IDEs

Now we will switch to Spyder. Spyder is an Integrated Development Environment, or IDE, aimed at Python. It is well suited to developing longer, more modular programs. To start it, return to the Anaconda Navigator and click on its tile. It may take a while to open (watch the lower left of the Navigator). Once it starts, you will see a layout with an editor pane on the left, an explorer pane at the top right, and an iPython console on the lower right. This arrangement can be customized but we will use the default for our examples. Type code into the editor. The explorer window can show files, variable values, and other useful information. The iPython console is a frontend to the Python interpreter itself. It is comparable to a cell in JupyterLab.

If you are using Python 2.7, add the line from future import print_function immediately after the triple-quoted section.

If you type

print("Hello World")

into the editor pane, it is a script and you must run it in order for the command to be carried out. Click the green arrow to run the current script.

You can also type commands directly into the iPython console. Just as with JupyterLab, if you type an expression its value will be printed.

In  [1]: x=5
In  [2]: y=7
In  [3]: x+y
Out [3]: 12

This is not the case for expressions typed into the editor pane.

x=5
y=7
x+y

We will see nothing if we run this as a script. You must add a print command to see any output as well as running the script.

In the iPython console we can also use up-down arrow keys to screen in our commands, and right-left arrows to edit them.

Example

We can see some of these features in action by creating a simple plot. after the green triple quotes in an “untitled” editor tab, type

import matplotlib.pylab as plt

First we see a yellow triangle, indicating a syntax problem – in this case, plt is imported but not used. We ignore this warning since we will be using it. As we type

x=plt.

we see the editor show us our choices from the pylab package. We can select one or keep typing. We type

x=plt.linsp

to narrow it down further. That leads us to

x=plt.linspace

The editor then pops up a box with the arguments required by linspace. Finally we type inside the parentheses

-1.*plt.pi,plt.pi,100

for a final result of

x=plt.linspace(-1.*plt.pi,plt.pi,100)

After this we type

y=plt.sin(x)
plt.plot(x,y)

You must save a file before you can run it. Go the File menu, Save As, and name it sine.py Use the project folder you created earlier. When we run this code, we see the plot appear embedded in the iPython window. We can right-click on the image to bring up a menu that allows us to save the plot.

The Variable Explorer

The Variable Explorer allows us to show the values of variables in our programs. It is particularly helpful for looking at a group of values (an array). We can change the number of decimal places printed by clicking Format and typing in an expression of the %3f for three decimal places. The Variable Explorer also includes icons for saving, refreshing, or importing data to our workspace.

To clear all values in the workspace, type at the iPython console

%reset

Now re-run your sine-plotting code and observe how the variables acquire values.

Change sin to cos and rerun your script.

Other IDEs

Other popular IDEs for Python include the “fremium” PyCharm. The “Community” (free) edition is adequate for most casual programmer’s needs. Some organizations, such as the UVA Computer Science Department, hold licenses that students or employees can access.

VSCode is another IDE. It is multilanguage but can be easily extended to support Python.

Resources

Spyder documentation is here.