meta data for this page

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision		Previous revision
software:python [2017/02/23 08:24] – external edit 127.0.0.1software:python [2021/12/14 20:36] (current) – [Pandas/Geopandas] christian
Line 1: Line 1:
 Useful links and snippets regarding Python and Jupyter notebooks Useful links and snippets regarding Python and Jupyter notebooks
 +
 +====== Modules ======
 +
 +  * The uncompromising Python code formatter [[https://black.readthedocs.io/en/stable/]] and on Github: [[https://github.com/psf/black]]
 +
  
 ===== iPython/Jupyter resources ===== ===== iPython/Jupyter resources =====
  
-* [[https://www.packtpub.com/books/content/basics-jupyter-notebook-and-python|Basics of Jupyter notebooks (on packtpub.com)]] +  * [[https://www.packtpub.com/books/content/basics-jupyter-notebook-and-python|Basics of Jupyter notebooks (on packtpub.com)]] 
-* [[http://maxmelnick.com/2016/04/19/python-beginner-tips-and-tricks.html|Max Melnick's Jupyter Python Notebook Keyboard Shortcuts and Text Snippets for Beginners]] +  * [[http://maxmelnick.com/2016/04/19/python-beginner-tips-and-tricks.html|Max Melnick's Jupyter Python Notebook Keyboard Shortcuts and Text Snippets for Beginners]] 
-* [[http://jupyter.readthedocs.io/en/latest/index.html|Jupyter notebooks documentation]]+  * [[http://jupyter.readthedocs.io/en/latest/index.html|Jupyter notebooks documentation]] 
 +  * [[http://matplotlib.org/examples/color/colormaps_reference.html|Matplotlib colormaps]] and [[https://stackoverflow.com/questions/3373256/set-colorbar-range-in-matplotlib| how to normalise a colormap]] 
 +  * [[https://maxmasnick.com/projects/scipy-tips/|Max Masnick's Dat science Python snippets]] 
 +  * [[https://realpython.com/python-matplotlib-guide/|MatPlotLib guide]] 
 + 
 + 
 + 
 + 
 +===== Quick and dirty ===== 
 + 
 +  * [[http://stackoverflow.com/questions/16566069/url-decode-utf-8-in-python#16566128|Decode URLs using Python]]  
 +  * <code python> 
 +# py3 
 +from urllib import parse 
 +parse.unquote("""TheURLString""") 
 +# or in py2.7 
 +import urllib 
 +urllib.unquote("theURL").decode('utf8') 
 +</code> 
 +  * Translate coordinate reference system from ''*.prj'' files to proj4-Syntax as required by QGIS using the gdal python module (via [[https://gis.stackexchange.com/questions/7608/shapefile-prj-to-postgis-srid-lookup-table/7615#7615|GIS on Stackexchange]]: 
 +  * <code python> 
 +import sys 
 +from osgeo import osr 
 +prjtxt = """PROJCS["your_crs",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["the_prj"],PARAMETER["Central_Meridian",0.0],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Latitude_Of_Origin",0.0],PARAMETER["Standard_Parallel_1",-10],PARAMETER["Standard_Parallel_2",50],UNIT["Meter",1.0],AUTHORITY["me",123456]]""" 
 +srs = osr.SpatialReference() 
 +print 'Proj4 is: %s' % srs.ExportToProj4() 
 +Proj4 is: <string with proj4 parameters follows> 
 +</code> 
 + 
 + 
 +==== Pandas/Geopandas ==== 
 + 
 +  * Invert a single column of a Pandas Dataframe: ''df.col2 = df.col2.values[::-1]'' [[https://stackoverflow.com/questions/46244235/invert-a-single-column-in-a-dataframe|via StackOverflow]] 
 +  * Joining multiple overlapping column names from multiple dataframes: ''pd.concat(data, axis=1)'' [[https://stackoverflow.com/questions/13003769/joining-multiple-dataframes-with-pandas-with-overlapping-column-names|via StackOverflow]] 
 +  * Cross-section indexing of a multi-indexed dataframe - using levels: ''concatdf.xs('MIndexValue', level='MIndexName')'' - [[http://pandas-docs.github.io/pandas-docs-travis/user_guide/advanced.html#advanced-xs|via Pandas documentation]] and [[https://stackoverflow.com/questions/24435788/using-loc-with-a-multiindex-in-pandas#24436783|StackOverflow]] 
 +  * [[https://stackoverflow.com/questions/53645882/pandas-merging-101|Pandas merging 101]] on StackOverflow. 
 +  * Going from a regular dataframe to geopandas data frame: ''gdf = geopandas.GeoDataFrame(df, geometry=geopandas.points_from_xy(df.Longitude, df.Latitude))'' -- [[https://geopandas.readthedocs.io/en/latest/gallery/create_geopandas_from_pandas.html|via Geopandas doc]] 
 +  * Obtaining unique values for Multi-index levels: ''concatdf.index.unique(level=1)'' 
 +  * Drop a level of multi-index into a column: ''df.reset_index(level=[...])'' - via [[https://stackoverflow.com/questions/20110170/turn-pandas-multi-index-into-column|StackOverflow]] 
 +  * Generating a column with conditional values based on an existing column [[https://datagy.io/pandas-conditional-column/|via datagy.io]]: ''myDict = { 'a': 1, 'b': 2, 'c': 3}'', ''df[newCol] = df[oldCol].map( myDict )''
  
  
 ===== Stuff related to modules ===== ===== Stuff related to modules =====
  
-* [[osgeo.ogr]]+  * [[https://gdal.org/python/osgeo.ogr-module.html|osgeo.ogr]] 
 +  * [[http://effbot.org/zone/import-confusion.htm|Importing modules - effbot's import confusion]] 
 +  * Installing a new module in Enthough Canopy Light's distro on Windows: I managed to install the [[https://pypi.python.org/pypi/dbf|DBF module]] by navigating to the unzipped content downloaded in the Python console. Then I just typed ''%run setup.py install'' and the compiled module is then installed in the Canopy's ''User\Lib\site-packages'' directory. Easy.
  
-* Installing a new module in Enthough Canopy Light's distro on Windows: I managed to install the [[https://pypi.python.org/pypi/dbf|DBF module]] by navigating to the unzipped content downloaded in the Python console. Then I just typed ''%run setup.py install'' and the compiled module is then installed in the Canopy's ''User\Lib\site-packages'' directory. Easy.+{{tag> Python Programming Jupyter iPython notebooks pandas}}
  
-{{tag> Python Programming Jupyter iPython notebooks}}