If you are interested to learn about the python introduction

What is a syntax in Python?

The syntax of the Python programming language is the set of rules that defines how a Python program will be written and interpreted (by both the runtime system and by human readers). The Python language has many similarities to Perl, C, and Java.

Execute Python Syntax

As we learned in the previous page, Python syntax can be executed by writing directly in the Command Line:

>>> print("Hello, World!")
Hello, World!

Or by creating a python file on the server, using the .py file extension, and running it in the Command Line:

C:\Users\Your Name>python myfile.py

Python Indentation

Indentation refers to the spaces at the beginning of a code line. Where in other programming languages the indentation in code is for readability only, the indentation in Python is very important. Python uses indentation to indicate a block of code.

Example

if 5 > 2:
  print("Five is greater than two!")

Python will give you an error if you skip the indentation

Example

Syntax Error:

if 5 > 2:
print("Five is greater than two!")

The number of spaces is up to you as a programmer, the most common use is four, but it has to be at least one.

Example

if 5 > 2:
 print("Five is greater than two!") 
if 5 > 2:
        print("Five is greater than two!") 

You have to use the same number of spaces in the same block of code, otherwise Python will give you an error:

Example

Syntax Error:

if 5 > 2:
 print("Five is greater than two!")
        print("Five is greater than two!")

Python Variables

In Python, variables are created when you assign a value to it:

Example

Variables in Python:

x = 5
y = "Hello, World!"

Python has no command for declaring a variable.

You will learn more about variables in the Python Variables chapter.

Comments

Python has commenting capability for the purpose of in-code documentation. Comments start with a #, and Python will render the rest of the line as a comment:

Example

Comments in Python:

#This is a comment.
print("Hello, World!")

Python Getting Started

Python Install

Many PCs and Macs will have python already installed.

To check if you have python installed on a Windows PC, search in the start bar for Python or run the following on the Command Line (cmd.exe):

C:\Users\Your Name>python --version

To check if you have python installed on a Linux or Mac, then on linux open the command line or on Mac open the Terminal and type:

python --version

If you find that you do not have Python installed on your computer, then you can download it for free from the following website: 

Python Quickstart

Python is an interpreted programming language, this means that as a developer you write Python (.py) files in a text editor and then put those files into the python interpreter to be executed. The way to run a python file is like this on the command line:

C:\Users\Your Name>python helloworld.py

Where “helloworld.py” is the name of your python file. Let’s write our first Python file, called helloworld.py, which can be done in any text editor.

helloworld.py

print("Hello, World!")

Simple as that. Save your file. Open your command line, navigate to the directory where you saved your file, and run:

C:\Users\Your Name>python helloworld.py

The output should read:

Hello, World!

Congratulations, you have written and executed your first Python program.

The Python Command Line

To test a short amount of code in python sometimes it is quickest and easiest not to write the code in a file. This is made possible because Python can be run as a command line itself. Type the following on the Windows, Mac or Linux command line:

C:\Users\Your Name>python

Or, if the “python” command did not work, you can try “py”:

C:\Users\Your Name>py

From there you can write any python, including our hello world example from earlier in the tutorial:

C:\Users\Your Name>python
Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hello, World!")

Which will write “Hello, World!” in the command line:C:\Users\Your Name>python

C:\Users\Your Name>python
Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hello, World!")
Hello, World!

Whenever you are done in the python command line, you can simply type the following to quit the python command line interface:

exit()

Python Identifiers

A name in python program is called Python identifier. It can be variable, class, function and module or and other object. 

Rules to define identifiers in Python:

The only allowed characters in Python are alphabet symbols (either lower case or upper case) digits (0 to 9) underscore symbol (_) followed by zero or more letters. By mistake if you are using any other symbol like $, @, and % then we will get syntax error. Identifier should not starts with digit. Python programming language is case sensitive language total and TOTAL are two different identifiers in python.

Best Practices for python Identifiers

• If Identifier is start with Underscore (_) then it indicates it is private.
• Identifier should not start with Digits.
• We cannot use reserved words as identifiers.
• There is no length limit for Python identifiers. But not recommended to use too lengthy identifiers.

Reserved Words

In Python some words are reserved to represent some meaning or functionality. Such type of words are called Reserved words. There are 35 reserved words available in Python.

All Reserved words in Python contain only alphabet symbols.

Except the following 3 reserved Upper case words all contain only lower case alphabet only.

• True
• False
• None

If you want to check all reserved words

Python inbuilt function which you can use like this 

import keyword 
keyword.kwlist 

You can see output like this:

['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']

Summary :-

In this tutorial, we have learned about the python syntax, how to run python script on windows, what is python indentation, quotation, comments, python identifiers and reserved words.