limit = 40 number = 3 number * number

# Problem: how do we find the largest square number less than a limit? limit = 40 # Strategy: we try the square of every integer and stop when the square is greater than the limit number = 1 # TODO: while loop here while (number + 1) **2 < limit: number += 1 # get the result result = number * number print("The largest square number less than {} is {}.".format(limit, result))

list(range(2, 6))

# Example: check for prime number # Prime numbers have only two multiplication factors: one and the number itself. # For example, 7 is a prime number because its multiplication factors are 7 and 1. # 6 is not a prime number because its multiplication factors are 1, 2, 3, and 6. # Given a number, we want to check if it is prime. number = 6 for i in range(2, number): if number % i == 0: # if the number is divisible by i, it is not a prime number print("{} is not a prime number because it is divisible by {}".format(number, i)) break if i == number - 1: print("{} is a prime number".format(number))

# now instead of checking a single number, I want you to check a list of numbers # check if the numbers below are prime or not number_list = [26, 39, 51, 53, 57, 79, 85] for number in number_list: # another outer loop for i in range(2, number): # the original loop is now an inner loop if number % i == 0: # if the number is divisible by i, it is not a prime number print("{} is not a prime number because it is divisible by {}".format(number, i)) break if i == number - 1: # if the number is not divisible by any number less than itself, it is a prime print("{} is a prime number".format(number))

# use case for zip letters = ['a', 'b', 'c'] numbers = [1, 2, 3] # how do we iterate through two iterables at once? # answer: zip print(list(zip(letters, numbers)))

for element in zip(letters, numbers): print(element[0], element[1])

for letter, number in zip(letters, numbers): print(letter, number)

# create a zipped element zipped = list(zip(letters, numbers)) print(zipped) zipped[1]

letters = [1, 2, 3] numbers = ['a', 'b', 'c'] booleans = [True, False, True] print(list(zip(letters, numbers, booleans))) letter, number, boolean = list(zip(letters, numbers, booleans))[1] # tuple unpacking boolean

# create a zipped element zipped = list(zip(letters, numbers)) print(zipped) numbers, letters = list(zip(zipped[0], zipped[1], zipped[2]))

letters

# create a zipped element zipped = list(zip(letters, numbers)) print(zipped) # list is a zip # we now pass the list, with each element as an argument letters_unzipped, numbers_unzipped = zip(*zipped) print(letters_unzipped, numbers_unzipped)

set1 = {1,2} set2 = {'a', 'b'} list(zip(set1, set2))

# lets say we have a list letters = ['a', 'b', 'c', 'd'] # METHOD 1: to get the index and value of the element at each iteration # by using a dummy variable index = 0 ## DEMO: for loop here for letter in letters: print(index, letter) index += 1

# lets say we have a list letters = ['a', 'b', 'c', 'd'] # METHOD 2: to get the index and value of the element at each iteration # by using zip and range for i, letter in zip(range(len(letters)), letters): print(i, letter)

# now lets say we have a list letters = ['a', 'b', 'c', 'd'] # METHOD 3: to get the index and value of the element at each iteration # by using enumerate for (i, letter) in enumerate(letters): print(i, letter)

# Example 1: use zip to label coordinates (physics) # Given the x, y, and z coordinates of points and the corresponding labels, # use zip to print and label the coordinates as so: # label: x, y, z x_coord = [23, 53, 2, -12, 95, 103, 14, -5] y_coord = [677, 233, 405, 433, 905, 376, 432, 445] z_coord = [4, 16, -6, -42, 3, -6, 23, -1] labels = ["F", "J", "A", "Q", "Y", "B", "W", "X"] # for example, the first coordinate should be printed as # F: 23, 677, 4 points = [] for x, y, z, label in zip(x_coord, y_coord, z_coord, labels): points.append("{}: {}, {}, {}".format(label, x, y, z)) for point in points: print(point)

list(enumerate(zip(x_coord, y_coord)))

# Example 2.1: use zip to create a dictionary # Given the names of movie stars and their heights, create a dictionary called cast # the keys of cast are the names of the movie stars # the values of cast are the heights names = ["Andy", "Bobby", "Cindy", "Deborah"] heights = [184, 177, 168, 172] cast = dict(zip(names, heights)) print(cast)

cast.items()

# Example 2.2: unzip the cast into names and heights names_unzipped, heights_unzipped = zip(*cast.items()) print(names_unzipped) print(heights_unzipped)

# Example 2.3: transform a tuple from a 4x3 matrix to a 3x4 matrix data = ((0, 1, 2), (3, 4, 5), (6, 7, 8), (9, 10, 11)) data_transpose = tuple(zip(*data)) print(data_transpose)

%run -i students.py

for name, height in zip(names, heights): print(name + ': ' + str(height))

# Exercise 2.5: create a cast list so that each element contains the name and height of the movie star # For example, the first element of cast should change from "Andy" to "Andy: 184" names = ["Andy", "Bobby", "Cindy", "Deborah"] heights = [184, 177, 168, 172] cast = [] # Solution 2: append to a new list by iterating with zip for names, height in zip(names, heights): cast.append(name + ": " + str(height)) print(cast)

num = num_list[0] odd5 = [] # check if it's odd if num % 2 != 0: odd5.append(num) print(odd5)

# Exercise 2: HTML List Generator items = ['Hello World', 'World Hello'] html_str = "<ul>\n<li>Hello World</li>\n<li>I am the best</li>\n</ul>" print(html_str)

item = items[0] html_str = "<ul>\n" html_str += "<li>" + item + "</li>\n" print(html_str)

number = 4 number * (number - 1) * (number - 2) * (number - 3)

# SOLUTION 1: WHILE LOOP # number to find the factorial of number = 4 # 24 number = 5 #120 number = 6 #720 # start with our product equal to one product = 1 # track the current number being multiplied current = 1 # TODO: write your while loop here # print the factorial of number print("The factorial of {} is: {}".format(number, product))