2. Introducing and Working with Lists.

Lecture notes

• Read Python Crash Course Chapters 3 and 4
• List is a collection which is ordered and changeable. Allows duplicate members.
  myvocab = ["kore", "sore", "are"]
vocab = list()
vocab.append('word')
vocab.insert('another')
• Tuple is a collection which is ordered and unchangeable. Allows duplicate members.
  myvocab = ("kore", "sore", "are")
myques = ("dore", ) ## need the comma to distinguish from a function
• Cheat Sheet: list, Cheat Sheet: list BW
• Two very useful methods:
  • string → list: 'some things'.split()
  • list → string: ', '.join(['some', 'things'])

Further reading

• Getting Started with Python (Lists)
  Slides from Object-Oriented Programming in Python (Goldwasser and Letscher)
• Formatting Strings from Rowan Nicholls' Introduction to Python

Before class (code, output)

• Make a list that includes at least three people you’d like to invite to dinner. Then use your list to print a message to each person, inviting them to dinner. Try to choose interesting people (like in Van Loon's Lives)
• You just found a bigger dinner table, so now more space is available. Think of three more guests to invite to dinner.
  • Start with your program from the first exercise and add a print() call to the end of your program, informing people that you found a bigger table.
  • Use insert() to add one new guest to the beginning of your list.
  • Use insert() to add one new guest to the middle of your list.
  • Use append() to add one new guest to the end of your list.
• Use len() to print a message indicating the number of people you’re inviting to dinner.
• Use a for loop to print a message to each of your guests, and then write a general message to all of them outside of the list
• Do the same thing, but printing the names in alphabetical order
• Use list comprehension, len() and max() to say how long the longest name is

Problems adapted from PCC 3.4, 3.6, 3.9

Practical work (code, output)

• You can multiply a string, and you get n copies of the string!
• Try out this code:

  for i in range(1, 7):
      print('*' * i)
  for i in range(7, 13):
      print('*' * (12 -i))
  

  • Make a square
  • Make a pyramid
  • Try something else!
• Here are some examples of Korean Onomatopoeia:

      data = [
      # Korean Onomatopoeia
      ("개굴개굴", "gaegul-gaegul", "Ribbit (frog sound)"),
      ("멍멍", "meong-meong", "Woof (dog barking)"),
      ("야옹", "ya-ong", "Meow (cat sound)"),
      ("딸랑딸랑", "ddal-lang-ddal-lang", "Jingle (bell sound)"),
      ]
  

  • Make a new list having just the words (not the transliteration or gloss)
  • Sort this list.

Further work (code, output)

• Make a list of the numbers from one to one million, and then use min() and max() to make sure your list actually starts at one and ends at one million. Finally, use sum() to sum them.
• Using the list of guests from your before class problem, divide them into two using list comprehension: list1 should have the odd numbered guests and list2 should have the even numbered guests.
• Use a list comprehension to make a list of tuples! The first element of each tuple should be a number from 1-9 and the second element should be its square: [(1,1), (2,4), (3,9), ...]. Then use a for loop and an fstring to print
  The square of 1 is 1, The square of 2 is 4, ...
• Produce a reversed list of Japanese numerals from "十" to "一" using a range and a for loop. Use the following tuple of Japanese numerals:

  japanese_numerals = ("一", "二", "三", "四", "五", "六", "七", "八", "九", "十")

  • Example Output:

    ['十', '九', '八', '七', '六', '五', '四', '三', '二', '一']

Some problems adapted from PCC 4-5.

Summary

• you can access items in lists: list1[0], list1[-1], ...
• you can access sublists using slices: list1[first:last:step]
• list comprehensions are powerful: [fun(w) for w in V if p(w)]
• you can add to and remove things from lists
• you can sort lists
• you can reverse lists
• there are many things you can do to lists

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LAC: Language and the Computer Francis Bond.