Lesson 3 · Full-Length Courses

Learn Python: A Full Course for Beginners

This lesson covers Python from the ground up: variables, strings, numbers, lists, tuples, dictionaries, functions, conditionals, loops, files, modules, and…

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CourseFull-Length Courses
Lesson3 of 7
Video1 h 4 min
FormatJupyter notebook · 43 code cells

What you'll learn

Installing Python
Setting Up VS Code and Your First Notebook
Mini Project: Mad Libs
Lists
Dictionaries
Mini Project: Guessing Game
Comments
Modules

Data

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Learn Python: A Full Course for Beginners#

This lesson covers Python from the ground up: variables, strings, numbers, lists, tuples, dictionaries, functions, conditionals, loops, files, modules, and classes.
Every example runs inside a Jupyter Notebook cell in VS Code, so you can run, tweak, and re-run each idea as you go.
No prior programming experience is required.

Installing Python#

Go to python.org, open Downloads, and download the latest version of Python 3 for your operating system.
On Windows, before clicking Install, check the box that says 'Add python.exe to PATH', which lets your terminal and VS Code find Python.
On macOS, run the installer package and follow the prompts.

Setting Up VS Code and Your First Notebook#

Install Visual Studio Code from code.visualstudio.com.
Open the Extensions view and install the Python extension and the Jupyter extension, both published by Microsoft.
Open the Command Palette with Control plus Shift plus P (Command plus Shift plus P on Mac), type 'Create: New Jupyter Notebook', and press Enter.
In the top right corner of the notebook, click Select Kernel and choose your installed Python interpreter.

print('Hello World')

Hello World

print(' /')
print('/  ')
print('|  ')
print('|__')

 /
/  
|  
|__

character_name = 'John'
character_age = 35
print('There once was a man named ' + character_name + '. He was ' + str(character_age) + ' years old.')

There once was a man named John. He was 35 years old.

character_name = 'Tom'
character_age = 50
print('There once was a man named ' + character_name + '. He was ' + str(character_age) + ' years old.')

There once was a man named Tom. He was 50 years old.

character_name = 'John'
character_age = 35.5
is_male = True
print(character_name, character_age, is_male)

John 35.5 True

phrase = 'Learn Python'
print(phrase + '\n' + 'is fun')
print('He said, \'hello\'')
print('A backslash: \\')

Learn Python
is fun
He said, 'hello'
A backslash: \

phrase = 'Learn Python'
print(phrase + ' is cool')
print(phrase.lower())
print(phrase.upper())
print(phrase.upper().isupper())
print(len(phrase))
print(phrase[0])
print(phrase.index('P'))
print(phrase.replace('Learn', 'Master'))

Learn Python is cool
learn python
LEARN PYTHON
True
12
L
6
Master Python

print(3 + 4.5)
print(3 * 4 + 5)
print(3 * (4 + 5))
print(10 % 3)

import math
my_num = -5
print(abs(my_num))
print(pow(3, 2))
print(max(4, 6))
print(min(4, 6))
print(round(3.7))
print(math.floor(3.7))
print(math.ceil(3.2))
print(math.sqrt(36))

name = input('Enter your name: ')
age = input('Enter your age: ')
print(f'Hello {name}, you are {age}')

Hello John, you are 25

num1 = input('Enter first number: ')
num2 = input('Enter second number: ')
result = num1 + num2
print(result)

58.3

num1 = float(input('Enter first number: '))
num2 = float(input('Enter second number: '))
result = num1 + num2
print(result)

9.5

Mini Project: Mad Libs#

A mad lib is a short story with a few words replaced by blanks, like a color, a plural noun, or a celebrity name, that the player fills in themselves.
We will ask the user for a color, a plural noun, and a celebrity, then splice their answers into a short poem.

color = input('Enter a color: ')
plural_noun = input('Enter a plural noun: ')
celebrity = input('Enter a celebrity: ')
print('Roses are ' + color)
print(plural_noun + ' are blue')
print('I love ' + celebrity)

Roses are magenta
microwaves are blue
I love Tom Hanks

Lists#

A list lets us store many related values together in one structure, rather than one value per variable.
Lists can hold strings, numbers, Booleans, or a mix of all three.

friends = ['Kevin', 'Karen', 'Jim']
print(friends)
print(friends[0])
print(friends[2])
print(friends[-1])
friends[1] = 'Mike'
print(friends)

['Kevin', 'Karen', 'Jim']
Kevin
Jim
Jim
['Kevin', 'Mike', 'Jim']

friends = ['Kevin', 'Karen', 'Jim', 'Oscar', 'Toby']
lucky_numbers = [4, 8, 15, 16, 23]
friends.extend(lucky_numbers)
print(friends)
friends.append('Creed')
print(friends)
friends.insert(1, 'Kelly')
print(friends)
friends.remove('Jim')
print(friends)
friends.pop()
print(friends)
print(friends.index('Oscar'))
print(friends.count('Kevin'))
names = ['Toby', 'Kevin', 'Oscar', 'Creed']
names.sort()
print(names)
names.reverse()
print(names)
names_copy = names.copy()
print(names_copy)

['Kevin', 'Karen', 'Jim', 'Oscar', 'Toby', 4, 8, 15, 16, 23]
['Kevin', 'Karen', 'Jim', 'Oscar', 'Toby', 4, 8, 15, 16, 23, 'Creed']
['Kevin', 'Kelly', 'Karen', 'Jim', 'Oscar', 'Toby', 4, 8, 15, 16, 23, 'Creed']
['Kevin', 'Kelly', 'Karen', 'Oscar', 'Toby', 4, 8, 15, 16, 23, 'Creed']
['Kevin', 'Kelly', 'Karen', 'Oscar', 'Toby', 4, 8, 15, 16, 23]
3
1
['Creed', 'Kevin', 'Oscar', 'Toby']
['Toby', 'Oscar', 'Kevin', 'Creed']
['Toby', 'Oscar', 'Kevin', 'Creed']

coordinates = (4, 5)
print(coordinates[0])
print(coordinates[1])
coordinates[0] = 10

4
5

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[16], line 4
      2 print(coordinates[0])
      3 print(coordinates[1])
----> 4 coordinates[0] = 10

TypeError: 'tuple' object does not support item assignment

def say_hi():
    print('Hello User')


say_hi()

Hello User

def say_hi(name, age):
    print(f'Hello {name}, you are {age}')


say_hi('Mike', 35)
say_hi('Steve', 70)

Hello Mike, you are 35
Hello Steve, you are 70

def cube(num):
    return num * num * num


result = cube(3)
print(result)

is_male = True
is_tall = True
if is_male and is_tall:
    print('You are a tall male')
elif is_male and not is_tall:
    print('You are a short male')
elif not is_male and is_tall:
    print('You are not a male but are tall')
else:
    print('You are not a male and not tall')

You are a tall male

def max_num(num1, num2, num3):
    if num1 >= num2 and num1 >= num3:
        return num1
    elif num2 >= num1 and num2 >= num3:
        return num2
    else:
        return num3


print(max_num(3, 4, 5))
print(max_num(140, 4, 5))
print(max_num(3, 4, 300))

5
140
300

num1 = float(input('Enter first number: '))
op = input('Enter operator (+, -, *, /): ')
num2 = float(input('Enter second number: '))
if op == '+':
    print(num1 + num2)
elif op == '-':
    print(num1 - num2)
elif op == '/':
    print(num1 / num2)
elif op == '*':
    print(num1 * num2)
else:
    print('Invalid operator')

28.0

Dictionaries#

A dictionary stores information as key-value pairs: each unique key maps to an associated value.
Dictionaries are created with curly braces, and keys must always be unique.

month_conversions = {
    'Jan': 'January',
    'Feb': 'February',
    'Mar': 'March',
    'Apr': 'April',
}
print(month_conversions['Mar'])
print(month_conversions.get('Dec'))
print(month_conversions.get('Dec', 'Not a valid key'))

March
None
Not a valid key

i = 1
while i <= 5:
    print(i)
    i += 1
print('Done with loop')

1
2
3
4
5
Done with loop

Mini Project: Guessing Game#

We will pick a secret word, then let the user keep guessing until they either guess correctly or run out of tries.
This combines while loops, if statements, and variables that track state across iterations.

secret_word = 'giraffe'
guess = ''
guess_count = 0
guess_limit = 3
out_of_guesses = False

while guess != secret_word and not out_of_guesses:
    if guess_count < guess_limit:
        guess = input('Enter guess: ')
        guess_count += 1
    else:
        out_of_guesses = True

if out_of_guesses:
    print('Out of guesses, you lose')
else:
    print('You win')

You win

for letter in 'Learn Python':
    print(letter)
for friend in ['Jim', 'Karen', 'Kevin']:
    print(friend)

L
e
a
r
n
 
P
y
t
h
o
n
Jim
Karen
Kevin

for index in range(10):
    print(index)
for index in range(3, 10):
    print(index)
friends = ['Jim', 'Karen', 'Kevin']
for index in range(len(friends)):
    print(friends[index])

0
1
2
3
4
5
6
7
8
9
3
4
5
6
7
8
9
Jim
Karen
Kevin

if True:
    print('First iteration')
for index in range(5):
    if index == 0:
        print('First iteration')
    else:
        print('Not first')

First iteration
First iteration
Not first
Not first
Not first
Not first

def raise_to_power(base_num, pow_num):
    result = 1
    for index in range(pow_num):
        result = result * base_num
    return result


print(raise_to_power(3, 2))
print(raise_to_power(2, 3))

9
8

number_grid = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9],
    [0],
]
print(number_grid[0][0])
print(number_grid[2][1])
for row in number_grid:
    for column in row:
        print(column)

def translate(phrase):
    translation = ''
    for letter in phrase:
        if letter.lower() in 'aeiou':
            if letter.isupper():
                translation = translation + 'G'
            else:
                translation = translation + 'g'
        else:
            translation = translation + letter
    return translation


print(translate(input('Enter a phrase: ')))

dgg

Comments#

A comment is a line of text in your code that Python completely ignores when running the program.
Comments start with a hash sign, #, and are meant purely for humans reading the code.
Use comments to explain a tricky line of code, leave yourself a note, or temporarily disable, or 'comment out', a line without deleting it.

number = int(input('Enter a number: '))
print(number)

try:
    number = int(input('Enter a number: '))
    print(number)
except:
    print('Invalid input')

Invalid input

try:
    number = int(input('Enter a number: '))
    result = 10 / number
    print(result)
except ZeroDivisionError:
    print('Divided by zero')
except ValueError:
    print('Invalid input')

2.0

with open('employees.txt', 'w') as employee_file:
    employee_file.write('Jim Salesman\n')
    employee_file.write('Dwight Salesman\n')
    employee_file.write('Pam Receptionist\n')
print('File created')

File created

employee_file = open('employees.txt', 'r')
print(employee_file.readable())
print(employee_file.read())
employee_file.close()

True
Jim Salesman
Dwight Salesman
Pam Receptionist

employee_file = open('employees.txt', 'r')
print(employee_file.readline())
print(employee_file.readline())
employee_file.close()

employee_file = open('employees.txt', 'r')
for employee in employee_file.readlines():
    print(employee)
employee_file.close()

Jim Salesman

Dwight Salesman

Jim Salesman

Dwight Salesman

Pam Receptionist

with open('employees.txt', 'a') as employee_file:
    employee_file.write('Kelly Customer Service\n')

with open('employees.txt', 'r') as employee_file:
    print(employee_file.read())

Jim Salesman
Dwight Salesman
Pam Receptionist
Kelly Customer Service

Modules#

A module is simply a Python file whose functions and variables we can import and reuse in another file, or in this notebook.
Python ships with many built-in modules, like math, which we already imported earlier in this lesson.
Third-party modules, written by other developers, can be installed with pip, Python's package manager, by running 'pip install package-name' in a terminal.

Classes and Objects#

A class lets us define our own custom data type, modeling a real-world thing like a student, a phone, or a chef.
An object is a specific instance of a class, created from that class's template, with its own actual values.

class Student:
    def __init__(self, name, major, gpa, is_on_probation):
        self.name = name
        self.major = major
        self.gpa = gpa
        self.is_on_probation = is_on_probation

student1 = Student('Jim', 'Business', 3.1, False)
student2 = Student('Pam', 'Art', 2.5, True)
print(student1.name)
print(student1.gpa)
print(student2.gpa)

Jim
3.1
2.5

class Student:
    def __init__(self, name, major, gpa):
        self.name = name
        self.major = major
        self.gpa = gpa

    def on_honor_roll(self):
        if self.gpa >= 3.5:
            return True
        else:
            return False


student1 = Student('Oscar', 'Accounting', 3.1)
student2 = Student('Phyllis', 'Business', 3.8)
print(student1.on_honor_roll())
print(student2.on_honor_roll())

False
True

class Question:
    def __init__(self, prompt, answer):
        self.prompt = prompt
        self.answer = answer


question_prompts = [
    'What color are apples?\n(a) Red\n(b) Purple\n(c) Orange\n\n',
    'What color are bananas?\n(a) Teal\n(b) Magenta\n(c) Yellow\n\n',
]
questions = [
    Question(question_prompts[0], 'a'),
    Question(question_prompts[1], 'c'),
]


def run_test(questions):
    score = 0
    for question in questions:
        answer = input(question.prompt)
        if answer == question.answer:
            score += 1
    print(f'You got {score} out of {len(questions)} correct')


run_test(questions)

You got 2 out of 2 correct

class Chef:
    def make_chicken(self):
        print('The chef makes chicken')

    def make_salad(self):
        print('The chef makes a salad')

    def make_special_dish(self):
        print('The chef makes bbq ribs')


class ChineseChef(Chef):
    def make_fried_rice(self):
        print('The chef makes fried rice')

    def make_special_dish(self):
        print('The chef makes orange chicken')


my_chef = Chef()
my_chef.make_special_dish()
my_chinese_chef = ChineseChef()
my_chinese_chef.make_chicken()
my_chinese_chef.make_fried_rice()
my_chinese_chef.make_special_dish()

The chef makes bbq ribs
The chef makes chicken
The chef makes fried rice
The chef makes orange chicken

Recap#

We installed Python and set up a Jupyter Notebook in VS Code as our environment for writing and running code.
We covered variables, strings, numbers, lists, tuples, and dictionaries, along with the built-in functions and methods that work with each.
We covered functions with parameters and return values, if/elif/else, comparison and logical operators, while loops, and for loops with range.
We covered comments, try/except error handling, reading and writing files, modules, and classes with inheritance.
Practicing each example yourself in a Jupyter Notebook in VS Code is the best way to make these concepts stick.

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