summary: netCDF4 can read/write netCDF files and is available in most python distributions | + | Summary: //netCDF4 can read/write netCDF files and is available in most python distributions// |
Where: [[http://unidata.github.io/netcdf4-python/]] | Where: [[http://unidata.github.io/netcdf4-python/]] | ||
+ | ===== CDAT-related resources ===== | ||
+ | |||
+ | Some links, in case they can't be found easily on the [[https://uv-cdat.llnl.gov|UV-CDAT]] web site... | ||
+ | |||
+ | * [[https://uv-cdat.llnl.gov/tutorials.html|Tutorials in ipython notebooks]] | ||
+ | * [[http://cdat-vcs.readthedocs.io/en/latest/|VCS: Visualization Control System]] | ||
+ | * [[https://github.com/CDAT/vcs/issues/238|Colormaps in vcs examples]] | ||
+ | * [[https://github.com/CDAT/cdat-site/blob/master/eztemplate.md|EzTemplate Documentation]] | ||
===== Matplotlib ===== | ===== Matplotlib ===== | ||
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Where: [[http://matplotlib.org|Matplotlib web site]] | Where: [[http://matplotlib.org|Matplotlib web site]] | ||
- | The documentation is good, but not always easy to use. A good way to start with matplotlib is to: | + | Help on //stack overflow//: [[https://stackoverflow.com/questions/tagged/matplotlib|matplotlib help]] |
+ | |||
+ | The documentation is good, but not always easy to use. <wrap hi>A good way to start with matplotlib</wrap> is to: | ||
- Look at the [[http://matplotlib.org/gallery.html|matplotlib gallery]] to get an idea of all you can do with matplotlib. Later, when you need to plot something, come back to the gallery to find some examples that are close to what you need and click on them to get the sources | - Look at the [[http://matplotlib.org/gallery.html|matplotlib gallery]] to get an idea of all you can do with matplotlib. Later, when you need to plot something, come back to the gallery to find some examples that are close to what you need and click on them to get the sources | ||
- Use the free hints provided by JY! | - Use the free hints provided by JY! | ||
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- sometimes the results of the python/matplolib commands are displayed directly, sometimes not. It depends if you are in [[http://matplotlib.org/faq/usage_faq.html#what-is-interactive-mode|interactive or non-interactive]] mode | - sometimes the results of the python/matplolib commands are displayed directly, sometimes not. It depends if you are in [[http://matplotlib.org/faq/usage_faq.html#what-is-interactive-mode|interactive or non-interactive]] mode | ||
- the documentation may mention [[http://matplotlib.org/faq/usage_faq.html#what-is-a-backend|backends]]. What?? Basically, you use python commands to create a plot, and the backend is the //thing// that will render your plot on the screen or in a file (png, pdf, etc...) | - the documentation may mention [[http://matplotlib.org/faq/usage_faq.html#what-is-a-backend|backends]]. What?? Basically, you use python commands to create a plot, and the backend is the //thing// that will render your plot on the screen or in a file (png, pdf, etc...) | ||
+ | - if you don't see a part of what you have plotted, maybe it's hidden behind other elements! Use the [[https://matplotlib.org/examples/pylab_examples/zorder_demo.html|zorder parameter]] to explicitly specify the plotting order/layers | ||
- Read the [[http://www.labri.fr/perso/nrougier/teaching/matplotlib/|Matplotlib tutorial by Nicolas Rougier]] | - Read the [[http://www.labri.fr/perso/nrougier/teaching/matplotlib/|Matplotlib tutorial by Nicolas Rougier]] | ||
- Download the [[http://matplotlib.org/contents.html|pdf version of the manual]]. **Do not print** the 2800+ pages of the manual! Read the beginner's guide (Chapter //FIVE// of //Part II//) and have a super quick look at the table of contents of the whole document. | - Download the [[http://matplotlib.org/contents.html|pdf version of the manual]]. **Do not print** the 2800+ pages of the manual! Read the beginner's guide (Chapter //FIVE// of //Part II//) and have a super quick look at the table of contents of the whole document. | ||
+ | |||
+ | ===== Graphics related resources ===== | ||
+ | |||
+ | * [[http://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1003833|Ten Simple Rules for Better Figures]] | ||
+ | * [[http://seaborn.pydata.org/|Seaborn]] is a library for making attractive and informative statistical graphics in Python, built on top of matplotlib | ||
+ | * See also: [[https://www.datacamp.com/community/tutorials/seaborn-python-tutorial| | ||
+ | Python Seaborn Tutorial For Beginners]] | ||
+ | * Working with colors | ||
+ | * [[https://matplotlib.org/users/colormaps.html|Choosing colormaps]] | ||
+ | * [[https://matplotlib.org/cmocean/|Beautiful colormaps for oceanography: cmocean]] | ||
+ | * [[http://colorbrewer2.org|ColorBrewer 2.0]] is a tool that can help you understand, and experiment with //sequential//, //diverging// and //qualitative// colormaps | ||
+ | |||
===== Basemap ===== | ===== Basemap ===== | ||
- | <note warning>It seems that basemap is going to slowly phased out, in favor of [[#cartopy]]\\ More information in this [[https://github.com/matplotlib/basemap/issues/267|basemap github issue]] | + | <note warning>Basemap is going to be slowly phased out, in favor of [[#cartopy]]\\ More information in this: |
+ | * [[https://github.com/SciTools/cartopy/issues/920|cartopy github issue]] | ||
+ | * [[https://github.com/matplotlib/basemap/issues/267|basemap github issue]] | ||
</note> | </note> | ||
- | Summary: Basemap is an extension of Matplotlib that you can use for plotting maps, using different projections | + | Summary: //Basemap is an extension of Matplotlib that you can use for plotting maps, using different projections// |
Where: [[http://matplotlib.org/basemap/|Basemap web site]] | Where: [[http://matplotlib.org/basemap/|Basemap web site]] | ||
+ | |||
+ | Help on //stack overflow//: [[https://stackoverflow.com/questions/tagged/matplotlib-basemap|basemap help]] | ||
How to use basemap? | How to use basemap? | ||
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- look at the [[http://matplotlib.org/basemap/api/basemap_api.html#module-mpl_toolkits.basemap|detailed official documentation]] | - look at the [[http://matplotlib.org/basemap/api/basemap_api.html#module-mpl_toolkits.basemap|detailed official documentation]] | ||
- | ===== Cartopy ===== | + | ===== Cartopy + Iris ===== |
- | Summary: //Cartopy makes use of the powerful PROJ.4, numpy and shapely libraries and has a simple and intuitive drawing interface to matplotlib for creating publication quality maps// | + | Summary: //Cartopy is a Python package for advanced map generation with a simple matplotlib interface// and //Iris is a Python package for analysing and visualising meteorological and oceanographic data sets// |
+ | |||
+ | Where: [[http://scitools.org.uk/cartopy/docs/latest/|Cartopy]] and [[http://scitools.org.uk/iris/index.html|Iris]] web sites | ||
+ | |||
+ | Examples: | ||
+ | * [[http://scitools.org.uk/cartopy/docs/latest/gallery.html|Gallery on the Cartopy web site]] | ||
+ | * [[http://scitools.org.uk/iris/docs/latest/gallery.html|Gallery on the Iris web site]] | ||
+ | * [[http://scitools.org.uk/iris/docs/latest/examples/index.html|Examples on the Iris web site]] | ||
+ | |||
+ | Help on //stack overflow//: [[https://stackoverflow.com/questions/tagged/cartopy|cartopy help]] | ||
+ | |||
+ | ===== Maps and projections resources ===== | ||
+ | |||
+ | ==== About projections ==== | ||
+ | |||
+ | * [[https://egsc.usgs.gov/isb//pubs/MapProjections/projections.html|Map projections from USGS poster]] | ||
+ | * [[https://pubs.usgs.gov/pp/1395/report.pdf|Map projections - A working manual (USGS)]] | ||
+ | |||
+ | ==== Libraries ==== | ||
+ | |||
+ | * Projections in vcs | ||
+ | * [[http://matplotlib.org/basemap/users/mapsetup.html|Projections in basemap]] | ||
+ | * [[https://scitools.org.uk/cartopy/docs/latest/crs/projections.html|Projections in cartopy]] | ||
+ | |||
+ | |||
+ | ===== 3D resources ===== | ||
+ | |||
+ | * [[https://ipyvolume.readthedocs.io/en/latest/|Ipyvolume]] | ||
+ | * [[https://zulko.wordpress.com/2012/09/29/animate-your-3d-plots-with-pythons-matplotlib/|Animate your 3D plots with Python’s Matplotlib]] | ||
+ | * [[https://stackoverflow.com/questions/26796997/how-to-get-vertical-z-axis-in-3d-surface-plot-of-matplotlib|How to get vertical Z axis in 3D surface plot of Matplotlib?]] | ||
+ | |||
+ | ===== Data file formats ===== | ||
+ | |||
+ | We list here some resources about non-NetCDF data formats that can be useful | ||
+ | |||
+ | ==== json files ==== | ||
+ | |||
+ | More and more applications use //json files// as configuration files or as a mean to use text files to exchange data (through serialization/deserialization ). | ||
+ | |||
+ | //json// files look basically like a **list of (nested) python dictionaries** that would have been dumped to a text file | ||
+ | |||
+ | * [[https://docs.python.org/2/library/json.html|json module]] documentation | ||
+ | * [[https://realpython.com/python-json/|Working With JSON Data in Python]] tutorial | ||
+ | * example script: ''/home/users/jypeter/CDAT/Progs/Devel/beaugendre/nc2json.py'' | ||
+ | * A compact (not easy to read...) //json// file can be pretty-printed with\\ ''cat file.json | python -m json.tool | less'' | ||
+ | |||
+ | ==== LiPD files ==== | ||
+ | |||
+ | Resources for //Linked PaleoData//: | ||
+ | * [[http://linked.earth/projects/lipd/|LiPD]] | ||
+ | * [[https://doi.org/10.5194/cp-12-1093-2016|Technical note: The Linked Paleo Data framework – | ||
+ | a common tongue for paleoclimatology]] @ GMD | ||
+ | * [[https://github.com/nickmckay/LiPD-utilities|LiPD-utilities]] @ github | ||
+ | |||
+ | ==== BagIt files ==== | ||
+ | |||
+ | //BagIt//, a set of hierarchical file layout conventions for storage and transfer of arbitrary digital content. | ||
+ | |||
+ | * [[https://tools.ietf.org/html/draft-kunze-bagit-16|The BagIt File Packaging Format]] | ||
+ | * [[https://github.com/LibraryOfCongress/bagger|Bagger]] (BagIt GUI) | ||
+ | * [[https://github.com/LibraryOfCongress/bagit-python|bagit-python]] | ||
+ | ===== Pandas ===== | ||
+ | |||
+ | Summary: //pandas is a library providing high-performance, easy-to-use data structures and data analysis tools// | ||
+ | |||
+ | Where: [[http://pandas.pydata.org|Pandas web site]] | ||
+ | |||
+ | JYP's comment: pandas is supposed to be quite good for loading, processing and plotting time series, without writing custom code. You should at least have a quick look at: | ||
+ | * The [[http://www.scipy-lectures.org/packages/statistics/index.html|Statistics in Python]] tutorial that combines Pandas, [[http://statsmodels.sourceforge.net/|Statsmodels]] and [[http://seaborn.pydata.org/|Seaborn]] | ||
+ | * the cheat sheet on the [[https://www.enthought.com/services/training/pandas-mastery-workshop/|Enthought workshops advertising page]] | ||
+ | * the cheat sheet on the [[https://github.com/pandas-dev/pandas/tree/master/doc/cheatsheet|github Pandas doc page]] | ||
- | Where: [[http://scitools.org.uk/cartopy/docs/latest/|Cartopy web site]] | ||
===== Scipy Lecture Notes ===== | ===== Scipy Lecture Notes ===== | ||
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Where: [[http://www.scipy-lectures.org/_downloads/ScipyLectures-simple.pdf|pdf]] - [[http://www.scipy-lectures.org/|html]] | Where: [[http://www.scipy-lectures.org/_downloads/ScipyLectures-simple.pdf|pdf]] - [[http://www.scipy-lectures.org/|html]] | ||
- | This is a really nice document that is regularly updated and used for the [[https://www.euroscipy.org/|EuroScipy]] tutorials. You will learn more things about python, numpy and matplotlib, debugging and optimizing scripts, and also learn about using python for statistics, image processing, machine learning, washing dishes (this is just to check if you have read this page), etc... | + | This is **a really nice and useful document** that is regularly updated and used for the [[https://www.euroscipy.org/|EuroScipy]] tutorials. You will learn more things about python, numpy and matplotlib, debugging and optimizing scripts, and also learn about using python for statistics, image processing, machine learning, washing dishes (this is just to check if you have read this page), etc... |
===== Quick Reference ===== | ===== Quick Reference ===== | ||
* The nice and convenient Python 2.7 Quick Reference: [[http://rgruet.free.fr/PQR27/PQR2.7_printing_a4.pdf|pdf]] - [[http://rgruet.free.fr/PQR27/PQR2.7.html|html]] | * The nice and convenient Python 2.7 Quick Reference: [[http://rgruet.free.fr/PQR27/PQR2.7_printing_a4.pdf|pdf]] - [[http://rgruet.free.fr/PQR27/PQR2.7.html|html]] | ||
+ | * A possibly more [[http://iysik.com/PQR2.7/PQR2.7.html|up-date-version]] | ||
+ | |||
+ | * Python 3 [[https://perso.limsi.fr/pointal/python:abrege|Quick reference]] and [[https://perso.limsi.fr/pointal/python:memento|Cheat sheet]] | ||
===== Some good coding tips ===== | ===== Some good coding tips ===== | ||
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Depending on the distribution, the editor and the programming environment you use, you may have access to a graphical version of the debugger. UV-CDAT users can use ''pydebug my_script.py'' | Depending on the distribution, the editor and the programming environment you use, you may have access to a graphical version of the debugger. UV-CDAT users can use ''pydebug my_script.py'' | ||
+ | |||
+ | ===== Using a Python IDE ===== | ||
+ | |||
+ | **IDE** = //Integrated Development Environment// | ||
+ | |||
+ | There are lots of ways to use Python and develop scripts, from using a lightweight approach (your favorite text editor with builtin python syntax highlighting, e.g. **emacs** and ''python -i myscript.py'') to a full-fledged IDE. You'll find below some IDE related links | ||
+ | |||
+ | * [[https://www.datacamp.com/community/tutorials/data-science-python-ide|Top 5 Python IDEs For Data Science]] | ||
+ | * [[http://noeticforce.com/best-python-ide-for-programmers-windows-and-mac|Python IDE: The10 Best IDEs for Python Programmers]] | ||
+ | * [[https://wiki.python.org/moin/IntegratedDevelopmentEnvironments]] | ||
+ | |||
+ | ==== Spyder ==== | ||
+ | |||
+ | * [[https://github.com/spyder-ide/spyder|Home page]] | ||
+ | * [[http://pythonhosted.org/spyder/|Documentation]] | ||
+ | |||
===== Improving the performance of your code ===== | ===== Improving the performance of your code ===== |