12: Iteration in Python

Try it:

Below you’ll see some example python code that contains a shopping list

Press Ctrl + Enter  to run the code.

This code creates a list called farm and adds three strings to that list: "cat", "dog" and "mouse"

Line 4 iterates through each string in the list using the variable animal to keep track of which animal the current iteration is working with. For example, animal stores "cat" the first time line 5 runs but then animal stores "dog" on the next iteration of line 5 and "mouse" on the final iteration of line 5.

Challenges:

Start by running the code.

1. Change the cat to a pig
   

   When the code first runs you should see:

   Old McDonald had a farm E-I-E-I-O
   And on that farm he had a cat E-I-E-I-O
   Old McDonald had a farm E-I-E-I-O
   And on that farm he had a dog E-I-E-I-O
   Old McDonald had a farm E-I-E-I-O
   And on that farm he had a mouse E-I-E-I-O

   Change line 2 so that you see this when the code runs instead:

   Old McDonald had a farm E-I-E-I-O
   And on that farm he had a pig E-I-E-I-O
   Old McDonald had a farm E-I-E-I-O
   And on that farm he had a dog E-I-E-I-O
   Old McDonald had a farm E-I-E-I-O
   And on that farm he had a mouse E-I-E-I-O

2. Add a zebra to the farm
   

   Add a new string inside the list on line 2 

3. Repeat the whole song 5 times
   

   It might be helpful to look back at the theory page for this. You’ll need to choose which lines of code you want to repeat 5 times then indent them all (select and press tab) then write for i in range(5): above them.

On the next page you’ll get some code with both syntax and logic errors

KPRIDE

KPRIDE stands for Keywords, Predict, Run, Investigate, Debug and Extend and it’s a way of helping you explore and understand python code. Click on the image below for a set of KPRIDE activities for this python skill.

Page 1: Intro

Page 2: The theory: learn what you need to know as fast as possible.

Page 3: Try it: try out and adapt some working python code snippets.

Page 4: Debug it: Learn how to find and fix common mistakes.

Page 5: Extend it: Choose a project idea to use your newfound python skills.