Writing a simple Plot Function


See Getting Started.

Activate the Conda workshop enviroment:

$ source activate workshop


We are going to write a simple plot function in Python using matplotlib and cartopy.


  • You will learn how to install packages with Conda.
  • You will learn the basic usage of the netCDF, matplotlib and cartopy Python libraries.

Run the plotter

Go to the plotter tutorial source:

$ cd ~/birdhouse-workshop/tutorials/01_plotter

Try the plotter Python module:

$ python plotter.py
Traceback (most recent call last):
File "plotter.py", line 1, in <module>
  import matplotlib.pylab as plt
ModuleNotFoundError: No module named 'matplotlib'

Oops, something is missing … please install the matplotlib package via Conda:

# Let's see what is available
$ conda search -c conda-forge matplotlib

# ... and install it from the conda-forge channel
$ conda install -c conda-forge matplotlib

Conda will show you a list of packages, which are going to be installed. Have a look at this list and answer with y or just press enter.

The following NEW packages will be INSTALLED:

matplotlib:       2.0.2-py36_2  conda-forge

Proceed ([y]/n)?

We should check now the plotter.py source code. Open the plotter.py in your favorite editor, some people like vim:

$ vim plotter.py

Besides matplotlib there is another import for netCDF4:

from netCDF4 import Dataset

Let us install netcdf4:

# same procedure as above ...
$ conda search -c conda-forge netcdf4
$ conda install -c conda-forge netcdf4

So, we should now be ready to run the plotter:

$ python plotter.py
Plotting ../data/air.mon.ltm.nc ...
Plot written to plot.png

A plot was generated. Open it in your favorite image viewer. On Ubuntu/LinuxMint you can try Eye of Gnome, on macOS just say open:

$ eog plot.png  # on Ubuntu use Eye of Gnome
$ open plot.png # on macOS

The image should look like the following:



Open the plotter.py and implement the following features:

  • add a colorbar
  • add a background map with coastlines
  • use a PlateCarree map projection

You will need an additional Python package, cartopy, which you can install with conda. This package is available on the conda-forge channel. You need to provide an option with the conda channel:

$ conda install -c conda-forge mypackage

Read the code and comments carefully to make this work.

The final result should look like this: