Lesson 13 Notes: Gettin' the Gotchas (A Review)

• Plan Ahead
  • Plan before you code.
    • Create and write out "pseudocode"
    • Get structure planned before programming
  • Choose the best structure:
    • list or string?
    • Function or while loop?
  • Avoid obfuscational complexity
    Why make it messy when you can make it simple?
• Mutability
  • Lists can be changed without reassigning them.
    list = ["a", "b", "c"]
list.append("d")

  • Strings cannot be changed without reassigning
    text = "I Like Mommy"
text = string.upper(text)

• Values in Functions
  • If a function needs a variable not created inside the function, pass it in:
    word = raw_input("Enter a word: ")
def word_cap(word):
    print string.capitalize(word)
word_cap(word)

• Fruitful Functions
  • If your function needs to give a value back to the main program, give it a handle
    def find_lcm(num1,num2):
    index = 1
    while 1:
        mult1 = num1* index
        mult2 = num2*index
        if mult1 == mult2:
            return mult1
lcm = find_lcm(num1,num2)
• Recursive Alternative
  • Instead of recursing a function, use a while loop and "break" out of it:
    while 1:
    pwd = raw_input("Password: ")
    if pwd != "it's-a-secret":
        print "Incorrect. Entry denied."
    else:
        break

• Etcetera, Etcetera, Etcetera
  • Before submitting a program, make sure it runs without any traceback errors.
  • IDLE Tricks:
    • Mass Indent / De-dent
    • Mass Comment / Uncomment
• Tutor List
  • Got questions and teacher isn't helpful? Check out the official Python tutor email list.
  • http://mail.python.org/mailman/listinfo/tutor