This unit is about, "putting it all together". We are going to start by looking at debugging using paper techniques and the built in debugger.

Debugging with IDLE

Sometimes, your code just doesn't do do what you want it to do.

Odd behaviours include:

• Blocks of code that are skipped
• Loops that don't run
• Loops that don't run as many times as you wanted them to
• Arrays that you can't read or write to properly

How do you trouble shoot this?

A simple quick method is to use a print().

for i in range(0,5):

    #do something cool, 5 times

How could I know if the loop actually ran 5 times?

I could use a simple print(i). By including that print() in the loop, I can see my variable change:

for i in range(0,5):

    # do something cool, 5 times

    print(i)

When I was sure that the loop was doing what I wanted, I would remove that line of code.

Debugging with print statements is a quick and common solution in all programming languages, but is there a better way?

IDEs (Integrated Development Environment) like IDLE have built in debuggers that help the programmer to trace code.