10.7 Exercises

Most of the topics of this chapter are not really good topics for exercises without first covering the frameworks they cover. A couple of things can be done with the knowledge you already have, however:

Faking the Web . You may not have a web server running, which makes using formletter.py and FormEditor.py difficult, since they use data generated by the CGI script. As an exercise, write a program that creates files with the same properties as those created by the CGI script.
Cleaning up . There's a serious problem with the formletter.py program: namely, if, as we mention, it's run nightly, any complaint is going to cause a letter to be printed. That will happen every night, since there is no mechanism for indicating that a letter has been generated and that no more letters need be generated regarding that specific complaint. Fix this problem.
Adding parametric plotting to grapher . py . Modify grapher.py to allow the user to specify expressions that return both x and y values, instead of the current "just y" solution. For example, the user should be able to write in the Expression widget: sin(x/3.1),cos(x/6.15) (note the comma: this is a tuple!) and get a picture like that shown in Figure 10.8.

Figure 10.8. Output of Exercise 3