Variables

Variables are an essential thing in all programming languages. They help us reuse multiple values more than just once.
One special thing about Python is the implicit type-inference. This means, that we do not have to assign a type to a variable by its declaration as in Java or C (although that is still possible, it's not required in Python). Basically, the compiler does the typing by itself.

Types in Python

Primitive Data Types

These following are called primitive, or, in other words, simple data types. Variables of these types can only hold one value.

• Integers
• Floats
• Strings
• Chars
• Complex numbers

Complex Data Types

• List
• Dictionary

Variable Name Rules

1. Variable names can only be alphanumeric (i.e. can only contain letters and whole numbers).
2. Variable names can only start with alphabetical letters or an underscore.
3. Variable names can not be any of the Python keywords (i.e. you can not assign a variable with the name "if").
4. Variable names are case-sensitive, so be sure that you're typing in the case you want.

Usage of variables

To assign a variable, we use this general Syntax:
variable_name = value

Now see some examples:

# declaring two strings
foo = 'foo'  
bar = 'bar'

# declaring an integer
# note: automatically inferred as integers
i1 = 7
i2 = 42

# declaring two floating point numbers
d1 = 42.7
d2 = 7.42

# declaring two complex numbers
c1 = 7 + 42j
c2 = 42 + 7j

Reuse of variables

The main thing about variables is that we can use them more than just one time by calling them. This is done as in the following example:

# defining a variable
foo = 'awesome'
# ... and reuse it by 
# printing it's value
print(foo)    #in Python 3.X
# print foo   #in Python 2.X