Learning Python

Appendix C. Solutions to Exercises

This appendix contains solutions to the exercises that appear at the end of each chapter.

Chapter 1

1. Interaction. Assuming your Python is configured properly, you should participate in an interaction that looks something like this:

   % python
   copyright information lines...
   >>> "Hello World!"
   'Hello World!'
   >>>                       # <Ctrl-D or Ctrl-Z to exit>

2. Programs. Here’s what your code (i.e., module) file and shell interactions should look like:

   % cat module1.py
   print 'Hello module world!'
   
   % python module1.py
   Hello module world!

3. Modules. The following interaction listing illustrates running a module file by importing it. Remember that you need to reload it to run again without stopping and restarting the interpreter. The bit about moving the file to a different directory and importing it again is a trick question: if Python generates a module1.pyc file in the original directory, it uses that when you import the module, even if the source code file (.py) has been moved to a directory not on Python’s search path. The .pyc file is written automatically if Python has access to the source file’s directory and contains the compiled bytecode version of a module. We look at how this works in more detail in Chapter 5.

   % python
   >>> import module1
   Hello module world!
   >>>

4. Scripts. Assuming your platform supports the #! trick, your solution will look like the following (though your #! line may need to list another path on your machine):

   % cat module1.py #!/usr/local/bin/python (or ...