🐍 30 Days Of Python

# Day	Topics
01	Introduction

• 🐍 30 Days Of Python
• 📘 Day 1
  • Welcome
  • Introduction
  • Why Python ?
  • Environment Setup
    • Installing Python
    • Python Shell
    • Installing Visual Studio Code
      • How to use visual studio code
  • Basic Python
    • Python Syntax
    • Python Indentation
    • Comments
    • Data types
      • Number
      • String
      • Booleans
      • List
      • Dictionary
      • Tuple
      • Set

📘 Day 1

Welcome

Congratulations for deciding to participate in a 30 days of Python programming challenge . In this challenge you will learn everything you need to be a python programmer and the whole concept of programming. In the end of the challenge you will get a 30DaysOfPython programming challenge certificate.

Introduction

Python is a high-level programming language for general-purpose programming. It is an open source, interpreted, objected-oriented programming language. Python was created by a Dutch programmer, Guido van Rossum. The name of Python programming language was derived from a British sketch comedy series, Monty Python's Flying Circus. The first version was released on February 20, 1991. This 30 days of Python challenge will help you learn the latest version of Python, Python 3 step by step. The topics are broken down into 30 days, where each day contains several topics with easy-to-understand explanations, real-world examples, many hands on exercises and projects.

This challenge is designed for beginners and professionals who want to learn python programming language. It may take 30 to 100 days to complete the challenge, people who actively participate on the telegram group have a high probability of completing the challenge.

This challenge is easy to read, written in conversational English, engaging, motivating and at the same time, it is very demanding. You need to allocate much time to finish this challenge.

Why Python ?

It is a programming language which is very close to human language and because of that it is easy to learn and use. Python is used by various industries and companies (including Google). It has been used to develop web applications, desktop applications, system adminstration, and machine learning libraries. Python is highly embraced language in the data science and machine learning community. I hope this is enough to convince you to start learning Python. Python is eating the world and you are killing it before it eats you.

Environment Setup

Installing Python

To run a python script you need to install python. Let's download python. If your are a windows user. Click the button encircled in red.

If you are a macOS user. Click the button encircled in red.

To check if python is installed write the following command on your device terminal.

python --version

As you can see from the terminal, I am using Python 3.7.5 version at the moment. Your version of Python might be different from mine by but it should be 3.6 or above. If you mange to see the python version, well done. Python has been installed on your machine. Continue to the next section.

Python Shell

Python is an interpreted scripting language, so it does not need to be compiled. It means it executes the code line by line. Python comes with a Python Shell (Python Interactive Shell). It is used to execute a single python command and get the result.

Python Shell waits for the Python code from the user. When you enter the code, it interprets the code and shows the result in the next line. Open your terminal or command prompt(cmd) and write:

python

The Python interactive shell is opened and it is waiting for you to write Python code(Python script). You will write your Python script next to this symbol >>> and then click Enter. Let us write our very first script on the Python scripting shell.

Well done, you wrote your first Python script on Python interactive shell. How do we close the Python interactive shell ? To close the shell, next to this symbol >> write exit() command and press Enter.

Now, you know how to open the Python interactive shell and how to exit from it.

Python will give you results if you write scripts that Python understands, if not it returns errors. Let's make a deliberate mistake and see what Python will return.

As you can see from the returned error, Python is so clever that it knows the mistake we made and which was Syntax Error: invalid syntax. Using x as multiplication in Python is a syntax error because (x) is not a valid syntax in Python. Instead of (x) we use asterisk (*) for multiplication. The returned error clearly shows what to fix.

The process of identifying and removing errors from a program is called debugging. Let us debug it by putting * in place of x.

Our bug was fixed, the code ran and we got a result we were expecting. As a programmer you will see such kind of errors on daily basis. It is good to know how to debug. To be good at debugging you should understand what kind of errors you are facing. Some of the Python errors you may encounter are SyntaxError, IndexError, NameError, ModuleNotFoundError, KeyError, ImportError, AttributeError, TypeError, ValueError, ZeroDivisionError etc. We will see more about different Python error types in later sections.

Let us practice more how to use Python interactive shell. Go to your terminal or command prompt and write the word python.

The Python interactive shell is opened. Let us do some basic mathematical operations (addition, subtraction, multiplication, division, modulus, exponential).

Let us do some maths first before we write any Python code:

• 2 + 3 is 5
• 3 - 2 is 1
• 3 * 2 is 6
• 3 / 2 is 1.5
• 3 ** 2 is the same as 3 * 3

In python we have the following additional operations:

• 3 % 2 = 1 => which means finding the remainder
• 3 // 2 = 1 => which means removing the remainder

Let us change the above mathematical expressions to Python code. The Python shell has been opened and let us write a comment at the very beginning of the shell.

A comment is a part of the code which is not executed by python. So we can leave some text in our code to make our code more readable. Python does not run the comment part. A comment in python starts with hash(#) symbol. This is how you write a comment in python

 # comment starts with hash
 # this is a python comment, because it starts with a (#) symbol

Before we move on to the next section, let us practice more on the Python interactive shell. Close the opened shell by writing exit() on the shell and open it again and let us practice how to write text on the Python shell.

Installing Visual Studio Code

The Python interactive shell is good to try and test small script codes but it will not be for a big project. In real work environment, developers use different code editors to write codes. In this 30 days of Python programming challenge we will use visual studio code. Visual studio code is a very popular open source text editor. I am a fan of vscode and I would recommend to download visual studio code, but if you are in favor of other editors, feel free to follow with what you have.

If you installed visual studio code, let us see how to use it. If you prefer a video, you can follow this Visual Studio Code for Python Video tutorial

How to use visual studio code

Open the visual studio code by double clicking the visual studio icon. When you open it you will get this kind of interface. Try to interact with the labeled icons.

Create a folder named 30DaysOfPython on your desktop. Then open it using visual studio code.

After opening it you will see shortcuts for creating files and folders inside of 30DaysOfPython project's directory. As you can see below, I have created the very first file, helloworld.py. You can do the same.

After a long day of coding, you want to close your code editor, right? This is how you will close the opened project.

Congratulations, you have finished setting up the development environment. Let us start coding.

Basic Python

Python Syntax

A Python script can be written in Python interactive shell or in the code editor. A Python file has an extension .py.

Python Indentation

An indentation is a white space in a text. Indentation in many languages is used to increase code readability, however Python uses indentation to create block of codes. In other programming languages curly brackets are used to create blocks of codes instead of indentation. One of the common bugs when writing python code is wrong indentation.

Comments

Comments are very important to make the code more readable and to leave remarks in our code. Python does not run comment parts of our code. Any text starting with hash(#) in Python is a comment.

Example: Single Line Comment

    # This is the first comment
    # This is the second comment
    # Python is eating the world

Example: Multiline Comment

Triple quote can be used for multiline comment if it is not assigned to a variable

"""This is multiline comment
multiline comment takes multiple lines.
python is eating the world
"""

Data types

In Python there are several types of data types. Let us get started with the most common ones. Different data types will be covered in detail in other sections. For the time being, let us just go through the different data types and get familiar with them. You do not have to have a clear understanding now.

Number

• Integer: Integer(negative, zero and positive) numbers Example: ... -3, -2, -1, 0, 1, 2, 3 ...
• Float: Decimal number Example ... -3.5, -2.25, -1.0, 0.0, 1.1, 2.2, 3.5 ...
• Complex Example 1 + j, 2 + 4j

String

A collection of one or more characters under a single or double quote. If a string is more than one sentence then we use a triple quote.

Example:

'Asabeneh'
'Finland'
'Python'
'I love teaching'
'I hope you are enjoying the first day of 30DaysOfPython Challenge'

Booleans

A boolean data type is either a True or False value. T and F should be always uppercase.

Example:

    True  #  Is the light on? If it is on, then the value is True
    False # Is the light on? If it is off, then the value is False

List

Python list is an ordered collection which allows to store different data type items. A list is similar to an array in JavaScript.

Example:

[0, 1, 2, 3, 4, 5]  # all are the same data types - a list of numbers
['Banana', 'Orange', 'Mango', 'Avocado'] # all the same data types - a list of strings (fruits)
['Finland','Estonia', 'Sweden','Norway'] # all the same data types - a list of strings (countries)
['Banana', 10, False, 9.81] # different data types in the list - string, integer, boolean and float

Dictionary

A Python dictionary object is an unordered collection of data in a key value pair format.

Example:

{
'first_name':'Asabeneh',
'last_name':'Yetayeh',
'country':'Finland', 
'age':250, 
'is_married':True,
'skills':['JS', 'React', 'Node', 'Python']
}

Tuple

A tuple is an ordered collection of different data types like list but tuples can not be modified once they are created. They are immutable.

Example:

('Asabeneh', 'Pawel', 'Brook', 'Abraham', 'Lidiya') # Names

('Earth', 'Jupiter', 'Neptune', 'Mars', 'Venus', 'Saturn', 'Uranus', 'Mercury') # planets

Set

A set is a collection of data types similar to list and tuple. Unlike list and tuple, set is not an ordered collection of items. Like in Mathematics, set in Python stores only unique items.

In later sections, we will go in detail about each and every Python data type.

Example:

{2, 4, 3, 5}
{3.14, 9.81, 2.7} # order is not important in set

Checking Data types

To check the data type of certain data/variable we use the type function. In the following terminal you will see different python data types:

Python File

First open your project folder, 30DaysOfPython. If you don't have this folder, create a folder name called 30DaysOfPython. Inside this folder, create a file called helloworld.py. Now, let's do what we did on python interactive shell using visual studio code.

The Python interactive shell was printing without using print but on visual studio code to see our result we should use a built in function _print(). The print() built-in function takes one or more arguments as follows print('arument1', 'argument2', 'argument3'). See the examples below.

Example:

The file name is helloworld.py

# Day 1 - 30DaysOfPython Challenge

print(2 + 3)             # addition(+)
print(3 - 1)             # subtraction(-)
print(2 * 3)             # multiplication(*)
print(3 / 2)             # division(/)
print(3 ** 2)            # exponential(**)
print(3 % 2)             # modulus(%)
print(3 // 2)            # Floor division operator(//)

# Checking data types
print(type(10))          # Int
print(type(3.14))        # Float
print(type(1 + 3j))      # Complex number
print(type('Asabeneh'))  # String
print(type([1, 2, 3]))   # List
print(type({'name':'Asabeneh'})) # Dictionary
print(type({9.8, 3.14, 2.7}))    # Set
print(type((9.8, 3.14, 2.7)))    # Tuple

To run the python file check the image below. You can run the python file either by running the green button on Visual Studio Code or by typing python helloworld.py in the terminal .

🌕 You are amazing. You have just completed day 1 challenge and you are on your way to greatness. Now do some exercises for your brain and muscles.

📘 Day 2

Built in functions

In Python we have lots of built-in functions. Built-in functions are globally available for your use that mean you can make use of the built-in functions without importing or configuring. Some of the most commonly used Python built-in functions are the following: print(), len(), type(), int(), float(), str(), input(), list(), dict(), min(), max(), sum(), sorted(), open(), file(), help(), and dir(). In the following table you will see an exhaustive list of Python built-in functions taken from python documentation.

Let us open the Python shell and start using some of the most common built-in functions.

Let us practice more by using different built-in functions

As you can see from the terminal above, Python has got reserved words. We do not use reserved words to declare variables or functions. We will cover variables in the next section.

I believe, by now you are familiar with built-in functions. Let us do one more practice of built-in functions and we will move on to the next section.

Variables

Variables store data in a computer memory. Mnemonic variables are recommended to use in many programming languages. A mnemonic variable is a variable name that can be easily remembered and associated. A variable refers to a memory address in which data is stored. Number at the beginning, special character, hyphen are not allowed when naming a variable. A variable can have a short name (like x, y, z), but a more descriptive name (firstname, lastname, age, country) is highly recommended.

Python Variable Name Rules

• A variable name must start with a letter or the underscore character
• A variable name cannot start with a number
• A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
• Variable names are case-sensitive (firstname, Firstname, FirstName and FIRSTNAME) are different variables)

Here are some example of valid variable names:

firstname
lastname
age
country
city
first_name
last_name
capital_city
_if # if we want to use reserved word as a variable
year_2021
year2021
current_year_2021
birth_year
num1
num2

Invalid variables names

first-name
first@name
first$name
num-1
1num

We will use standard Python variable naming style which has been adopted by many Python developers. Python developers use snake case(snake_case) variable naming convention. We use underscore character after each word for a variable containing more than one word(eg. first_name, last_name, engine_rotation_speed). The example below is an example of standard naming of variables, underscore is required when the variable name is more than one word.

When we assign a certain data type to a variable, it is called variable declaration. For instance in the example below my first name is assigned to a variable first_name. The equal sign is an assignment operator. Assigning means storing data in the variable. The equal sign in Python is not equality as in Mathematics.

Example:

# Variables in Python
first_name = 'Asabeneh'
last_name = 'Yetayeh'
country = 'Finland'
city = 'Helsinki'
age = 250
is_married = True
skills = ['HTML', 'CSS', 'JS', 'React', 'Python']
person_info = {
   'firstname':'Asabeneh',
   'lastname':'Yetayeh',
   'country':'Finland',
   'city':'Helsinki'
   }

Let us use the print() and len() built-in functions. Print function takes unlimited number of arguments. An argument is a value which we can be passed or put inside the function parenthesis, see the example below.

Example:

print('Hello, World!') # The text Hello, World! is an argument
print('Hello',',', 'World','!') # it can take multiple arguments, four arguments have been passed
print(len('Hello, World!')) # it takes only one argument

Let us print and also find the length of the variables declared at the top:

Example:

# Printing the values stored in the variables

print('First name:', first_name)
print('First name length:', len(first_name))
print('Last name: ', last_name)
print('Last name length: ', len(last_name))
print('Country: ', country)
print('City: ', city)
print('Age: ', age)
print('Married: ', is_married)
print('Skills: ', skills)
print('Person information: ', person_info)

Declaring Multiple Variable in a Line

Multiple variables can also be declared in one line:

Example:

first_name, last_name, country, age, is_married = 'Asabeneh', 'Yetayeh', 'Helsink', 250, True

print(first_name, last_name, country, age, is_married)
print('First name:', first_name)
print('Last name: ', last_name)
print('Country: ', country)
print('Age: ', age)
print('Married: ', is_married)

Getting user input using the input() built-in function. Let us assign the data we get from a user into first_name and age variables. Example:

first_name = input('What is your name: ')
age = input('How old are you? ')

print(first_name)
print(age)

Data Types

There are several data types in Python. To identify the data type we use the type built-in function. I would like to ask you to focus on understanding different data types very well. When it comes to programming, it is all about data types. I introduced data types at the very beginning and it comes again, because every topic is related to data types. We will cover data types in more detail in their respective sections.

Checking Data types and Casting

• Check Data types: To check the data type of certain data/variable we use the type Example:

# Different python data types
# Let's declare variables with various data types

first_name = 'Asabeneh'     # str
last_name = 'Yetayeh'       # str
country = 'Finland'         # str
city= 'Helsinki'            # str
age = 250                   # int, it is not my real age, don't worry about it

# Printing out types
print(type('Asabeneh'))     # str
print(type(first_name))     # str
print(type(10))             # int
print(type(3.14))           # float
print(type(1 + 1j))         # complex
print(type(True))           # bool
print(type([1, 2, 3, 4]))     # list
print(type({'name':'Asabeneh','age':250, 'is_married':250}))    # dict
print(type((1,2)))                                              # tuple
print(type(zip([1,2],[3,4])))                                   # set

• Casting: Converting one data type to another data type. We use int(), float(), str(), list, set When we do arithmetic operations string numbers should be first converted to int or float otherwise it will return an error. If we concatenate a number with a string, the number should be first converted to a string. We will talk about concatenation in String section.

  Example:

# int to float
num_int = 10
print('num_int',num_int)         # 10
num_float = float(num_int)
print('num_float:', num_float)   # 10.0

# float to int
gravity = 9.81
print(int(gravity))             # 9

# int to str
num_int = 10
print(num_int)                  # 10
num_str = str(num_int)
print(num_str)                  # '10'

# str to int or float
num_str = '10.6'
print('num_int', int(num_str))      # 10
print('num_float', float(num_str))  # 10.6

# str to list
first_name = 'Asabeneh'
print(first_name)               # 'Asabeneh'
first_name_to_list = list(first_name)
print(first_name_to_list)            # ['A', 's', 'a', 'b', 'e', 'n', 'e', 'h']

Numbers

Number data types in Python:

1. Integers: Integer(negative, zero and positive) numbers Example: ... -3, -2, -1, 0, 1, 2, 3 ...

2. Floating Point Numbers(Decimal numbers) Example: ... -3.5, -2.25, -1.0, 0.0, 1.1, 2.2, 3.5 ...

3. Complex Numbers Example: 1 + j, 2 + 4j, 1 - 1j

🌕 You are awesome. You have just completed day 2 challenges and you are two steps ahead on your way to greatness. Now do some exercises for your brain and muscles.

💻 Exercises - Day 2

Exercises: Level 1

1. Inside 30DaysOfPython create a folder called day_2. Inside this folder create a file named variables.py
2. Write a python comment saying 'Day 2: 30 Days of python programming'
3. Declare a first name variable and assign a value to it
4. Declare a last name variable and assign a value to it
5. Declare a full name variable and assign a value to it
6. Declare a country variable and assign a value to it
7. Declare a city variable and assign a value to it
8. Declare an age variable and assign a value to it
9. Declare a year variable and assign a value to it
10. Declare a variable is_married and assign a value to it
11. Declare a variable is_true and assign a value to it
12. Declare a variable is_light_on and assign a value to it
13. Declare multiple variable on one line

Exercises: Level 2

1. Check the data type of all your variables using type() built-in function
2. Using the len() built-in function, find the length of your first name
3. Compare the length of your first name and your last name
4. Declare 5 as num_one and 4 as num_two
   1. Add num_one and num_two and assign the value to a variable total
   2. Subtract num_two from num_one and assign the value to a variable diff
   3. Multiply num_two and num_one and assign the value to a variable product
   4. Divide num_one by num_two and assign the value to a variable division
   5. Use modulus division to find num_two divided by num_one and assign the value to a variable remainder
   6. Calculate num_one to the power of num_two and assign the value to a variable exp
   7. Find floor division of num_one by num_two and assign the value to a variable floor_division
5. The radius of a circle is 30 meters.
   1. Calculate the area of a circle and assign the value to a variable name of area_of_circle
   2. Calculate the circumference of a circle and assign the value to a variable name of circum_of_circle
   3. Take radius as user input and calculate the area.
6. Use the built-in input function to get first name, last name, country and age from a user and store the value to their corresponding variable names
7. Run help('keywords') in Python shell or in your file to check for the Python reserved words or keywords

🎉 CONGRATULATIONS ! 🎉