Index : Changing the index zoo_animals = ["pangolin", "cassowary", "sloth", "tiger"] # Last night our zoo's sloth brutally attacked #the poor tiger and ate it whole. # The ferocious sloth has been replaced by a friendly hyena. zoo_animals[2] = "hyena" # What shall fill the void left by our dear departed tiger? # Your code here! zoo_animals[2] = "hyena" # Changes "sloth" to "hyena" Late Arrivals & List the Length of the List suitcase = [] suitcase.append("sunglasses") # Your code here! suitcase.append("charger") suitcase.append("tshirts") suitcase.append("shorts") list_length = len(suitcase) # Set this to the length of suitcase print "There are %d items in the suitcase." % (list_length) print suitcase Output: There are 4 items in the suitcase. ['sunglasses', 'charger', 'tshirts', 'shorts'] None Example 2: letters = ['a', 'b', 'c'] letters.append('d') print len(letters) print letters List Slicing letters = ['a', 'b', 'c', 'd', 'e'] slice = letters[1:3] print slice print letters suitcase = ["sunglasses", "hat", "passport", "laptop", "suit", "shoes"] first = suitcase[0:2] # The first and second items (index zero and one) middle = suitcase[2:4] # Third and fourth items (index two and three) last = suitcase[4:6] # The last two items (index four and five) so first = [sunglasses, hat] (exclude position 2) middle=[passport, laptop] BUT, the suitcase list elements do not change! Slicing List & String my_list[:2] # Grabs the first two items my_list[3:] # Grabs the fourth through last items animals = "catdogfrog" cat = animals[:3] # The first three characters of animals dog = animals[3:6] # The fourth through sixth characters frog = animals[6:] # From the seventh character to the end Maintaining Order or Inserting index into a Specific Place animals = ["ant", "bat", "cat"] print animals.index("bat") Output : 1 animals.insert(1, "dog") print animals Output: ["ant", "dog", "bat", "cat"] Instructions: Use the .index(item) function to find the index of "duck". Assign that result to a variable called duck_index. Then .insert(index, item) the string "cobra" at that index. animals = ["aardvark", "badger", "duck", "emu", "fennec fox"] duck_index = animals.index("duck") # Use index() to find "duck" animals.insert(duck_index,"cobra") print animals # Observe what prints after the insert operation Output: ['aardvark', 'badger', 'cobra', 'duck', 'emu', 'fennec fox'] None For-Loop my_list = [1,9,3,8,5,7] for number in my_list: print 2*number # Your code here Output: 2, 18, 6, 16, 10, 14 for variable in list_name: # Do stuff! For-Loop Sorting & Appending animals = ["cat", "ant", "bat"] animals.sort() for animal in animals: print animal Output: "ant", "bat", "cat" Example 2: start_list = [5, 3, 1, 2, 4] square_list = [] for number in start_list: square_list.append(number**2)# Your code here! square_list.sort() print square_list Output: [1, 4, 9, 16, 25] Dictionary – Key d = {'key1' : 1, 'key2' : 2, 'key3' : 3} key 1, key 2, key 3 = key-value pairs # Assigning a dictionary with three key-value pairs to residents: residents = {'Puffin' : 104, 'Sloth' : 105, 'Burmese Python' : 106} print residents['Puffin'] # Prints Puffin's room number # Your code here! print residents['Sloth'] print residents['Burmese Python'] Output: 105 Output: 106 Dictionary – New Entries dict_name[new_key] = new_value An empty pair of curly braces {} is an empty dictionary, just like an empty pair of [] is an empty list. menu = {} # Empty dictionary menu['Chicken Alfredo'] = 14.50 # Adding new key-value pair print menu['Chicken Alfredo'] # Your code here: Add some dish-price pairs to menu! menu['Despacito']=19.2 menu['Dog']=20 menu['Cat']=30 print "There are " + str(len(menu)) + " items on the menu." print menu output: 14.5 There are 4 items on the menu. {'Chicken Alfredo': 14.5, 'Despacito': 19.2, 'Dog': 20, 'Cat': 30} None Dictionary – Deletion del dict_name[key_name] # key - animal_name : value - location zoo_animals = { 'Unicorn' : 'Cotton Candy House', 'Sloth' : 'Rainforest Exhibit', 'Bengal Tiger' : 'Jungle House', 'Atlantic Puffin' : 'Arctic Exhibit', 'Rockhopper Penguin' : 'Arctic Exhibit'} # A dictionary (or list) declaration may break across multiple lines # Removing the 'Unicorn' entry. (Unicorns are incredibly expensive.) del zoo_animals['Unicorn'] # Your code here! del zoo_animals['Sloth'] del zoo_animals['Bengal Tiger'] zoo_animals['Rockhopper Penguin']='Bird' print zoo_animals Output: {'Atlantic Puffin': 'Arctic Exhibit', 'Rockhopper Penguin': 'Bird'} None Remove stuff from a list beatles = ["john","paul","george","ringo","stuart"] beatles.remove("stuart") print beatles Output -- >> ["john","paul","george","ringo"] Alternative Algorithm: dict_name['list_key'].list_function() Complicating List & Dictionaries my_dict = { "fish": ["c", "a", "r", "p"], "cash": -4483, "luck": "good" } print my_dict["fish"][0] Output : c inventory = { 'gold' : 500, 'pouch' : ['flint', 'twine', 'gemstone'], # Assigned a new list to 'pouch' key 'backpack' : ['xylophone','dagger', 'bedroll','bread loaf'] } # Adding a key 'burlap bag' and assigning a list to it inventory['burlap bag'] = ['apple', 'small ruby', 'three-toed sloth'] # Sorting the list found under the key 'pouch' inventory['pouch'].sort() # Your code here inventory['pocket']=['seashell', 'strange berry', 'lint'] inventory['backpack'].sort() inventory['backpack'].remove('dagger') inventory['gold'] = inventory['gold']+50 print inventory Output: {'pocket': ['seashell', 'strange berry', 'lint'], 'backpack': ['bedroll', 'bread loaf', 'xylophone'], 'pouch': ['flint', 'gemstone', 'twine'], 'burlap bag': ['apple', 'small ruby', 'three-toed sloth'], 'gold': 550} None Re A Day at Supermarket Case: for loops allow us to iterate through all of the elements in a list from the left-most (or zeroth element) to the right-most element. A sample loop would be structured as follows: a = ["List of some sort”] for x in a: # Do something for every x for item in [1, 3, 21]: print item would print 1, then 3, and then 21 Example: names = ["Adam","Alex","Mariah","Martine","Columbus"] for name in names: print name # A simple dictionary d = {"foo" : "bar"} for key in d: print d[key] # prints "bar" webster = { "Aardvark" : "A star of a popular children's cartoon show.", "Baa" : "The sound a goat makes.", "Carpet": "Goes on the floor.", "Dab": "A small amount." } # Add your code below! for jargon in webster: print webster[jargon] Output: A star of a popular children's cartoon show. Goes on the floor. A small amount. The sound a goat makes. None *Note that the outcome will not come as order using this function. For-Loop with if-statement numbers = [1, 3, 4, 7] for number in numbers: if number > 6: print number print "We printed 7." a = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13] for number in a: if number%2==0: print number List + Function: def count_small(numbers): total = 0 for n in numbers: if n < 10: total = total + 1 return total lost = [4, 8, 15, 16, 23, 42] small = count_small(lost) print small fizz_count = ["fizz","cat","fizz"] def fizz_count(x): count=0 for item in x: if item=="fizz": count=count+1 return count output: 2 String Looping: for letter in "Codecademy": print letter # Empty lines to make the output pretty print (but actually this print can be skipped) print (but actually this print can be skipped) word = "Programming is fun!" for letter in word: # Only print out the letter i if letter == "i": print letter Output: C o d e c a d e m y i i None Supermarket Project: prices={ "banana":4, "apple":2, "orange":1.5, "pear":3 } stock={ "banana":6, "apple":0, "orange":32, "pear":15 } for fruit in prices: print fruit print "price: %s" % price[fruit] print "stock: %s" % stock[fruit] Output: orange price: 1.5 stock: 32 pear price: 3 stock: 15 banana price: 4 stock: 6 apple price: 2 stock: 0 None for fruit in prices: dollar_value=prices[fruit]*stock[fruit] total=total+dollar_value print total Output: 117.0 Making a purchasing: def sum(numbers): total = 0 for number in numbers: total += number return total n = [1, 2, 5, 10, 13] print sum(n) def compute_bill(food): total=0 for fruit in food: total+=prices[fruit] return total (To sum up all the prices for each fruit together) def compute_bill(food): total=0 for fruit in food: if stock[fruit]>0: total+=prices[fruit] stock[fruit]-=1 return total (To sum up the fruit which in stocks & reduce the inventory after purchasing by 1) Chapter 6: School Database Case Study Task: Create three dictionaries: lloyd, alice, and tyler. Give each dictionary the keys "name", "homework", "quizzes", and "tests". Solution: lloyd={"name":"Lloyd", "homework":[], "quizzes":[], "tests":[] } alice={"name":"Alice", "homework":[], "quizzes":[], "tests":[] } tyler={"name":"Tyler", "homework":[], "quizzes":[], "tests":[] } Task: To add value into the database Solution: lloyd["homework"]=90, 97, 75, 92 lloyd["quizzes"]=88, 40, 94 lloyd["tests"]=75, 90 Task: Below your code, create a list called students that contains lloyd, alice, and tyler. Solution: students=[lloyd,alice,tyler] Task: for each student in your students list, print out that student's data, as follows: Solution: for student in students: print student["name"] print student["homework"] print student["quizzes"] print student["tests"] Output: Lloyd (90, 97, 75, 92) (88, 40, 94) (75, 90) Alice [100.0, 92.0, 98.0, 100.0] [82.0, 83.0, 91.0] [89.0, 97.0] Tyler [0.0, 87.0, 75.0, 22.0] [0.0, 75.0, 78.0] [100.0, 100.0] None What is float()? 5 / 2 # 2 5.0 / 2 # 2.5 float(5) / 2 # 2.5 To stay the float(5) can be divided into a decimal place digit Task: Write a function average that takes a list of numbers and returns the average. Solution: def average(numbers): total=sum(numbers) total=float(total) result=total/len(numbers) return result Task: Write a function called get_averagethat takes a student dictionary (like lloyd, alice, or tyler) as input and returns his/her weighted average. Define a function called get_average that takes one argument called student. Make a variable homework that stores the average() of student["homework"]. Repeat step 2 for "quizzes" and "tests". Multiply the 3 averages by their weights and return the sum of those three. Homework is 10%, quizzes are 30% and tests are 60%. Solution: def get_average(student): homework=average(student["homework"]) quizzes=average(student["quizzes"]) tests=average(student["tests"]) return 0.1*homework+0.3*quizzes+0.6*tests Task: Define a new function called get_letter_grade that has one argument called score. Expect score to be a number. Inside your function, test scoreusing a chain of if: / elif: /else: statements, like so: If score is 90 or above: return "A" Else if score is 80 or above: return"B" Else if score is 70 or above: return"C" Else if score is 60 or above: return"D" Otherwise: return "F" Finally, test your function! Call your get_letter_grade function with the result of get_average(lloyd). Print the resulting letter grade. Solution: def get_letter_grade(score): if score>= 90: return "A" elif score>= 80: return "B" elif score>= 70: return "C" elif score>= 60: return "D" else: return "F" Task: Define a function called get_class_average that has one argument students. You can expect students to be a list containing your three students. First, make an empty list called results. For each student item in the class list, calculate get_average(student) and then call results.append() with that result. Finally, return the result of calling average() with results. Solution: def get_class_average(students=[lloyd,alice,tyler]): results=[] for student in students: ga=get_average(student) results.append(ga) return average(results) return average(results) Task: Finally, print out the result of calling get_class_average with your students list. Your studentsshould be [lloyd, alice, tyler]. Then, print the result of get_letter_grade for the class's average. Solution: print get_class_average(students=[lloyd,alice,tyler]) print get_letter_grade(get_class_average(students=[lloyd,alice,tyler]))