Learn about Python Conditions

Lesson: Understanding Boolean Variables and Operators in Python – Python Conditions

Objective:

By the end of this lesson, you should understand:

• Boolean values and their use in evaluating expressions.
• The difference between assignment (=) and comparison (==) operators.
• Boolean operators (and, or, not) for constructing complex expressions.
• The use of the in operator for checking membership in an iterable.
• The difference between == and is.
• Code blocks and indentation in Python.

Introduction to Boolean Variables

Boolean variables in Python represent one of two values: True or False. These values are returned when an expression is evaluated.

Examples:

Assignment vs. Comparison

• Assignment (=): Assigns a value to a variable.
• Comparison (==): Compares two values.

Not Equals Operator: The operator != checks if two values are not equal.

Boolean Operators

1. and and or

These are used to build complex Boolean expressions.

Examples:

2. in Operator

Checks membership of an element in an iterable.

Example:

Python Indentation

Python uses indentation instead of brackets to define code blocks. Always use consistent indentation (standard: 4 spaces).

Example:

Empty Objects and Truthy Values

Objects are considered True unless they are empty or explicitly False.

Examples of Empty Objects:

• An empty string: ""
• An empty list: []
• The number zero: 0

The is Operator

is checks if two variables refer to the same object, not just if their values are equal.

Example:

The not Operator

Inverts the result of a Boolean expression.

Examples:

Assignment – Python Conditions

Task: Change the variables so each if statement evaluates to True.

Answer Key – Python Conditions

1. Why number > 15 is True:
   • number = 16, which is greater than 15.
2. Why first_array is True:
   • A non-empty list ([1, 2, 3]) evaluates to True.
3. Why len(second_array) == 2 is True:
   • second_array has 2 elements.
4. Why len(first_array) + len(second_array) == 5 is True:
   • The sum of lengths of [1, 2, 3] and [1, 2] equals 5.
5. Why first_array and first_array[0] == 1 is True:
   • first_array[0] equals 1.
6. Why not second_number is True:
   • second_number = 0, which is equivalent to False. not False is True.

Assignment Questions

1. Write a program to check if a number is positive, negative, or zero.
2. Modify the given code so it prints additional messages based on the value of number.
3. Write a function that takes a list and checks if it contains a specific value using the in operator.

Overview and Wrap-Up

This lesson explored the fundamentals of Boolean variables and operators in Python. You learned how to use Boolean values (True, False) to evaluate conditions and build logical expressions. Key concepts included the distinction between assignment (=) and comparison (==) operators, and how operators like and, or, and not allow for complex logic. The in operator was introduced for checking membership in lists or other iterables, while the is operator highlighted how to compare object identities.

Python’s reliance on indentation to define code blocks and the truthiness of objects like lists or strings were also discussed. Finally, you saw examples of practical applications for these concepts through exercises.

Key Takeaway

Boolean logic is at the core of programming decisions and condition evaluations. Mastering these basics will help you write more effective, logical, and error-free Python code.