Operators

1. Arithmetic Operators

An arithmetic operation in Python involves applying mathematical operators to values (operands). Here’s the anatomy of an operation:

>>> 10 + 5
15

Arithmetic Operator Symbols and Their Operations

These operators are binary operators, meaning they operate on two operands. Let’s explore each operator:

>>> 10 + 5   # Addition
15
>>> 10 - 5   # Subtraction
5
>>> 10 * 5   # Multiplication
50
>>> 10 / 5   # Division
2.0
>>> 10 // 5  # Floor Division
2
>>> 10 % 5   # Modulus (Remainder)
0
>>> 10 ** 5  # Exponentiation (Power)
100000

Explanation of Floor Division, Modulus, and Exponentiation

• // Floor Division: Divides two numbers and returns the integer quotient, discarding any remainder.

  >>> 8 // 3
  2  # The quotient is 2, remainder is discarded.

• % Modulus: Returns the remainder of a division.

  >>> 10 % 3
  1  # The remainder is 1.

• **** Exponentiation**: Raises one number to the power of another.

  >>> 2 ** 3
  8  # 2 raised to the power of 3.

Division vs Floor Division

The / operator performs division and returns the exact result (as a float), while // returns only the integer part (quotient).

>>> 5 / 2
2.5  # Standard division
>>> 5 // 2
2    # Floor division

Unary Operators: + and -

Unlike the binary operators mentioned above, the + and - operators can also act as unary operators (operating on one operand). They indicate positive or negative numbers.

>>> -2    # Unary minus
-2
>>> +2    # Unary plus
2

Variable Usage in Arithmetic Operations

While we’ve used literals so far, arithmetic operations can also be applied to variables:

>>> x = 1
>>> y = x * 5
>>> print(x, y)
1 5

2. Relational Operators

Relational operators are used to compare two values. The result is a boolean (True or False).

Relational Operator Symbols and Their Operations

These operators are also binary operators. Examples:

>>> 10 > 5
True
>>> 10 < 5
False
>>> 10 >= 5
True
>>> 10 <= 5
False
>>> 10 == 5
False
>>> 10 != 5
True

Relational operators are also known as comparison operators, as they compare two operands and return a boolean value. You can assign the result of a comparison to a variable:

>>> x = 10
>>> y = 15
>>> z = y > x
>>> print(z)
True

Note: The == operator checks for equality and should not be confused with = which is used for assignment.

3. Logical Operators

Logical operators are used to combine multiple boolean expressions. They operate on boolean values and return a boolean result.

Logical Operator Symbols and Their Operations

• and and or are binary operators.
• not is a unary operator.

Examples

>>> True and False
False

>>> True or False
True

>>> x = False
>>> y = not x
>>> print(y)
True

The not operator inverts the boolean value (True becomes False, and vice versa). Parentheses can be used but are optional:

>>> x = True
>>> not x
False

>>> x = False
>>> not(x)
True

4. Code Convention

Consider the following lines of code:

>>> print(1 + 2)
3
>>> print(1+2)
3

Both lines produce the same output. In this course, we will follow the first convention—always adding spaces around operators for readability:

>>> x = 2  # We will follow this.
>>> x=2    # We will NOT follow this.

Both are syntactically correct, but adding spaces makes the code more readable.

5. Expressions

An expression in Python is a combination of literals, variables, and operators that evaluates to a value. Here are a few examples:

1 + 4 / 4 ** 0
x / y + z * 2.0
3 > 4 and 1 < 10
not True and False

Each expression evaluates to a value, which has a specific type. For example:

• The first two expressions result in a float.
• The next two result in a bool.

Arithmetic Expressions

An arithmetic expression evaluates to a numeric value (int or float). Here’s an example:

>>> 1 + 2
3
>>> type(1 + 2)
<class 'int'>

If one operand is a float, the result will also be a float:

>>> 1.0 + 2
3.0
>>> type(1.0 + 2)
<class 'float'>

Boolean Expressions

A boolean expression results in a bool value (True or False), typically through the use of relational or logical operators:

>>> 2 > 1
True
>>> type(2 > 1)
<class 'bool'>

Similarly, logical operators produce boolean results:

>>> True and False
False
>>> type(True and False)
<class 'bool'>

Truth Tables for Logical Operators

A truth table lists all possible outcomes for a logical expression. For example, the truth table for or is:

By understanding these operators and how they work in expressions, you’ll have a strong foundation to write more complex Python programs.