Python: Arithmetic and Assignment Operators

Python Operators Overview

• Python operators are categorized into arithmetic, assignment, comparison, logical, bitwise, identity, and membership groups
• Operator precedence dictates the order in which operations are performed, with multiplication and division taking priority over addition and subtraction

Arithmetic Operators

• These operators perform common mathematic operations using numeric values
• Addition (+) adds two values, e.g., x + y
• Subtraction (-) subtracts one value from another, e.g., x - y
• Multiplication (*) multiplies two values, e.g., x * y
• Division (/) divides one value by another, e.g., x / y
• Modulus (%) gives the remainder of a division, e.g., x % y
• Floor division (//) returns the integer part of the division, e.g., x // y
• Exponentiation (**) raises a number to a power, e.g., x ** y

Assignment Operators

• Assignment operators assign values to variables
• The assignment operator (=) assigns a value, e.g., x = y
• Addition assignment (+=) adds a value and assigns it to the variable, e.g., x += y is equivalent to x = x + y
• Subtraction assignment (-=) subtracts a value and assigns it to the variable, e.g., x -= y is equivalent to x = x - y
• Multiplication assignment (*=) multiplies a value and assigns it to the variable, e.g., x *= y is equivalent to x = x * y
• Division assignment (/=) divides a value and assigns it to the variable, e.g., x /= y is equivalent to x = x / y
• Modulus assignment (%=) calculates the modulus and assigns it, e.g., x %= y is equivalent to x = x % y
• Floor division assignment (//=) performs floor division and assigns it, e.g., x //= y is equivalent to x = x // y
• Exponentiation assignment (**=) raises to a power and assigns it, e.g., x **= y is equivalent to x = x ** y

Comparison Operators

• Comparison operators determine the equality or difference between variables or values in logical statements
• Equal (==) tests if two values are equal, e.g., x == y
• Not equal (!=) tests if two values are not equal, e.g., x != y
• Greater than (>) tests if one value is greater than another, e.g., x > y
• Less than (<) tests if one value is less than another, e.g., x y
• Left shift (<<) shifts bits to the left, adding zeros from the right, e.g., 5 << 1
• Right shift (>>) shifts bits to the right, dropping rightmost bits, e.g., 5 >> 1

Identity Operators

• Identity operators compare the identity of objects, checking if they are the same object with the same memory location

• is returns True if both variables are the same object, e.g., x is y

x = ["apple", "banana"]
y = ["apple", "banana"]
z = x
print(x is z)  # True, z is the same object as x
print(x is y)  # False, x and y are different objects, even with the same content

• is not returns True if both variables are not the same object, e.g., x is not y

x = ["apple", "banana"]
y = ["apple", "banana"]
z = x
print(x is not z)  # False, z is the same object as x
print(x is not y)  # True, x and y are different objects

Membership Operators

• Membership operators test if a sequence is present in an object

x = ["apple", "banana"]
print("banana" in x)       # True
print("pineapple" not in x) # True

• in returns True if a sequence with the specified value is present, e.g., "banana" in x
• not in returns True if a sequence with the specified value is not present, e.g., "pineapple" not in x

Operator Precedence

• Parentheses () have the highest precedence and are evaluated first, print((6 + 3) - (6 + 3)) evaluates to 0 because it calculates to 9-9
• Exponentiation ** is next
• Unary plus, unary minus, and bitwise NOT +x,-x,~x
• Multiplication, division, floor division, and modulus *,/,//,%
• Addition and subtraction +,-
• Bitwise left and right shifts >
• Bitwise AND &
• Bitwise XOR ^
• Bitwise OR |
• Comparisons, identity, and membership operators i.e. ==, !=, >, >=, <, <=, is, is not, in, not in
• Logical NOT not
• Logical AND and
• Logical OR or

Python Booleans

• Booleans represent True or False Values
• In programming you often need to know if an expression is True or False
• You can evaluate any expression in Python, and get one of two answers, True or False
• When you compare two values, the expression is evaluated and python returns the boolean answer

Boolean Values and Variables

• The bool() function evaluates a value and returns True or False
• Most values are True
  • Almost any value is evaluated to True if it has some sort of content
  • Any string is True, except empty strings
  • Any number is True, except 0
  • Any list, typle, set, and dictionary are True, exceot empty ones

    bool("abc") #True
    bool(123) #True
    bool(["apple", "cherry", "banana"]) #True