Analytics

1. Lecture 3
Data Types & Operators
DA5120 – Programming for Business Analytics
Supun Gothama

2. Data Types

3. Introductions
• Data in Python can be of different types
• We will learn 3 basic types for now
− Numbers
− Strings
− Booleans

4. Numbers
• Four numeric types
− Integers (or “plain integers”) up to → int
− Long integers → long
− Floating-point (real) numbers → float
− Complex numbers → complex
• Integers can usually hold a value up to up to
• Long integers can have an unlimited size value

5. Numbers
• We can use Python’s type() function to check the
data type of a variable
>>> b = 97
>>> type(b)
<type 'int’>
>>> type(95.2)
<type 'float'>

6. Strings
• Strings are sequences of characters
• Anything inside quotes is considered a string in Python
• Can use single or double quotes
>>> s1 = "This is a string"
>>> s2 = 'This is also a string'
>>> type(s1)
<type 'str'>

7. Booleans
• The Boolean data types can only have 2 possible
values
− False
− True
• Behave according to Boolean algebra
>>> x = True
>>> type(x)
<type 'bool'>

8. Expressions &
Operators

9. Expressions
• Expressions combines literals, variables and
operators
− Eg: 3 + 5
• Produce a new value

10. Expressions
• Can be arbitrarily complicated
− 3 + 8 * 5 + 4 – 7 / 100
• Can be used in different places
− x = 3 + 7 / 5
− print(3 + 7 / 5)

11. Operators
• An operator is a symbol that tells Python interpreter to
perform specific mathematical, relational or logical
operation and produce a final result
• Operands are the values participate in an operation

12. Types of Operators
• We will learn the following types of operators in
Python
− Arithmetic Operators
− Comparison (Relational) Operators
− Assignment Operators
− Logical Operators

13. Arithmetic Operators
• You can add (+), subtract (-), multiply (*), and
divide (/) number in Python
>>> 2 + 3
5
>>> 3 - 2
1
>>> 2 * 3
6
>>> 3 / 2
1.5

14. Arithmetic Operators
• Exponent (**) operator performs exponential (power)
calculation on numbers
>>> 3 ** 2
9
>>> 3 ** 3
27
>>> 3 ** 4
81

15. Arithmetic Operators
• Modulus (%) operator divides left hand operand by
right hand operand and returns remainder
>>> 7 % 4
3
>>> 8 % 6
2
>>> 10 % 5
0

16. String Operators
• Concatenation (+) operator joins two strings
>>> "Abc" + "Xyz"
'AbcXyz'
• Repeat (*) operator repeats a string specified number
of times
>>> "Abc" * 3
'AbcAbcAbc'

17. Comparison Operators
• These operators compare the values on either sides and
give a Boolean result
• Equal (==) operator check whether the values of two
operands are equal
>>> 5 == 4
False
>>> 6 == 6
True

18. Comparison Operators
• Not equal (!= or <> ) operator check whether the values
of two operands are not equal
>>> 5 != 4
True
>>> 6 != 6
False
>>> 10 <> 26
True

19. Comparison Operators
• Greater than (>) operator check whether value of left
operand is greater than the value of right operand
>>> 5 > 4
True
>>> 6 > 6
False
• Less than (<) operator check whether value of left operand
is less than the value of right operand
>>> 5 < 4
False

20. Comparison Operators
• Python also has operators for
− Greater than or equal (>=)
− Less than or equal (<=)
>>> 6 >= 6
True
>>> 4 <= 9
True
>>> 4 >= 9
False

21. Logical Operators
• Logical operators are used to combine Boolean value
expressions and give a Boolean result
• and operator returns True if both operands are true
>>> True and True
True
>>> True and False
False
>>> False and False
False

22. Logical Operators
• or operator returns True if at least one of the operands is
true
>>> True or True
True
>>> True or False
True
>>> False or False
False

23. Logical Operators
• not operator inverts the Boolean value of the operand
>>> not False
True
>>> not True
False
• A truth table can be used to summarize
the results of these operators

24. Assignment Operators
• Assignment operators are used to assign values to
variables
• We already know the assign (=) operator
• Add and assign (+=) operator adds right operand to the left
operand and assign the result to left operand
− Eg: x += y is equivalent to x = x + y

25. Assignment Operators
• Similarly other arithmetic operations also can be used as
‘and assign’
Operator Example Equivalent to
+= x += 5 x = x + 5
-= x -= 5 x = x - 5
*= x *= 5 x = x * 5
/= x /= 5 x = x / 5
%= x %= 5 x = x % 5
**= x **= 5 x = x ** 5

26. Assignment Operators
x = 10
x += 4
print(x)
14
y = 20
y *= 5
print(y)
100

27. Operators with Expressions
• Operands for these operators does not have to be
simple values
• Operands can be any valid expressions
>>> 5 - 2 < 5 + 3
True
>>> 2 < 3 and 4 > 1
True
>>> not 2 < 3
False

28. Operator Precedence
• Expressions can be ambiguous
• Eg: a * 3 + b / x can be
− a * (3 + b) / x
− (a * 3) + (b / x)
− (a * 3 + b) / x
• To avoid this kind of ambiguity, python has a
precedence (priority) for operators

29. Operator Precedence
1. ** Exponentiation
2. +, - Unary plus and minus (eg: +5, -5)
3. *, / , % Multiply, divide, modulo
4. + , - Addition and subtraction
5. <=, < , >, >= Comparison operators
6. < >, ==, != Equality operators
7. = , %=, /=, //=, -=, +=, *=, **= Assignments
8. not, or, and Logical operators

30. Operator Precedence
• More than one operator exists in the same level
− These operators have the same precedence
− In that case almost all the operators are evaluated in left-
to-right order (associativity) in expression
• Example
− Multiplication and division have the same precedence
− Left operator is evaluated first
− 5 / 2 * 10 → 25.0

31. Operator Precedence
• Exponent operator ** has right-to-left associativity in Python
− 2 ** 3 ** 2 → 512
• Operator precedence can be changed using parentheses ()
as in mathematics
− (10 - 4) * 2 → 12
− 40 / (2 * 10) → 2.0

32. Evaluate the following
expressions.
Activity 1. 4 + 3 % 5
2. x = 10
x *= 2 ** 3
3. 2 * 3 > 6 and 10 < 20

33. Evaluate the following
expressions.
Activity 1. 4 + 3 % 5
→ 7
2. x = 10
x *= 2 ** 3
→ 80
3. 2 * 3 > 6 and 10 < 20
→ False

34. Summary
☑ Data types
☑ Expressions
☑ Operators
☑ Operator Precedence