To create a variable in Python, all you need to do is specify the variable name, and then assign a value to it.

<variable name> = <value>

Python uses = to assign values to variables. There’s no need to declare a variable in advance (or to assign a data type to it), assigning a value to a variable itself declares and initializes the variable with that value. There’s no way to declare a variable without assigning it an initial value.

# Integer
a = 2
print(a)
# Output: 2

# Integer    
b = 9223372036854775807
print(b)
# Output: 9223372036854775807

# Floating point
pi = 3.14
print(pi)
# Output: 3.14

# String
c = 'A'
print(c)
# Output: A

# String    
name = 'John Doe'
print(name)
# Output: John Doe

# Boolean    
q = True
print(q)
# Output: True

# Empty value or null data type
x = None
print(x)
# Output: None

Variable assignment works from left to right. So the following will give you an syntax error.

0 = x
=> Output: SyntaxError: can't assign to literal

You can not use Python’s keywords as a valid variable name. You can see the list of keywords by:

import keyword
print(keyword.kwlist)

Rules for variable naming:

1. Variables names must start with a letter or an underscore.

   x  = True   # valid
   _y = True   # valid
   
   9x = False  # starts with numeral 
   => SyntaxError: invalid syntax   
   
   $y = False #  starts with symbol 
   => SyntaxError: invalid syntax
   

2. The remainder of your variable name may consist of letters, numbers and underscores.

   has_0_in_it = “Still Valid”

3. Names are case sensitive.

   x = 9  
   y = X*5   
   =>NameError: name 'X' is not defined
   

Even though there’s no need to specify a data type when declaring a variable in Python, while allocating the necessary area in memory for the variable, the Python interpreter automatically picks the most suitable built-in type for it:

a = 2
print(type(a))
# Output: <type 'int'>

b = 9223372036854775807
print(type(b))
# Output: <type 'int'>

pi = 3.14
print(type(pi))
# Output: <type 'float'>

c = 'A'
print(type(c))
# Output: <type 'str'>

name = 'John Doe'
print(type(name))
# Output: <type 'str'>

q = True
print(type(q))
# Output: <type 'bool'>

x = None
print(type(x))
# Output: <type 'NoneType'>

Now you know the basics of assignment, let’s get this subtlety about assignment in python out of the way.

When you use = to do an assignment operation, what’s on the left of = is a name for the object on the right. Finally, what = does is assign the reference of the object on the right to the name on the left.

That is:

a_name = an_object  # "a_name" is now a name for the reference to the object "an_object"

So, from many assignment examples above, if we pick pi = 3.14, then pi is a name (not the name, since an object can have multiple names) for the object 3.14. If you don’t understand something below, come back to this point and read this again! Also, you can take a look at this for a better understanding.