The Ultimate Python Beginner’s Guide

Python is an interpreted, high-level programming language. The language and object-oriented approach aim to help the programmers to write exact, logical code for small and large-scale projects.

Table of Contents

Why Should You Learn Python?

Python is one of the programming languages that is loved by developers, data scientists, software engineers, and hackers because of its flexibility, versatility and object-oriented features. Many of the mobile and web applications we enjoy today is because of Python’s great libraries, various frameworks, vast collections of modules, and file extensions. Not only that, but Python is also great for building micro-project to macro enterprise web services as well as for supporting other types of programming languages.

Although it’s a high-level language and can do complex tasks, Python is easy to learn and has a clear syntax. Therefore, it’s recommended for both beginners and experienced programmers. Also, there are plenty of ways to learn Python; you can do self-study, enroll yourself in a coding boot camp or school, or watch online tutorials.

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Features

  • Open Source and Free

Python is an open-source programming language, that means anyone can create and contribute to its development. Python has an online forum where many coders gather daily to improve this language further. Along With this, Python is free to download and can be used in any operating system, be it Windows, Mac, or Linux.

  • Integrated by Nature

Python is integrated by nature. It means that a python interpreter executes codes line by line. Unlike other object-oriented languages, you don’t need to compile Python code, making the debugging process much more comfortable and efficient. Another advantage of this is that while execution, the Python code is immediately converted into an intermediate form, which is also known as byte-code, which makes it easier to execute and also saves runtime in the long run.

  • Support for GUI

Graphical User Interface is one of the critical aspects of any programming language because it can add flair to code and make the results more visual. Python supports a wide array of GUIs that can easily be imported to the interpreter, making this one of the most favorite languages for developers.

  • Highly Portable

If you are running python on the windows and you need to shift the same to either a Mac or a Linux system, you can quickly achieve the same in Python without worrying about changing the code. This is not possible in other programming languages, making Python one of the most portable languages available.

  • Object-Oriented Approach

One of the critical aspects of Python is its object-oriented approach. This means that Python recognizes the concept of class and object encapsulation, thus allowing programs to be efficient in the long run.

Applications of Python

  • Business applications

Business Applications differ from other standard applications. ERP and E-commerce are few examples of a business application. This kind of application requires scalability, extensive readability, and Python provides all these features.

Oddo is an example of the Python-based application which offers a range of business applications. Python provides a platform to develop the business application.

  • Numeric and Scientific
    In today’s world of Artificial intelligence where the machine can perform the task. Python is the most suitable language for Artificial intelligence. It consists of mathematical libraries and many scientific, which makes it easy to solve complex calculations. Implementing machine learning algorithms requires mathematical calculation. Python has several libraries for scientific and numeric such as Numpy, Scikit-learn, Scipy etc. If you have some  knowledge of Python, you can import libraries on the top of the code. Few popular frameworks of machine libraries are given below.
  • SciPy
  • Scikit-learn
  • NumPy
  • Pandas
  • Matplotlib
  • Console based application

Console-based applications run from the command-line. These applications are computer programs which use commands to execute. This kind of application is more popular in the old generation of computers. Python can develop this kind of application effectively and efficiently. It is famous for having the Read-Eval-Print Loop that makes it a suitable language for the command-line applications.

Python provides a free library or module which helps you to build the command-line apps. The libraries are used to read and write. There are advanced libraries that can develop independent console apps.

  • Web Applications

You can use Python to develop web applications. It provides libraries to handle internet protocols like XML and HTML, JSON, Email processing, request, beautiful soup, Feedparser, etc. One of Python’s frameworks, Django is used on Instagram. Python provides many useful frameworks, and these are mentioned below:

  • Plone and Django CMS (Advance Content management
  • Django and Pyramid framework(Use for heavy applications)
  • Flask and Bottle (Micro-framework)
  • Image Processing applications

Python contains libraries that are used to work with the image. The image can be manipulated according to your requirements. Some libraries of image processing are mentioned below.

  • OpenCV
  • Pillow
  • SimpleITK

Environment Setup

Python is available on various platforms, which includes Linux, Windows and Mac OS X. Let us understand how to set up the Python environment.

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Local Environment Setup

Open the terminal window and type “python” to find out if it is already installed and which version is installed.

  • Macintosh (Intel, PPC, 68K)
  • Unix (Solaris, Linux, AIX,FreeBSD, HP/UX, SunOS, IRIX, etc.)
  • Win 9x/NT/2000
  • Nokia mobile phones
  • OS/2
  • Amiga
  • DOS (multiple versions)
  • PalmOS
  • Windows CE
  • Acorn/RISC OS
  • BeOS
  • VMS/OpenVMS
  • QNX
  • VxWorks
  • Psion

How to get Python

You will find an up-to-date and source code, binaries, documentation, news, etc., on the official website of Python https://www.python.org/

You can also download Python documentation from https://www.python.org/doc/. The documentation is available in PDF,HTML and PostScript formats.

How to install Python

Python distribution is available for various platforms. You have to download only the binary code that is applicable for your platform and install Python.

If the binary code for the platform is not available, you need a C compiler to compile the code manually. Compiling the code offers more flexibility in terms of choice of features that you require in your installation.

Windows Installation

Here are the steps you need to follow to install Python on Windows.

  • Open the Web browser and go to https://www.python.org/downloads/.
  • Now follow the link for the Windows installer python-XYZ.msi file, and you will find the XYZ version you need to install.
  • To use this installer, Windows must support Microsoft Installer 2.0. Save the installer to your system and then run it to find out if your device supports MSI.
  • Run the downloaded file. This will bring up the Python install wizard, which is relatively easy to use. Accept the default settings, wait until the installation is finished, and you are done.

Unix/Linux Installation

Here are some simple steps to install Python on a Unix/Linux machine.

  • Open the Web browser and go to https://www.python.org/downloads/.
  • Now go to download zipped source code available for Unix/Linux.
  • Download and extract files.
  • Edit the modules/setup file if you want to customize some options.
  • run/configure script
  • install

This installs Python at standard location /usr/local/bin and its libraries at /usr/local/lib/pythonXX where XX is the version of Python.

MAC Installation

Recent MAC comes with Python installed, but you need to update it. Go to http://www.python.org/download/mac/ for getting the current version along with some extra tools to support development. 

You can have full access to the complete documentation at this website − http://www.cwi.nl/~jack/macpython.html.

Setting up Path for Python

Programs and other files can be in many directories, so OS provides a search path that lists directories that the OS searches for execution.

It is stored in an environment variable, which is maintained by the operating system. The variable contains information of the command shell and other programs.

The path variable is named as PATH in Unix (Unix is case sensitive) or Path in Windows (Windows is not case sensitive).

In Mac, installer handles the path details. To invoke the Python interpreter, you must add the Python directory to your path.Setting path for Unix/Linux

To add the directory to the path for Unix/Linux −

  • In the csh shell-type setenv PATH “$PATH:/usr/bin/python” , press Enter.
  • In the bash shell − type export PATH=”$PATH:/usr/bin/python” and press Enter.
  • In the Ksh shell-type PATH=”$PATH:/usr/bin/python”, press Enter.
  • Note − /usr/bin/python is the path of the Python directory

Setting path for Windows

To add the directory to the path for Windows −

At the command prompt − type path %path%;C:\Python and press Enter.

Note − C:\Python is the path of the Python directory.

Python Environment Variables

S.NoVariableDescription
1PYTHONPATHIt has a similar role as PATH. This variable tells the interpreter where to locate the module files that are imported into a program. It should include the Python library directory and the directories having Python source code. The Python installer sometimes presets PYTHONPATH.
2PYTHONCASEOKIt is used in Windows to tell Python to find the first case-insensitive match in an import statement. Set the variable to any value to activate it.
3PYTHONSTARTUPIt contains the path of the initialization file with Python source code. It is executed every time you start the interpreter. It is named as .pythonrc.py in Unix, and it has commands that load utilities or modify PYTHONPATH.
4PYTHONHOMEIt is a module search path. It is embedded in the PYTHONPATH or PYTHONSTARTUP directories to make switching module libraries easy.

Running Python

There are different ways to start Python. You can start Python from Unix, DOS, or any other system that provides you with a command-line interpreter or shell window. Enter Python the command line.

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Start coding right away in the interactive interpreter.

We already have set up a programming environment for python online so that you can execute all the available examples. Feel free to modify the models and run it online.

Basic Syntax

Just like other natural languages, a computer programming language comprises a set of predefined words called keywords. A predefined rule of usage for each keyword is called syntax. Python interpreter has 33 keywords defined in it. Since they have a predefined meaning, they cannot be used for any other purpose. The list of Python keywords are obtained by using the following help command in the Python shell.

True elif intry 
False raisedefif 
None del returnimport
andwhileiselse
as except lambdawith
break for not class
from orcontinue pass
global assertyieldnonlocal 
finally 

Except False, None and True the other keywords are entirely in lowercase.

Python Identifiers

Apart from keywords, the Python program also has functions, variables, modules, classes, packages, etc. The identifier is the name given to the programming elements. The identifier should start with either an alphabet letter (upper or lower case) or an underscore (_). After that, more than one alphabet letter (A-Z or a-z), digits (0-9). No other characters are allowed.

  • The name of the class starts with an uppercase alphabet letter. Others begin with lowercase alphabet letters.
  • One or two underscore characters have a unique sense when naming the instance attributes of the class. 
  • Two trailing and leading underscores are used in the language for a special purpose. For example (e.g. __add__, __init__)

Python Statement

By default, the Python interpreter treats a text terminated by a hard carriage return (newline character) as a statement. This means each line in a Python script is a statement. (Just as in C++/C#, a semicolon; denotes the end of a statement).

Although, you can show the text spread over more than one line to be a single statement using the backslash (\) as a continuation character.

Use the semicolon; to write the multiple statements in a single line.

Indents in Python

At times it is required to construct a block of more than one statement. 

Different programming languages use various techniques to define the scope and extent of a block of statements in constructs like class, function, conditional, and loop. In C, C++, C#, or Java, words inside the brackets { and } are treated as a block.

Python uses uniform indentation to indicate a block of statements. When a block is started, type the colon symbol (:) and press Enter. 

Any Python editor (like IDLE) goes to the next line leaving whitespace. The following statements in the block follow the same level of indentation. To notify the end of a block, the whitespace is reduced by pressing the backspace key. 

If your editor is not built for Python, you need to ensure that a block’s statements should have the same indentation level by pressing the tab or spacebar key. The Python interpreter will show an error if the indentation level is not the same.

The Python shell, SayHello() function block started after: and press Enter. It is then displayed to mark the block. Now, use tab for indentation and then write a statement. Now to end the block, press Enter two times.

Comments in Python

In the Python script, the symbol # indicates the beginning of a comment line. It is effective until the end of the line in the editor. If # is the first character in the line, then the entire line is a comment. It can also be used in the middle of a line.

In Python, there is no rule to write multi-line words or a block comment. Each line must have the # symbol at the start to be marked as a comment. A lot of Python IDEs have shortcuts to keep a block of statements as a comment.

A triple multi-line string is also treated as a comment if it is not a docstring of a function or a class.

Getting Input

The input function is a part of the library of standard Python distribution. It reads the keystrokes as a string object, referred to by a variable having a proper name.

The input() function reads the input as a string, even if it comprises digits. The type() function used earlier confirms this behavior.

Display the Output

Another in-built function, print() serves as an output statement in Python. It echoes the value of any Python expression on the Python shell. Multiple values are displayed by the single print() function separated by a comma. The following example demonstrates values of name and age variables using the available print() function.