Variable in Python | ** Operator in Python | NameError in Python | int and float in Python |

With Python, it is possible to use the ** operator to calculate powers
print(5 ** 2)
print(5 * 5)
print(2 ** 7)

The equal sign (=) is used to assign a value to a variable. Afterwards, no result is displayed before the next interactive prompt:
width = 20
height = 5 * 9
print(width * height)

If a variable is not “defined” (assigned a value), trying to use it will give you an error:
print(n) # try to access an undefined variable
Traceback (most recent call last):
File "stdin", line 1, in module
NameError: name 'n' is not defined

In interactive mode, the last printed expression is assigned to the variable _. This means that when you are using Python as a desk calculator, it is somewhat easier to continue calculations, for example:
tax = 12.5 / 100
price = 100.50
tax_on_current_price = tax * price
answer = price + tax_on_current_price
print(answer)

Variable Names
A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). Rules for Python variables:
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 (age, Age and AGE are three different variables)
A variable name cannot be any of the Python keywords.

name = "devvrat" #True
my_name = "devvrat" #True
1name = "devvrat" #False
name1 = "devvrat" #True
name@ = "devvrat" #false

Camel Case
myName = "devvrat"
Pascal Case
MyName = "devvrat"
Snake Case
my_name = "devvrat"

Python is a cross-platform programming language, which means that it can run on multiple
platforms like Windows, macOS, Linux, and has even been ported to the Java and .NET virtual machines. It is free and open-source.

Let's create a very simple program called Hello World. A "Hello, World!" is a simple program that outputs Hello, World! on the screen. Since it's a very simple program, it's often used to introduce a new programming language to beginners.

Type the following code in any text editor or an IDE and save it as hello_world.py

Python is an easy to learn, powerful programming language. It has efficient high-level data structures and a simple but effective approach to object-oriented programming. Python’s elegant syntax and dynamic typing, together with its interpreted nature, make it an ideal language for scripting and rapid application development in many areas on most platforms.

The Python interpreter and the extensive standard library are freely available in source or binary form for all major platforms from the Python web site, https://www.python.org/, and may be freely distributed. The same site also contains distributions of and pointers to many free third party Python modules, programs and tools, and additional documentation.

The Python interpreter is easily extended with new functions and data types implemented in C or C++ (or other languages callable from C). Python is also suitable as an extension language for customizable applications.

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Simply All You Need
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Intelligent Python Assistance
PyCharm provides smart code completion, code inspections, on-the-fly error highlighting and quick-fixes, along with automated code refactorings and rich navigation capabilities.

Web Development Frameworks
PyCharm offers great framework-specific support for modern web development frameworks such as Django, Flask, Google App Engine, Pyramid, and web2py.

Scientific Tools
PyCharm integrates with IPython Notebook, has an interactive Python console, and supports Anaconda as well as multiple scientific packages including matplotlib and NumPy.

Cross-technology Development
In addition to Python, PyCharm supports JavaScript, CoffeeScript, TypeScript, Cython, SQL, HTML/CSS, template languages, AngularJS, Node.js, and more.

Even though most of today's Linux and Mac have Python pre-installed in it, the version might be out-of-date. So, it is always a good idea to install the most current version.

The Easiest Way to Run Python
The easiest way to run Python is by using PyCharm.