Python Practice

[dolsysmith]

Ideas for Practice Session 1

Constraints for the Scrabble exercises:

• Have to look at one letter at a time
• Can use pen/paper to keep track of anything you want

Palindrome problem

• Use Scrabble tiles to let participants work through the logic of the problem by hand
• Scaffold with Parsons' Problems for folks who don't have a firm grasp of Python syntax

Run-length encoding

• Skip

Grouping data

• By hand with Scrabble tiles: create counts of consonants and vowels
• Parson Problems for scaffolding

[dolsysmith]

Lesson Plan

Preparation

• Handout on paper with rules
• Scrabble tiles: each set should consist of multiple letters, multiple instances of the same letter, though not every letter need have the same number of instance. But each set should contain a fair number of "repeats."
• If attendance allows, participants can work in groups.

Outline

1. Define palindrome; discuss as example of computational structure (something defined by a strict procedure, an algorithm).
2. Each group/participants (g/p) creates a palindrome. You don't have to use all your tiles. Your palindrome doesn't have to be a word.
3. Share and discuss results. What cases can we identify?
   • Even number of letters.
   • Odd number of letters.
   • Single letter (edge case).
4. Define the (computational) problem: Is a given sequence a palindrome?
   • A sequence will consist of at least one letter/tile.
   • The program should return a "true" value if the sequence is a palindrome, regardless of how many letters it contains. Otherwise, it should return a "false" value.
5. Each g/p creates a "program": a list of logical instructions. The following rules (handout) should guide your process:
   • You can use any number of variables.
   • A variable can hold single letters, sequences of letters, or numbers.
   • A variable can also be null, e.g., empty, if it holds no value.
   • You can modify variables:
     • replace one letter or number with another;
     • insert a letter into a sequence, either at the beginning or the end;
     • do any math with numbers you like.
   • You can compare two variables, testing for equality, greater than, or less than.
   • Two sequences are the same if they have the same letters in the same order.
   • You can find the length of a sequence, the result of which operation will be a number.
   • You can move backwards and forwards through a sequence, but only one letter at a time.
   • You can keep track of where you are in a sequence using a variable to record either the current letter or its numeric position relative to the beginning of the sequence.
   • You can do any of the above operations conditionally, that is, in response to whether a particular comparison between variables is "true" or "false."
6. Before g/p's start working on the exercise above, it might be useful to demonstrate what is meant by variable as well as by the last three rules. For example, model a program to identify if a letter appears twice in a row in the sequence, using two variables, one for the current letter, one for the last letter, with loop and conditional.
7. G/p's can write their programs either as a list of instructions or as a flow chart. Demonstrate the above example with a flow chart.
8. Each g/p exchanges their program with another g/p. Test the program:
   • Does it work?
   • Does it work for all cases?
   • Does it follow the rules?
   • How could it be improved?
9. Step through implementation in Python, using Google Colab.
10. If there is enough time, repeat the exercise for run-length encoding.
    • Run-length encoding is a method whereby, for a given sequence of letters, each subsequence of repeated letters is replaced by one instance of the repeated letter and a number indicating the length of the subsequence. So "aaabbcdddd" would be encoded as "a3b2c1d4", "abcd" would be encoded as "a1b1c1d1", and "a" would be encoded as "a1".
    • Write a program to produce the run-length encoding of a given sequence.