- CPython- Written in C

- Jython- Written in Java

- IronPython- Implemented in C#

- Brython- Browser Python

- RubyPython- Bridge between Python and Ruby interpreters

- PyPY- Implemented in Python

- MicroPython- Runs on a microcontroller

- .py

- .pyc

- .pyd

- .pyo

- .pyw

- .pyz

To learn about variables, operators, and other topics, refer to the links above. Here, we will talk about the syntax of Python code.

- Line Structure - Programs consist of logical lines. Each line has a NEWLINE token at the end. Blank lines are ignored.

- Multiline statements - There are no semicolons or braces in Python (you can use semicolons if you want, but they are not mandatory)

- Backward slash - To distribute a statement across multiple lines.

- Triple quotes - Put strings in triple quotes to span them across multiple lines.

- Comments - They explain code and are ignored by the interpreter. Declared by hash (#).

- Docstrings - Documentation strings that explain code. Retained at runtime for inspection.

- Indentation - Since there are no curly braces, you need to indent code blocks equally. You can use tabs or spaces, but not a combination of both. PEP8 recommends using 4 spaces.

- Multiple statements in one line - You can use semicolons to separate multiple statements in one line. You can also put an if-statement’s single-line body in one line.

- Quotations - You can delimit strings with single or double quotes, but not both (opening with one and closing with another). If you use single quotes inside the string, use double quotes to delimit. You can escape quotes inside strings with the escape character (\).

- Identifiers - These are names of elements, and are case-sensitive. You need to follow some rules when naming identifiers.

- Variables - They hold values. Python follows duck-typing and is dynamically-typed. You don’t need to declare the type of variable, that is determined by the interpreter at runtime.

- String formatters - For this, you can use the % operator, the format() method, or f-strings.

- Python vs Java vs C++ - Curly braces are mandatory in Java and C++, but Python uses whitespace indentation to delimit code. Semicolons are optional in Python, but can cause errors in C++ and Java. Python is dynamically-typed, Java and C++ are statically-typed. Java is faster than Python.

While you’re learning Python, you will use an IDE (Integrated Development Environment) to run the code. You can choose one or more of the following. Here, you can write, edit, test and debug code. It has build automation, code linting, testing, and debugging. This speeds up your work.

Pricing: Free

IDLE comes with Python. It is lightweight and simple.

Pricing: Freemium

Sublime Text 3 is a popular code editor and also supports other languages. It is fast, customizable, and has a large community. It has packages available for debugging, auto-completion, and code linting, and for Django, Flask, and scientific development.

Pricing: Free

Atom is an editor by GitHub and is open-source. It is customizable and has packages like autocomplete-python, linter-flake8, and python-debugger.

Pricing: Free

VS Code is a free and open-source IDE by Microsoft. It has features like intelligent code completion, linting for potential errors, debugging and unit testing, and you can add extensions. It is also lightweight.

Pricing: Free

The VIM text editor comes preinstalled in MacOS and UNIX, and is available for Windows. It has keyboard shortcuts and is extendible. It also has plugins for syntax highlighting, code completion, debugging, and refactoring.

Pricing: Free

This is an open-source IDE and can be installed with Anaconda. It has features like autocompletion, debugging, and iPython shell.

Pricing: Free

This is an online compiler- you don't need to install Python and set up an environment with this. It also has support for other languages.

Pricing: Free

JupyterLab is the next-gen UI for Project Jupyter. It has all the building blocks of the Jupyter Notebook, like notebooks, terminal, text editor, file browser, and rich output. The UI is flexible.

Pricing: Free

PyDev is a Python IDE for Eclipse. Using the PyDev plugin with Eclipse, we can develop for Python.

Python is an easy language to learn and has a smooth learning curve. Learning the basics will not take much time. But you will need to practice as you learn. The more you practice, the better you are at it. You will need to build projects as well. Once you have followed the steps mentioned above, you can say you know Python. So how long it will take depends on you.

Python has over 198,495 projects in the PyPI. Which of those packages (and the built-in ones) should you learn? Here are a few names:

- scipy

- numpy

- matplotlib

- urllib

- requests

- smtplib

- os

- shutil

- tkinter

- PyQt

- threading

- subprocess

- PyMySQL

- unittest

- pickle

- logging

- virtualenv

- pandas

- scikit-learn

- datetime, calendar, time

- collections

- array

- itertools

Building a project will strengthen your basics and help you figure out what you don’t know.

- Start with some basic projects like Hangman and Tic-Tac-Toe. Build an alarm clock. This can be console-based.

- Move on to intermediate projects like a todo-list with Django. Use frameworks and build GUIs too.

- Now, it’s time to work on some advanced projects like:

- Parkinson’s Disease Detection

- Speech Emotion Recognition

- Breast Cancer Classification

- Fake News Detection

- Gender and Age Detection

- Driver Drowsiness Detection

You can also build a project to solve a real problem you face or faced earlier.

There is no official certified exam for Python. DataFlair offers an excellent certification program for Python. This has more than 20 hours of video-based sessions, multiples practicals, and 5 exciting projects to build- with complete source code!

You are now ready to answer some interview questions at any level- beginner, intermediate, or advanced. You can also do this after any of the previous steps. Refer to these questions- these are questions of all difficulties- beginner, intermediate, and advanced. They also have some open-ended questions.

- Top 150+ Interview Questions for Freshers

- Python Interview Questions for Intermediate

- Python Interview Questions - Advanced

Python is the second-most loved language and the most-wanted language according to the StackOverflow Developer Survey for 2019. It seems to have a good future with stable jobs. Also, the jobs pay well. Here are the profiles you can go for if you learn Python:

- Software Engineer

- Senior Software Engineer

- DevOps Engineer

- Data Scientist

- Senior Data Scientist

And here are the salaries:

- Software Engineer - $103,035 /year

- Senior Software Engineer - $129,328 /year

- DevOps Engineer - $115,666 /year

- Data Scientist - $117,345 /year

- Senior Data Scientist - $136,633 /year

Python is at #3 on the TIOBE Index for September 2019. Job boards like Naukri and Indeed post more than 16000 to 24000 jobs for Python. Right now, there is a high demand, but low supply. This is a great opportunity for you. There is a large number of jobs per Python programmer.

One reason why Python is so popular is its libraries. We have many libraries geared toward data science and machine learning. These have tools and functions/methods for trivial tasks so we don’t have to implement everything from scratch. You should learn to work with the following libraries:

- scikit-learn

- scipy

- numpy

- pandas

- xgboost

- keras

- tensorflow

- matplotlib

- seaborn

- theano

- mlpy

- NetworkX

- SymPy

- Dask

- Dmelt

- PyBrain

***What Next***

- Learn Python for Machine Learning

- Learn Python for Data Science

- Learn Python for Artificial Intelligence

Many giant companies use Python for their products and services. Some of these are:

- Google - Python as a major programming language

- Facebook - For production engineering

- NASA Workflow Automation Tool - Written in Python

- Nokia - Platforms like S60

- IBM - Factor tool control applications

- Walt Disney Feature Animation - Scripting language for animation

- Yahoo! Maps services - Written in Python

- Disqus - Commenting forum built with Django

- Dropbox stack - Written in Python

- Quora - Social website written in Python

- Instagram - Built with Django

- YouTube - Scripted Python for website

- Bit Torrent - Originally written in Python

- Other companies like Uber, MIT, Hike, Pandora, Spotify, Udemy, Netflix, PayPal, Reddit, Pinterest, and Glassdoor use it too

Netflix uses Python for data analysis and its backend services. It is how it recommends new titles. Netflix also uses Python to build custom extensions to the Jupyter server. This can be used to manage tasks like logging, archiving, publishing and cloning notebooks. Netflix uses the statistical and numerical libraries like numpy, scipy, tuptures, and pandas. It also uses Python for automation, data exploration, and visualization. It implements demand engineering, insight engineering, Open Connect Network, Information Security, an ML infrastructure, Notebooks, a Partner Ecosystem, and Animation and NVFX.

Like Netflix, Spotify uses Python for data analysis and backend services. It uses ZeroMQ for backend communication- this is an open networking framework written in Python and C++. Python allows fast development. Also, Spotify uses it for data analytics to create suggestions and recommendations. It also uses Luigi for synchronization with Hadoop. This lets it create "Radio and Discovery".

Quora is a social networking platform with questions and answers. They considered many languages before choosing Python because it has no type checking, and is slow. They rejected C# because the Microsoft Language is proprietary. Java has strict syntax, so it was rejected. So, like Google, Quora chose Python for its ease of writing and readability. They solved the problem of type checking by writing unit tests. They also liked the frameworks for Python- Django and Pylons. It was also easier to club Python and JS for handling user interactions.

Facebook extensively uses Python. The libraries and frameworks reduce the code-load and focus on improvements. Facebook used Python for multiple services in infrastructure management, and made it scale-efficient. It also published Py3 written projects, including Facebook Ads API and a Python async IRC bot framework.

Google has been using Python since the beginning. They decided to implement Python for ease of maintenance and faster delivery than C++. They also recoded some Perl or Bash scripts into Python. Python is the official Google server-side language at Google. Peter Norvig, and American computer scientist, said "Python has been an important part of Google since the beginning and remains so as the system grows and evolves. Today, dozens of Google engineers use Python, and we're looking for more people with skills in this language."

This was the A-Z of Python. We tried to cover everything you could want to know. We discussed Python, its syntax, why and how to learn, a short tutorials, some libraries, names of projects, interview questions, its future, Python for Machine Learning, companies and some case studies.