Variable

Variable Declaration

To declare variables in Python:

							
# assign the integer value 3 to the variable a
>>> a = 3
 
# assign the decimal value 4.0 to the variable b      
>>> b = 4.0 
  
# assign the string '1' to the variable c  
>>> c = '1'
    
# adding two numbers
>>> a + b    
7.0

# adding number and string (This is not allowed and will produce an error)
>>> a + c       	
						

Commonly used data types include int, float, str and bool. To determine the datatype of a variable:

>>> a = 3
>>> type(a)
<type 'int'>

>>> b = 4.0
<type 'float'>

>>> c = 'hello'
>>> type(c)
<type 'str'>

>>> d = True
>>> type(d)
<type 'bool'>	
						

Data Type Conversion

Use the following functions for conversion between data types: float(x),int(x), str(x)

>>> a = 5           # int
>>> b = float(a)    # convert to float
>>> b
5.0

>>> c = str(a)      # convert to string
>>> c
'5'

>>> d = int(4.6)    # convert to int, take note of the round down
>>> d
4
						

Mathematical operations

For numbers, the usual mathematical rules apply. You can use any of the following operations: *, /, +, - on numbers. Take note of the division operator.

>>> 1/2     # returns integer value
0
>>> 1/2.0   # returns decimal value
0.5
						

Take note of the following operations on string

>>> '1' + '2'   # concatenation instead of addition
'12'

>>> '1' * 5     # This is valid in Python
'11111'
						

Summary of Mathematical Operators

Symbols	Operations	Examples	Outputs
+	Addition	a = 1+2	3
-	Subtraction	a = 2-1	1
*	Multiplication	a = 2*2	4
/	Division	a = 5.0/2	2.5
//	Truncating Division	a = 5.0//2	2.0
%	Modulo	a = 5%2	1
**	Power	a = 5**2	25

Code Snippets

This section will contain some code snippets to show some practical use of the topic that you have learnt.

# Swapping of variable
# ---------------------
>>> a = 3
>>> b = 4
>>> a, b
(3, 4)

# doing the swap
>>>a, b = b, a 
>>> a, b
(4, 3) # values swapped


# Checking for even number
# ------------------------
>>> a = 6

# if the remainder of 'a' dividing by 2 is 0, 'a' is even number
>> a % 2 == 0
True