An Introduction to Python Programming: A Practical Approach: step-by-step approach to Python programming with machine learning fundamental and theoretical principles.

CHAPTER 1

Basics of Python Programming

Nowadays, Python is one of the most popular programming languages. There are many reasons for this, but simply it is easy to read and write Python code. Python provides vast libraries for which you can efficiently make your program. In this chapter, you will see various features, installation, and the making of a simple program of Python.

Structure

In this chapter, we will cover the following topics:

Basic features and history of Python

Installing Python and running Python program to IDE

Writing and executing first Python program

Brief description about various concepts used in Python

Objective

The objective of this chapter is to introduce the concept of Python, its features, and the Installation procedure in Windows and Linux. After completing this chapter, you should be familiar with Python IDE and editors. Also, you will be able to write simple Python programs.

Understanding Python

Python is one of the high-level languages. There are various advantages of high-level languages:

Program is easier and understandable which is written in a high-level language

Program is shorter in a high-level language

The code written in a high-level language is portable, which means it can run on different computers with some modifications.

Due to these preceding advantages, almost all programs are written in high-level languages. Guido van Rossum designed Python in 1991; after that, Python released various versions as shown in table 1.1:

Table 1.1: Python versions with released year

The compiler completes the task which is involved in the compilation process. Moreover, it converts a source code to object code, and after that, the program will be converted to machine understandable code. But an interpreter reads a high-level program and executes it. Python does not follow the compilation process; it is used only as an interpreter. That's why from a computation point of view, Python is very fast. The figures can easily understand it.

Here figure 1.1 shows the structure of the compiler. A compiler translates source code into an object code, which a hardware executor runs:

Figure 1.1: Structure of Compiler

Here figure 1.2, shows the structure of the interpreter. An interpreter processes the program in less time, and it also takes less time to read lines and perform computations:

Figure 1.2: Structure of Interpreter

Python is an interpreted language because an interpreter executes Python programs, but the compilation process is also done in Python. The compilation part is hidden from the programmer that is why it is known as an interpreted language.

There are various reasons Python has become more popular:

It is easy to use because its coding is written in a simple English language. Users can easily understand and write code into Python, so it takes less time to write a program.

It is a very powerful language because it has many libraries where you can easily make a program. An inbuilt library has lots of inbuilt functions where you can insert as per your need.

It is an object-oriented programming language that is why it follows all the object-oriented concepts.

It is integrated with other programming languages such as C, C++, Java, etc.

It is platform-independent, which means if you created a program in one operating system, you could also run that program in another operating system.

It is free and open-source, which means you can install it on your computer without any cost. It can be copied or modified and resold accordingly. This is a solid reason why Python has become more popular.

Installing Python

It works with various operating systems Windows, Linux, macOS, etc. If you want to work in Python, it needs permission from the Python interpreter. Python is available on the website Python.org. Download the right installer for your operating system and run it on the computer. This figure shows a clear understanding of the installer of Python. You can choose the Python installer according to the operating system:

Figure 1.3: Installation Page of Python

Windows

There are various steps for installing Python in Windows. Python does not come preinstalled in Windows systems. However, installing Python is a straightforward process. All you need to do is to download the Python installer from the website, https://www.python.org/, and then run the program. Here are the steps to install it on Windows:

Downloading the Python installer from https://www.python.org/,

Select a Python version:

Figure 1.4: Python versions

Select Windows 64-bit or 32-bit Windows:

Figure 1.5: Installation Setup of Python

Run the Installer.

Don't forget to click the box that indicates Add Python Version to PATH this will confirm that the interpreter is added to the execution path. The final step is to click Install now, and these are all the required steps:

Figure 1.6: Running the Installer

The figure 1.6 shows various optional features during installation. We can select these features as required:

Figure 1.7: Various Options in Python setup

After selecting various features next window shows advanced options, which are shown in figure 1.7. Here, installation location also needs to be selected:

Figure 1.8: Processing of Python Setup

The figure 1.8 shows the installation setup progress; after completion of this step, Python will be successfully installed in the system:

Figure 1.9: Completion of Python setup

The figure 1.9 shows the completion of the Python setup in the system. Now the system is ready to use Python. Python application can be opened by searching from the taskbar; it is shown in figure 1.10:

Figure 1.10: Open Python application

Ubuntu

There are different versions of the Ubuntu distribution, and the installations are different. Moreover, most factory versions of Ubuntu 18.04 or Ubuntu 20.04 come with Python preinstalled; first of all, check your version with the following commands and enter this command on the terminal:

python -version

Update and refresh repository lists

The next step is to update and refresh the list of the repository with the following command:

sudo apt update

Installation of supporting software

There is a following command:

sudo apt install software-properties-common

Add Deadsnakes PPA ((Personal Package Archive))

There is a following command:

sudo add-apt-repository ppa:deadsnakes/ppa

The system will prompt you to press Enter to continue. Do so, and allow it to finish. Refresh the package lists again:

sudo apt update

Install Python 3

Now you can start the installation of Python 3.9 with the command:

sudo apt install python3.9

Allow the process to complete and verify if the Python version was installed successfully:

python -version

The preceding command shows the current version of Python:

Figure 1.11: Python installation through sudo command on Ubuntu

Linux Mint

Installation of Mint is similar to Ubuntu, and installation instruction for Ubuntu can also be used in Mint. A deadsnakes/ppa working well with Mint.

Python IDLE

Python introduces IDLE, which means Integrated Development and Learning Environment. By default, Python contains the IDLE module for windows, and it is not contained in Linux. A development environment provides an interactive platform that contains various tools that makes a program straightforward. There are two types of modes in IDLE which is interactive mode and script mode:

Figure 1.12: Python on Search Bar

The preceding figure 1.12 shows how Python IDE can search through the search bar:

Figure 1.13: Python Shell

There are various types of IDEs are available for Python. Various kinds of IDEs are commercial and freely available such as PyCharm, Kite, Spyder, DLE, Visual Studio Code, Atom, Jupyter, Pydev, Thonny, and many more. Here, we will learn how to use some open-source editors to execute Python scripts or statements.

Anaconda open-source distribution

It is for Python and R programming languages. This distribution is freely available. It contains various applications such as JupyterLab, Jupyter Notebook, QtConsole, Spyder, Glue, Orange, RStudio, and Visual Studio Code.

This distribution is for large-scale data processing, predictive analytics, and scientific computing. The advantage of Anaconda is the massive amount of packages inside it. It would be very easier to make a program and handle huge data under time and space constraints.

Figure 1.14: Anaconda Navigator

Writing and executing first Python program

There are three ways to write and execute a Python program.

Starting Python through Command Line

Starting Python IDLE

Starting Python through Spyder/Jupyter Notebook in Anaconda Prompt

Starting Python through command line

It can be writing a Python code through a command-line approach. When we can execute Python expressions, statements, or instructions from the command line then this type of mode is called interactive mode or interactive prompt. There are the following steps to start a Python code through the command line.

Click the Start button as shown in figure 1.15:

Figure 1.15: Start button

Type Python 3.9 in the search space bar beside the Start button, as shown in figure 1.16:

Figure 1.16: Python 3.9 (64-bit)

Click to open Python 3.9 (64-bit). After that, a command prompt will be open, as shown in figure 1.17:

Figure 1.17: Python 3.9 (64-bit) Command prompt

We can write any expression or statements over here. This is an interactive mode of Python command prompt. Here, we are writing our names through the command prompt, as shown in figure 1.18:

Figure 1.18: Python code through command prompt

To exit the command line of Python 3.9, you can press Ctrl + z and press Enter key or type exit() then press Enter key.

Starting Python IDLE

Python IDLE is another way to write and execute a Python program. It provides an interactive platform that contains various tools that can be used to write a program.

There are the following steps to start a Python through Python IDLE.

Type IDLE in the search space bar beside the start button, as shown in figure 1.19:

Figure 1.19: IDLE (Python 3.9 64 bit)

Click to open an IDLE (Python 3.9 64 bit). After that, an IDLE Shell will open, as shown in figure 1.20:

Figure 1.20: IDLE Shell

We can write any expression or statement over here. This is an interactive mode of Python IDLE. Here, we are writing our names and some basic expressions through this prompt, as shown in figure 1.21:

Figure 1.21: Python code through IDLE Shell

To exit from an IDLE (Python 3.9 64 bit), type exit() and press Ctrl + q.

Starting Python through Spyder in Anaconda Prompt

In this section, we are writing the first program on one of the IDE names Spyder. You can install Spyder separately or through an anaconda prompt. Here we are using Spyder through an anaconda prompt.

There are the following steps to start Python through Spyder in Anaconda prompt.

First of all, we have to install an anaconda prompt, then we simply type anaconda download on Google, as shown in figure 1.22:

Figure 1.22: Anaconda search on Google

Click Individual Edition-Anaconda link, or you can go through the following URL www.anaconda.com/products/individual. The webpage will open, and you can download and install Anaconda, as shown in figure 1.23:

Figure 1.23: Download Anaconda

After installing Anaconda, you can type Anaconda Navigator in the search bar beside the start button, as shown in figure 1.24:

Figure 1.24: Anaconda Navigator

Click to open Anaconda Navigator. After that, the Anaconda Navigator will be open, as shown in figure 1.25:

Figure 1.25: Anaconda Navigator Snippet

Click on the Spyder icon; after that, the Spyder application will be launched, as shown in figure 1.26:

Figure 1.26: Spyder in Anaconda Navigator

After clicking on Spyder applications, Spyder IDE will open, as shown in figure 1.27:

Figure 1.27: Spyder Home

In the Spyder IDE, the left window is used for writing codes. Here we can write python codes as shown in figure 1.28:

Figure 1.28: Code on Spyder

Starting Python through Jupyter Notebook

The following steps will be used to write a program in Jupyter notebook.

Search Jupyter notebook from start menu as shown in the figure 1.29:

Figure 1.29: Searching Jupyter Notebook

After clicking on Jupyter Notebook, it will open as shown in figure 1.30:

Figure 1.30: Jupyter Notebook

Now, we will start a new notebook. For this, we will click on the new Python 3 notebook. The new option is available at the top-right corner of this window. The following figure 1.31 shows an example of a new notebook:

Figure 1.31: Opening a Notebook in Jupyter

We can write Python codes in the notebook cells and execute them by clicking the Run button. The following figure 1.32, gives an example of writing and executing Python codes:

Figure 1.32: Writing codes in Jupyter

Writing and saving Python programs

The following examples show how we create Python scripts, save and execute them in different Python editors.

Example 1.1:

# Display a Name

print (Dr. Brijesh Bakariya)

#Function displaying a name

Output:

Dr. Brijesh Bakariya

The Python file's file extension is .py, so it must be saved by the .py extension and the code should be executed.

Example 1.2:

# Program for the addition of two numbers

num1 = 10

num2 = 20

# Add two numbers

sum = num1 + num2

# Display the sum

print ('The sum of {0} and {1} is {2}'.format(num1, num2, sum))

Output:

The sum of 10 and 20 is 30

Example 1.3:

# Program for addition of two numbers with user input

# input() for taking input from user

num1 = input('Enter first number: ')

num2 = input('Enter second number: ')

# Add two numbers

sum = float(num1) + float(num2)

# Display the sum

print ('The sum of {0} and {1} is {2}'.format(num1, num2, sum))

Output:

The sum of 12.6 and 66.2 is 78.8

Value and types

A value is a small part of the program. It could be a number or a letter. For example, we have an integer number 10, 20 that means this is a value and letter Brijesh, Bakariya is a letter or a string. It is also called a string of letters, this is enclosed in quotation marks.

The type() function tells the type of a value. Let us take some examples where it could be clearly understood.

Example 1.4:

a=type('Amit Kumar')

print (a)

b=type(17)

print (b)

c= type(10.5)

print (c)

Output:

Numbers

This is one of the data types which contain numeric values. This is an immutable data type, which means you can change the value of a number data type, and the result will change.

Python supports integers, floating-point numbers, and complex numbers. There are the following representations of a number data type in Python.

The integer represents as int

Floating-point numbers represent float

Complex numbers represent complex

Let us take an example.

Example 1.5:

a = 5

print (a)

print (type(a))

b=15.2

print (b)

print (type(b))

c = 3 + 2j

print (c + 3)

print (type(c))

Output:

5

15.2

(6+2j)

Getting input

Somewhere we have to interact with the user, the input() method is used to get input from the user.

When you use input() method, then this method uses a dialog box. It is a way of asking the user to provide some type of input. There are two types of methods for getting input from the user:

input (prompt)

raw_input (prompt)

input(): This function first takes the input from the user and then evaluates the expression.

This method's beauty is that it is automatically identified whether the user entered a string or a number or list. If the input provided is not correct, then either syntax error or exception is raised by Python.

Let's understand how the input() function works?

input() function executes and waits until the user has given input. The text or message displays on the output screen. Whatever you enter as an input, the input() function converts it into a string. If you enter an integer value, still the input() function converts it into a string. You need to explicitly convert it into an integer in your code using typecasting.

Python 3.6 uses the input() method, and here we are taking an example of Python 3.6 or higher version.

Example 1.6:

# input() for taking input from user

name = input('Enter your name: ')

age = input('Enter your age: ')

print (name)

print (age)

Output:

Enter your Name: Dr. Brijesh Bakariya

Enter your age: 36

Dr. Brijesh Bakariya

36

Example 1.7:

# get input from a user

str1 = input()

# Getting input from a user without a prompt

print ('The inputted string 1 is: ', str1)

str2 = input('Enter a string: ')

#Getting input from the user with a prompt

print ('The inputted string is:', str2)

Output:

Dr. Brijesh Bakariya

The inputted string 1 is: Dr. Brijesh Bakariya

Enter a string:Dr. Krishna Kumar Mohbey

The inputted string 2is: Dr. Krishna Kumar Mohbey

Printing

It is the simplest way to display the output on the screen. Python has a print() method for output printing. We can pass zero or more print() function expression, but commas should separate the expressions. The print() function converts the expressions into a string before writing on the screen.

There is the following system of print() function.

Syntax: print(value(s), sep= ' ', end = '\n', file=file, flush=flush)

The value(s), sep, end, file, and flush are the parameters in which we can pass it. There are the following descriptions of these parameters:

value(s): Any value, and as many as you like. It will be converted to a string before printing.

sep='separator': (Optional) Specify how to separate the objects if there is more than one.Default:''.

end='end': (Optional) Specify what to print at the end.Default: '\n'.

file : (Optional) An object with a write method. Default:sys.stdout

flush : (Optional) A Boolean, specifying if the output is flushed (True) or buffered (False).

returns: It returns output to the screen.

Example 1.8:

# Use of print() function

print(Python is a programming language)

n1 = 10

# Two objects are passed

print (n1 =, 10)

n2 = n1

# Three objects are passed

print ('n1 =', n1, '= n2')

Output:

Python is a programming language

n1 = 10

n1 = 10 = n2

Example 1.9: The print() function with separator and end parameters:

n1 = 50

print (n1 =, n1, sep='000', end='\n\n')

print (n1 =, n1, sep='0', end='')

Output:

n1 =00050

n1 =050

Boolean

The bool() method is used to return or convert a value to a Boolean value, that is, True