5. Functions - LAC

Lecture notes

• Read Python Crash Course Chapter 8
• Cheat Sheet: functions, Cheat Sheet: functions BW,

Before class (code, output, mymath.py)

• Make a function with two arguments flavour and size. The function should print a message similar to this
  We will make a large pepperoni pizza
  Call the function once with positional arguments and once with keywords.
• Now add defaults to the function: the default flavour should be pepperoni, and the default size is large.
  Call it with one different value (your choice)
• Define a function called average which takes a list of numbers and returns their average.
  my_numbers = [10, 20, 30, 40, 50] print(f"The average of {my_numbers} is {average(my_numbers)}") > The average of [10, 20, 30, 40, 50] is 30.0
• Modify the average function to return None if the list is empty, and print a message like "The list is empty."
• Save the function in another file, called mymath.py.
  • Make sure it is properly styled with a docstring
  • Call it with an alias as av
  ⚠ Google Colab will not allow you to create a file locally or save it between sessions ⚠
  ⚠ So make the file on your computer and upload it! ⚠

  • You can use:
    • Notepad in Windows. Notepad should save plain text files by default.
    • WordPad in Windows. Use File → Save As... and select the option that allows you to save the file as a Text Document — rather than Rich Text Format (RTF), which is the default.
    • TextEdit on the Mac. Use the Make Plain Text command in the Format menu before saving the file.
  • Then in Colab
    • Click on the “Files” tab on the left-side menu. (Make sure it is the “Files tab” not the “File” Dropdown menu)
    • Click on the “Upload to Session Storage” button and select the file(s) you want to upload.

  ⚠ I will ask you to show me this file and function at the beginning of class ⚠
• Python comes with many modules built in, and you can download many, many more from the web (see the Python Package Index (PyPI)). We would normally use the built in statistics package to calculate the average (mean).
  from statistics import mean as av

Practical work (code, output)

• Write a function called print_items that takes any number of items and prints each one on a new line.
  # Example call print_items("apple", "banana", "cherry")
• Write a function called print_details that takes an arbitrary number of keyword arguments representing details about something and prints each key-value pair.
  # Example call print_details(name="Alice", age=25, city="New York")
• Write a function IsReduplicated that takes a word (in Malay) and returns True if it has been reduplicated and False otherwise. Ignore case. Assume a reduplicated word is formed by repeating the base word with a hyphen between them, such as buku-buku (books) from buku "book".
  # Example call IsReduplicated("orang-orang")
  Hint: use split(), with an argument, ...
• Write a function that takes a list of words, and returns a dictionary of each word that is reduplicated, and how many times. Use IsReduplicated to check the words.
  # Example call text = """Ini adalah Chi no Ike di dasar Neraka , tempat timbul-tenggelamnya Kandata bersama para pendosa lain . Dilihat dari sudut manapun tempat ini gelap pekat . Terkadang , dari balik kegelapan , samar-samar terlihat kilauan jaru-jarum dari Bukit Jarum yang mengerikan . Kengerian yang muncul tidak terperikan . Ditambah lagi suasananya yang senyap bagai dalam kuburan , seringali sayup-sayup hanya terdengar suara lenguhan nafas para pendosa . Orang-orang yang samapi jatuh ke tempat ini , begitu kelelahan oleh berbagai macam siksaan Neraka sampai-sampai tidak lagi punya tenaga untuk mengeluarkan rintihan derita . Karenanya , tentu sajasi maling besar Kandata pun sesenggukan di kubangan darah dalam kolam dan gelagapan persis seperti katak sekarat yang tidak bisa berbuat apa-apa . Ini orang-orang .""" # from https://arqu3fiq.blogspot.com/2007/12/kumo-no-ito.html redups=find_redup(text.split()) print(redups)
• Write a function called informal that takes a list of words and return a list of words with reduplicated words replaced by the informal version: e.g., word-word with word2.

After Class (code, output)

• Write a function count_vowels that takes a string and returns the number of vowels (a, e, i, o, u) in it.
  print(count_vowels("hello")) # Expected output: 2 print(count_vowels("Python")) # Expected output: 1
• Extend the function to work with Czech
  print(count_vowels("Válka")) # Expected output: 2 print(count_vowels("Krk")) # Expected output: 0 print(count_vowels("Ano")) # Expected output: 2
• ❂ In English, repeated words are often mistakes. Write a function repeats that takes a list of words and warns if there are any words that appear twice in a row and where the first one appears.
  repeats(['The', 'the', 'book', 'is', 'very', 'very', 'good']) # expect: # 'the' repeated in position 0 # 'very' repeated in position 4 repeats(["hello", "world", "hello"]) # expect Nothing
  Hint, use indices to compare word[x] with with word[x+1]
• ❂ Write a function called update_inventory that takes a dictionary representing current inventory and an arbitrary number of additional items. The function should add the new items to the inventory.
  # Example dictionary and function call current_inventory = {"apple": 2, "banana": 3} new_inventory = update_inventory(current_inventory, "apple", "banana", "cherry") print(new_inventory)

❂ A little bit harder, if you can't get it, study the answer

Summary

• You learned how to write functions and pass arguments to provide necessary information to functions.
• You learned to use positional and keyword arguments, and accept an arbitrary number of arguments.
• You saw functions that display output and those that return values.
• You learned how to use functions with lists, dictionaries, if statements, and while loops.
• You saw how to store functions in separate files called modules to simplify program files.
• You learned how to style your functions for well-structured and readable code.

Functions are import for the following reasons:

• Functions allow you to write blocks of code once and reuse them multiple times with a simple one-line call.
• Modifying a function affects every place where that function is called, making updates easy.
• Functions make programs easier to read, with good function names summarizing what each part does.
• Functions help you test and debug your code by isolating specific jobs, making it easier to verify function behavior.
• Testing functions separately gives you confidence that they will work correctly when called.

LAC: Language and the Computer Francis Bond.