>>> spam = {'color': 'red', 'age': 42} >>> for k, v in spam.items(): ... print('Key: ' + k + ' Value: ' + str(v))
THis is better than for i in ,dict.items():
29 Matching Annotations
- Feb 2021
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automatetheboringstuff.com automatetheboringstuff.com
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Tic-Tac-Toe
Skip this and do it in next class or as hw Actually next class would be fun because we can play two player games and write tests
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list(spam.keys())
Can we use this for extra credit on the class work?
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dictionaries are not ordered
They are not guaranteed to be ordered, but this changes depeniding on language and versions
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>> spam = {'name': 'Zophie', 'age': 7} >>> spam['color'] Traceback (most recent call last): File "<pyshell#1>", line 1, in <module> spam['color'] KeyError: 'color'
what happens if you access a key that dies not exist. Kinda like out of bounds
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>>> eggs = {'name': 'Zophie', 'species': 'cat', 'age': '8'} >>> ham = {'species': 'cat', 'age': '8', 'name': 'Zophie'}
Let's make a new cat, Elliot tell us about yours Compare them they are not equal
And then let's make two chickens and see if they are equal. they are!
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>>> myCat['size'] 'fat' >>> 'My cat has ' + myCat['color'] + ' fur.'
How we get stuff and change it.
Let's change mood from hungry to hangry
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myCat = {'size': 'fat', 'color': 'gray', 'disposition': 'loud'}
Brad tell us about your cat and we'll make some keys and values
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➊ birthdays = {'Alice': 'Apr 1', 'Bob': 'Dec 12', 'Carol': 'Mar 4'} while True: print('Enter a name: (blank to quit)') name = input() if name == '': break ➋ if name in birthdays: ➌ print(birthdays[name] + ' is the birthday of ' + name) else: print('I do not have birthday information for ' + name) print('What is their birthday?') bday = input() ➍ birthdays[name] = bday print('Birthday database updated.')
Keys are unique. Can't have two Bobs
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allGuests = {'Alice': {'apples': 5, 'pretzels': 12}, 'Bob': {'ham sandwiches': 3, 'apples': 2}, 'Carol': {'cups': 3, 'apple pies': 1}} def totalBrought(guests, item): numBrought = 0 ➊ for k, v in guests.items(): ➋ numBrought = numBrought + v.get(item, 0) return numBrought print('Number of things being brought:') print(' - Apples ' + str(totalBrought(allGuests, 'apples'))) print(' - Cups ' + str(totalBrought(allGuests, 'cups'))) print(' - Cakes ' + str(totalBrought(allGuests, 'cakes'))) print(' - Ham Sandwiches ' + str(totalBrought(allGuests, 'ham sandwiches'))) print(' - Apple Pies ' + str(totalBrought(allGuests, 'apple pies')))
This is great but we can refactor this
Why do we hardcore the key when we print out? Can’t we loop over them and add them to a set?
Could we count the total number of items?
Could we count how many items each person brought?
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turn = 'X' for i in range(9): ➊ printBoard(theBoard) print('Turn for ' + turn + '. Move on which space?') ➋ move = input() ➌ theBoard[move] = turn ➍ if turn == 'X': turn = 'O' else: turn = 'X' printBoard(theBoard)
We’re gonna make a two player game
We have the dictionary Let’s make a function to put a x or o in a spot Pass the cell Id and the x or o in as arguments Then take the arguments and use to add to dict
So we can do that manually. But how do we handle turns? How about we have a turn counter and we check if it’s even or odd If it’s even we pass in d as argument. Else pass o
How do we know when to stop? Well we could go for 9 turns. Or let the users enter stop or I won Or we could check the board every time and tell the users
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theBoard = {'top-L': ' ', 'top-M': ' ', 'top-R': ' ', 'mid-L': ' ', 'mid-M': ' ', 'mid-R': ' ', 'low-L': ' ', 'low-M': ' ', 'low-R': ' '}
What should we call each cell?
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Let’s create a function to print the board dictionary onto the screen
How do they think the row should be printed?
Show them how you want a row to be printed
Then get one person to print a row
Then print the other rows
Then wrap it in a function
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If player X went first and chose the middle space, you could represent that board with this dictionary:
Get them to make a change
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- Jan 2021
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automatetheboringstuff.com automatetheboringstuff.com
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myPets = ['Zophie', 'Pooka', 'Fat-tail'] print('Enter a pet name:') name = input() if name not in myPets: print('I do not have a pet named ' + name) else: print(name + ' is my pet.')
Can find the largest
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>>> spam = ['cat', 'bat', 'rat', 'elephant'] >>> spam[1] = 'aardvark' >>> spam ['cat', 'aardvark', 'rat', 'elephant'] >>> spam[2] = spam[1] >>> spam ['cat', 'aardvark', 'aardvark', 'elephant'] >>> spam[-1] = 12345 >>> spam ['cat', 'aardvark', 'aardvark', 12345]
Maybe an example of ordering a list of names by alphabet or by length of name
Or just replacing someone in a queue.
Write with functions
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>>> spam = ['cat', 'bat', 'rat', 'elephant'] >>> spam[-1] 'elephant' >>> spam[-3] 'bat'
Good to get the top level domain of a url. or the last element to get the largest item if already sorted.
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tuples are different from lists is that tuples, like strings, are immutable
Immutability good for banking and to make sure anther program doesn't modify your vars
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the sort() method sorts the list in place
Maybe a good time to show them the docs
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>>> spam = ['cat', 'dog', 'bat'] >>> spam.insert(1, 'chicken') >>> spam ['cat', 'chicken', 'dog', 'bat']
Keep going with world records rankings
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>>> spam = ['hello', 'hi', 'howdy', 'heyas'] >>> spam.index('hello') 0 >>> spam.index('heyas') 3 >>> spam.index('howdy howdy howdy')
You want to find the position of a person in line to determine what place they are
So maybe world records, looking up their rankings
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>>> import random >>> people = ['Alice', 'Bob', 'Carol', 'David'] >>> random.shuffle(people) >>> people ['Carol', 'David', 'Alice', 'Bob'] >>> random.shuffle(people) >>> people ['Alice', 'David', 'Bob', 'Carol']
Maybe an example here could be make an iPod shuffle that doesn't complete
Get list of songs then random choice then delete the song then next random choice
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catNames = [] while True: print('Enter the name of cat ' + str(len(catNames) + 1) + ' (Or enter nothing to stop.):') name = input() if name == '': break catNames = catNames + [name] # list concatenation print('The cat names are:') for name in catNames: print(' ' + name)
Make list of names and then write function to sort them
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>>> spam = [['cat', 'bat'], [10, 20, 30, 40, 50]] >>> spam[0] ['cat', 'bat'] >>> spam[0][1] 'bat' >>> spam[1][4] 50
Good for mazes and games of checkers and tic tac toe
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>>> [1, 2, 3] [1, 2, 3] >>> ['cat', 'bat', 'rat', 'elephant'] ['cat', 'bat', 'rat', 'elephant'] >>> ['hello', 3.1415, True, None, 42]
Lists can all have same type or different types
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automatetheboringstuff.com automatetheboringstuff.com
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The Collatz Sequence
Fibonacci sequence? Recursion?
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def spam(divideBy): try: return 42 / divideBy except ZeroDivisionError: print('Error: Invalid argument.') print(spam(2)) print(spam(12)) print(spam(0)) print(spam(1))
Maybe show how expected argument is a number but we expected a string
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The call stack is how Python remembers where to return the execution after each function call. The call stack isn’t stored in a variable in your program; rather, Python handles it behind the scenes. When your program calls a function, Python creates a frame object on the top of the call stack. Frame objects store the line number of the original function call so that Python can remember where to return. If another function call is made, Python puts another frame object on the call stack above the other one.
Ask elliot
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meandering conversation with someon
Instead talk about the never ending things to do with Malcolm in the middle gif
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