Skip to main content

Text, Boolean, and None — Representing Meaning Beyond Numbers

What You'll Learn​

  • Text data (strings)
  • True/False decisions (booleans)
  • Truthy and falsy values
  • Representing "nothing" (None)
  • Why strings can't change

You've mastered numbers in the previous lesson. But programming isn't just about math—it's about representing all kinds of information. Consider these everyday examples:

  • Text: "Hello", "alice@example.com", "Room 404"
  • True or False: Light switch ON/OFF, Fridge EMPTY/FULL, Answer YES/NO
  • Nothing: No milk available, no response received, no data found

These everyday examples represent three types of data that Python needs:

  • Text (str): "Hello", "alice@example.com", "Room 404"
  • True/False (bool): Switch is ON, Fridge is EMPTY, Question is YES
  • Nothing (None): No milk, no response, no data

This lesson teaches you Python's three most expressive types: str (strings), bool (booleans), and None (absence). Together, they let you represent the richness of real-world meaning.

Concept 1: What Is a String (str)?​

A string is a sequence of characters—letters, numbers, symbols, spaces, and punctuation all in order. It's how Python stores text.

Examples of Strings​

Loading Python environment...

Key characteristics:

  • A sequence: Made of individual characters in a string together
  • Immutable: Once created, you can't change individual characters (you create a new string instead)
  • Ordered: Position matters ("bat" ≠ "tab")
  • Can be empty: "" is a valid string with zero characters

Why Use Strings?​

Strings represent any text data:

  • Names, emails, usernames
  • Messages, labels, descriptions
  • File paths, URLs, IDs
  • Anything that isn't a number or True/False

When you need to store, display, or process words or text, use str.

Quote Variations: Three Ways to Write Strings​

Python gives you three ways to write strings, all equally valid. The choice depends on your content:

Single Quotes: 'hello'​

Loading Python environment...

Use when your string contains double quotes:

Loading Python environment...

Double Quotes: "hello"​

Loading Python environment...

Use when your string contains single quotes (apostrophes):

Loading Python environment...

Triple Quotes: '''...''' or """..."""​

Loading Python environment...

Use for multi-line strings (text spanning multiple lines). Triple quotes preserve line breaks.

Key insight: All three quote types create strings. Pick whichever keeps your code readable:

Loading Python environment...

String Immutability: You Can't Change Individual Characters​

Immutable means unchangeable. Once a string is created, you cannot modify its individual characters.

Loading Python environment...

If you want "Blice", you must create a new string:

Loading Python environment...

Why immutability matters: It prevents accidental changes to data and makes strings predictable. In AI-native development, immutability is a safety guarantee—your AI collaborator knows strings won't be modified unexpectedly.

Concept 2: What Is a Boolean (bool)?​

A boolean is a data type with exactly two possible values: True or False. It's for yes/no, on/off, pass/fail decisions.

Examples of Booleans​

Loading Python environment...

Key Characteristics​

  • Only two values: True or False (nothing else)
  • Capitalization matters: True and False (uppercase). Python will reject true or false
  • Represent logic: Answer yes/no questions, control program flow

Why Use Booleans?​

Booleans answer yes/no questions:

  • Is the user logged in? True or False
  • Has the user paid? True or False
  • Is the product in stock? True or False
  • Is the password correct? True or False

When to choose bool: Any time you need to represent a binary (two-choice) state.

Code Example: Boolean Variables​

Loading Python environment...

Concept 3: Truthy and Falsy Values​

Here's a powerful concept that prepares you for conditional statements (Chapter 22):

In Python, almost EVERY value can be treated as True or False. Some values are naturally "falsy" (act like False), and everything else is "truthy" (acts like True).

Understanding Falsy Values​

These values are considered False:

ValueTypeMeaning
FalseboolLiterally the boolean False
0intZero (no count)
0.0floatZero (no measurement)
""strEmpty string (no text)
[]listEmpty list (no items)
{}dictEmpty dict (no key-value pairs)
NoneNoneTypeAbsence of value

Understanding Truthy Values​

Everything else is True:

ValueTypeMeaning
TrueboolLiterally the boolean True
1, -5, 99intAny non-zero number
0.1, -3.14floatAny non-zero decimal
"hello"strAny non-empty string
[1, 2, 3]listAny non-empty list
{"a": 1}dictAny non-empty dict

Checking Truthiness with bool()​

The bool() function converts any value to True or False:

Loading Python environment...

Code Demonstration: Truthy/Falsy in Context​

Loading Python environment...

Why Truthy/Falsy Matters​

Understanding truthy/falsy values prepares you for Chapter 22, where you'll learn to write conditional logic like:

  • Checking if a username is not empty (truthy check)
  • Verifying if age meets requirements (comparison)
  • Testing if a user has premium status (boolean check)

AI Prompt Used for this section: ""Create a Python script that demonstrates truthy and falsy values. Show examples of False-evaluating values (0, '', [], {}, None) and truthy values (1, 'hello', [1,2], {'a': 1}). Use bool() to convert each to True/False.""

Generated Code:

Loading Python environment...

Validation Steps:

  • ✓ Ran on Windows, Mac, and Linux—works across platforms
  • ✓ Correctly identifies all falsy values evaluate to False
  • ✓ Correctly identifies all truthy values evaluate to True
  • ✓ Output format clear and easy to understand
  • ✓ No control flow statements (loops/conditionals taught in Chapter 22)

Concept 4: What Is None?​

None is a special value representing absence—"nothing," "no data," "no result."

None Is NOT Zero or Empty​

Many beginners confuse None with 0 or "". They're completely different:

Loading Python environment...

The semantic difference:

  • 0 = "The count is zero" (a count that exists)
  • "" = "The message is empty" (a string that exists but has no text)
  • None = "There is no value at all" (nothing exists)

None as a Singleton​

There is exactly ONE None object in the entire Python program:

Loading Python environment...

This singleton property means checking if x is None: is the correct Python idiom (not if x == None:).

Why Use None?​

None represents missing or absent data:

  • Function has no result: return None
  • Optional parameter not provided: name: str | None = None
  • Data field is missing: phone: str | None = None
  • Placeholder for data you'll fill later: result: int | None = None

Examples of None​

Loading Python environment...

Key syntax: Use str | None (read as "string or None") to indicate a value that could be text OR nothing.

Practice Exercise 1: Identify Truthy/Falsy Values​

For each value below, determine whether it's truthy or falsy. Write your answer as T (truthy) or F (falsy):

Loading Python environment...

Answers (check yourself after completing):

1. F  2. F  3. F  4. T  5. F  6. T  7. F  8. T  9. F  10. T
11. T  12. T  13. T  14. F  15. F

Practice Exercise 2: Choose the Right Type (str, bool, or None)​

For each scenario, decide whether you'd use str, bool, or None:

Loading Python environment...

Your answers:

Loading Python environment...

Practice Exercise 3: Fix the String Quote Error​

The code below has quote-related issues. Fix them:

Loading Python environment...

Your corrections:

Loading Python environment...

Common Pitfalls​

Pitfall 1: Forgetting Quote Matching​

Loading Python environment...

Pitfall 2: Confusing True/False Capitalization​

Loading Python environment...

Pitfall 3: Treating None Like Zero or Empty String​

Loading Python environment...

Pitfall 4: Trying to Modify Strings​

Loading Python environment...

Pitfall 5: Forgetting Triple Quotes for Multi-line​

Loading Python environment...

Why This Matters: Semantic Clarity​

Here's the big picture: Type hints communicate semantic meaning, not just syntax.

When you write:

Loading Python environment...

You're telling your AI collaborator (and future you):

  1. user_name is text representing a person's name
  2. is_premium_member is a yes/no decision about membership status
  3. phone_number could be a phone (text) or nothing (absent data)

This semantic clarity enables your AI collaborator to:

  • Suggest string operations (uppercase, split, validate email)
  • Understand boolean logic for decision-making
  • Handle optional fields correctly (default values, validation)

In AI-native development, clear type specifications are how you communicate intent—not just to Python, but to your AI partner.

🎓 Expert Insight​

At scale (1000+ variables), type hints with semantic naming prevent entire classes of bugs. When you see confirmed: bool, you immediately know it's a yes/no decision. When you see phone: str | None, you know to handle the "no phone" case. This clarity becomes AI-readable specifications. Professional codebases (Stripe, Google, Meta) rely on type hints as executable documentation.

Try With AI​

Ready to master truthy/falsy evaluation and None semantics?

🔍 Explore Truthy/Falsy Patterns:

"Test these 10 values with bool() and tell me which are truthy and falsy: '', 'hello', 0, 42, [], [1,2], None, False, True, '0'. Explain the pattern you observe. Why is '0' (string) truthy but 0 (int) falsy? What's the rule for empty vs. non-empty values?"

🎯 Practice Boolean Validation:

"Create a user registration validator that checks: (1) username is not empty, (2) age is not None and not zero, (3) email contains '@'. Use truthy/falsy checking instead of explicit comparisons like == ''. Show me the code with type hints and explain why if not username: is better than if username == '':"

🧪 Test None vs. Empty Semantics:

"Explain the difference between missing_data = None, zero_value = 0, and empty_text = ''. For optional user input (like middle name), which should I use? Create code showing why if value is None: is correct but if value == 0: would be wrong. Include a real bug this causes."

🚀 Apply to Your Forms:

"I'm building a form for [describe your application]. Help me identify which fields are required (str), optional (str | None), and boolean decisions (bool). For each field, show me the correct validation logic using truthy/falsy evaluation and None checking."