Python IDLE

by K. Yue

1. Python IDLE

• Python IDLE is bundled in the Python distribution. There is no need for separate installation.
• IDLE can be regarded as a very simple Integrated Development Environment (IDE). It is used in this class.

• A short IDLE tutorial: https://www.youtube.com/watch?v=WIlQukiXs-E. (a little dated)
• https://realpython.com/python-idle/ is a very good tutorial on IDLE. However, it contains many topics not needed in this class.

2. Running IDLE shell as interpreter

• When you start IDLE, a shell window appears.
• IDLE shell is an interactive interpreter with REPL (Read-Evaluate-Print loop)
  • Read a Python statement, single-lined or multiple-lined.
  • Evaluate or execute the statement.
  • Print the result of execution of the statement.
• A shell contains the collection of Python code the user entered interactively.

2.1 Logging a shell session

• Logging is a crucial practice and habit in software development.
• Logging tracks program behavior and problems, enables debugging, supports performance analysis, supports auditing, monitors security and informs users, administrators, and developers.
• IDLE shell session can be logged by saving it in a file.

Shell Menu

• Two buttons you may use:
  1. Restart shell: start a new shell session.
  2. Interrupt Execution: stop the execution (in case you get into an infinite loop)

3. Python program file editing and execution

• Shell includes a text editor.
• One can open an existing Python program file, or create anew Python program file.

• The file editor has many features.

• Some features you may use:
  • Use the options menu to show line number.
  • Set and clear breakpoints for debugging.
  • Run the program by using Run->Run Module.

4. Debugging in IDLE

• A good tutorial in IDLE: https://www.cs.uky.edu/~keen/help/debug-tutorial/debug.html. Contain more than needed in the class.
• To debug a Python program:
  1. Open the Python program using IDLE Shell: File -> Open.
  2. Turn on the Shell debugger: Go->Debugger
  3. Run the program in the editor using Run->Run Module.
  4. Use the debugger window.
• Some basics:
  • Use the go button in the debugger window to execute.
  • Set and clear breakpoint in the editor.
  • Examine the locals window in the debugger.

When the debugger window is started, in the example below, the locals window shows values of local variables.

An example of using breakpoints:

• Useful debugger options:
  • step: one step at a time, including lower level function calls.
  • over: one step at a time, not including lower level function calls. Probably more useful than 'step'.
  • go: executes full theprogram.