Python is a popular programming language. It was created by Guido van Rossum, and released in 1991.

• Python can be used on a server to create web applications.
• Python can be used alongside software to create workflows.
• Python can connect to database systems. It can also read and modify files.
• Python can be used to handle big data and perform complex mathematics.
• Python can be used for rapid prototyping, or for production-ready software development.

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 Variables

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

Example

x = 5
y = "Hello, World!"

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

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

Variables are containers for storing data values. Unlike other programming languages, Python has no command for declaring a variable. A variable is created the moment you first assign a value to it.

Example

x = 5
y = "John"
print(x)
print(y)

Variables do not need to be declared with any particular type and can even change type after they have been set.

A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume).

Example

• 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)

Python has the following data types built-in by default, in these categories:

• Text Type: str
• Numeric Types: int, float, complex
• Sequence Types: list, tuple, range
• Mapping Type: dict
• Set Types: set, frozenset
• Boolean Type: bool
• Binary Types: bytes, bytearray, memoryview

In Python, the data type is set when you assign a value to a variable.

Python supports the usual logical conditions from mathematics. Python relies on indentation (whitespace at the beginning of a line) to define scope in the code. Other programming languages often use curly-brackets for this purpose.

An "if statement" is written by using the if keyword. The elif keyword is pythons way of saying "if the previous conditions were not true, then try this condition". The else keyword catches anything which isn't caught by the preceding conditions.

Example

a = 200
b = 33
if b > a:
  print("b is greater than a")
elif a == b:
  print("a and b are equal")
else:
  print("a is greater than b")

If you have only one statement to execute, one for if, and one for else, you can put it all on the same line. This technique is known as Ternary Operators, or Conditional Expressions.

Example

a = 2
b = 330
print("A") if a > b else print("B")

With the while loop we can execute a set of statements as long as a condition is true. It's important to increment i, or else the loop will continue forever. The while loop requires relevant variables to be ready, in this example we need to define an indexing variable, i, which we set to 1.

Example

Print i as long as i is less than 6:

i = 1
while i < 6:
  print(i)
  i += 1

A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string). This is less like the for keyword in other programming languages, and works more like an iterator method as found in other object-orientated programming languages. With the for loop we can execute a set of statements, once for each item in a list, tuple, set etc.

Example

Print each fruit in a fruit list:

fruits = ["apple", "banana", "cherry"]
for x in fruits:
  print(x)

A function is a block of code which only runs when it is called. You can pass data, known as parameters, into a function. A function can return data as a result.

In Python a function is defined using the def keyword.To call a function, use the function name followed by parenthesis.

Example

def my_function():
  print("Hello from a function")
  
my_function()

Information can be passed into functions as arguments. Arguments are specified after the function name, inside the parentheses. You can add as many arguments as you want, just separate them with a comma. The following example has a function with one argument (fname). When the function is called, we pass along a first name, which is used inside the function to print the full name:

Example

def my_function(fname):
  print(fname + " Refsnes")

my_function("Emil")
my_function("Tobias")
my_function("Linus")

There are four collection data types in the Python programming language:

• List is a collection which is ordered and changeable. Allows duplicate members.

  thislist = ["apple", "banana", "cherry"]
  print(thislist)

• Tuple is a collection which is ordered and unchangeable. Allows duplicate members.

  thistuple = ("apple", "banana", "cherry")
  print(thistuple)

• Set is a collection which is unordered and unindexed. No duplicate members.

  thisset = {"apple", "banana", "cherry"}
  print(thisset)

• Dictionary is a collection which is unordered, changeable and indexed. No duplicate members.

  thisdict = {
    "brand": "Ford",
    "model": "Mustang",
    "year": 1964
  }
  print(thisdict)

Some additional information here Python is an object oriented programming language. Almost everything in Python is an object, with its properties and methods. A Class is like an object constructor, or a "blueprint" for creating objects.

Create a class named MyClass, with a property named x:

class MyClass:
  x = 5

Create an object named p1, and print the value of x:

p1 = MyClass()
print(p1.x)

All the documentation in this page is taken from w3schools.

You can read more about Python on the Python.org.