$$ \newcommand{\Oof}[1]{\mathcal{O}(#1)} \newcommand{\F}{\boldsymbol{F}} \newcommand{\J}{\boldsymbol{J}} \newcommand{\x}{\boldsymbol{x}} \renewcommand{\c}{\boldsymbol{c}} $$




The SageMathCloud and Wakari web services

You can avoid installing Python on your machine completely by using a web service that allows you to write and run Python programs. Computational science projects will normally require some kind of visualization and associated graphics packages, which is not possible unless the service offers IPython notebooks. There are two excellent web services with notebooks: SageMathCloud at https://cloud.sagemath.com/ and Wakari at https://www.wakari.io/wakari. At both sites you must create an account before you can write notebooks in the web browser and download them to your own computer.

Basic intro to SageMathCloud

Sign in, click on New Project, give a title to your project and decide whether it should be private or public, click on the project when it appears in the browser, and click on Create or Import a File, Worksheet, Terminal or Directory.... If your Python program needs graphics, you need to choose IPython Notebook, otherwise you can choose File. Write the name of the file above the row of buttons. Assuming we do not need any graphics, we create a plain Python file, say with name py1.py. By clicking File you are brought to a browser window with a text editor where you can write Python code. Write some code and click Save. To run the program, click on the plus icon (New), choose Terminal, and you have a plain Unix terminal window where you can write python py1.py to run the program. Tabs over the terminal (or editor) window make it easy to jump between the editor and the terminal. To download the file, click on Files, point on the relevant line with the file, and a download icon appears to the very right. The IPython notebook option works much in the same way, see the section Writing IPython notebooks.

Basic intro to Wakari

After having logged in at the wakari.io site, you automatically enter an IPython notebook with a short introduction to how the notebook can be used. Click on the New Notebook button to start a new notebook. Wakari enables creating and editing plain Python files too: click on the Add file icon in pane to the left, fill in the program name, and you enter an editor where you can write a program. Pressing Execute launches an IPython session in a terminal window, where you can run the program by run prog.py if prog.py is the name of the program. To download the file, select test2.py in the left pane and click on the Download file icon.

There is a pull-down menu where you can choose what type of terminal window you want: a plain Unix shell, an IPython shell, or an IPython shell with Matplotlib for plotting. Using the latter, you can run plain Python programs or commands with graphics. Just choose the type of terminal and click on +Tab to make a new terminal window of the chosen type.

Installing your own Python packages

Both SageMathCloud and Wakari let you install your own Python packages. To install any package packagename available at PyPi, run

pip install --user packagename

To install the SciTools package, which is useful when working with this book, run the command

pip install --user -e \