In this part of my Learn to Program series we cover one of the most important topics which is lists.We’ll look at numerous list functions, how to sort lists with the Bubble Sort, List Comprehensions, simple Debugging and much more.

This tutorial series is all about learning how to solve problems, and those problems get more complex with each tutorial. Make sure you watch the first part before moving on. The code follows the video below.

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Code & Transcript

# ---------- LEARN TO PROGRAM 6 ----------

import random
import math

# With lists we can refer to groups of data with 1 name

# Each item in the list corresponds to a number (index)
# just like how people have identification numbers.
# By default the 1st item in a list has the index 0

# [0 : "string"] [1 : 1.234] [2 : 28] [3 : "c"]

# Python lists can grow in size and can contain data
# of any type

randList = ["string", 1.234, 28]

# Create a list with range
oneToTen = list(range(10))

# An awesome thing about lists is that you can use many
# of the same functions with them that you used with strings

# Combine lists
randList = randList + oneToTen

# Get the 1st item with an index
print(randList[0])

# Get the length
print("List Length :", len(randList))

# Slice a list to get 1st 3 items
first3 = randList[0:3]

# Cycle through the list and print the index
for i in first3:
    print("{} : {}".format(first3.index(i), i))

# You can repeat a list item with *
print(first3[0] * 3)

# You can see if a list contains an item
print("string" in first3)

# You can get the index of a matching item
print("Index of string :", first3.index("string"))

# Find out how many times an item is in the list
print("How many strings :", first3.count("string"))

# You can change a list item
first3[0] = "New String"

for i in first3:
    print("{} : {}".format(first3.index(i), i))

# Append a value to the end of a list
first3.append("Another")

# ---------- PROBLEM : CREATE A RANDOM LIST ----------
# Generate a random list of 5 values between 1 and 9
numList = []
for i in range(5):
    numList.append(random.randrange(1, 9))

# ---------- SORT A LIST : BUBBLE SORT ----------
# The Bubble sort is a way to sort a list
# It works this way
# 1. An outer loop decreases in size each time
# 2. The goal is to have the largest number at the end of
#    the list when the outer loop completes 1 cycle
# 3. The inner loop starts comparing indexes at the beginning
#    of the loop
# 4. Check if list[Index] > list[Index + 1]
# 5. If so swap the index values
# 6. When the inner loop completes the largest number is at
#    the end of the list
# 7. Decrement the outer loop by 1

# Create the value that will decrement for the outer loop
# Its value is the last index in the list
i = len(numList) - 1

while i > 1:

    j = 0

    while j < i:

        # Tracks the comparison of index values
        print("\nIs {} > {}".format(numList[j], numList[j+1]))
        print()

        # If the value on the left is bigger switch values
        if numList[j] > numList[j+1]:

            print("Switch")

            temp = numList[j]
            numList[j] = numList[j + 1]
            numList[j + 1] = temp

        else:
            print("Don't Switch")

        j += 1

        # Track changes to the list
        for k in numList:
            print(k, end=", ")
        print()

    print("END OF ROUND")

    i -= 1

for k in numList:
    print(k, end=", ")
print()

# ---------- MORE LIST FUNCTIONS ----------
numList = []
for i in range(5):
    numList.append(random.randrange(1, 9))

# Sort a list
numList.sort()

# Reverse a list
numList.reverse()

for k in numList:
    print(k, end=", ")
print()

# Insert value at index insert(index, value)
numList.insert(5, 10)

# Delete first occurrence of value
numList.remove(10)

for k in numList:
    print(k, end=", ")
print()

# Remove item at index
numList.pop(2)

for k in numList:
    print(k, end=", ")
print()

# ---------- LIST COMPREHENSIONS ----------
# You can construct lists in interesting ways using
# list comprehensions

# Perform an operation on each item in the list

# Create a list of even values
evenList = [i*2 for i in range(10)]

for k in evenList:
    print(k, end=", ")
print()

# List of lists containing values to the power of
# 2, 3, 4
numList = [1,2,3,4,5]

listOfValues = [[math.pow(m, 2), math.pow(m, 3), math.pow(m, 4)]
                for m in numList]

for k in listOfValues:
    print(k)
print()

# Create a 10 x 10 list
multiDList = [[0] * 10 for i in range(10)]

# Change a value in the multidimensional list
multiDList[0][1] = 10

# Get the 2nd item in the 1st list
# It may help to think of it as the 2nd item in the 1st row
print(multiDList[0][1])

# Get the 2nd item in the 2nd list
print(multiDList[1][1])

# ---------- MULTIDIMENSIONAL LIST ----------

# Show how indexes work with a multidimensional list
listTable = [[0] * 10 for i in range(10)]

for i in range(10):

    for j in range(10):
        listTable[i][j] = "{} : {}".format(i, j)

for i in range(10):

    for j in range(10):
        print(listTable[i][j], end=" || ")
    print()

# ---------- PROBLEM : CREATE MULTIPLICATION TABLE ----------
# With 2 for loops fill the cells in a multidimensional
# list with a multiplication table using values 1 - 9
'''
1, 2, 3, 4, 5, 6, 7, 8, 9,
2, 4, 6, 8, 10, 12, 14, 16, 18,
3, 6, 9, 12, 15, 18, 21, 24, 27,
4, 8, 12, 16, 20, 24, 28, 32, 36,
5, 10, 15, 20, 25, 30, 35, 40, 45,
6, 12, 18, 24, 30, 36, 42, 48, 54,
7, 14, 21, 28, 35, 42, 49, 56, 63,
8, 16, 24, 32, 40, 48, 56, 64, 72,
9, 18, 27, 36, 45, 54, 63, 72, 81
'''

# Create the multidimensional list
multTable = [[0] * 10 for i in range(10)]

# This will increment for each row
for i in range(1, 10):

    # This will increment for each item in the row
    for j in range(1, 10):

        # Assign the value to the cell
        multTable[i][j] = i * j

# Output the data in the same way you assigned it
for i in range(1, 10):

    for j in range(1, 10):
        print(multTable[i][j], end=", ")

    print()