🐍INTROSPECTION & UTILITIES

Python provides built-in functions to examine objects, check properties, and explore your code interactively. This is called introspection.

What is Introspection?

Introspection is the ability of a program to examine the type or properties of objects at runtime. Python provides several built-in functions for introspection.

Common Built-in Introspection & Utility Functions

# dir(): lists attributes and methods of an object
print(dir(list))

# type(): returns type of object
x = 10
print(type(x))

# isinstance(): checks if object is of a certain type
print(isinstance(x, int))   # True

# callable(): checks if object can be called (like functions)
def greet():
    print("Hello!")
print(callable(greet))      # True
print(callable(x))          # False

# id(): returns unique ID of object in memory
print(id(x))

# help(): shows documentation of object or function
help(len)

Common Mistakes

• Calling dir() on an undefined variable → NameError
• Forgetting parentheses for callable() → returns object info, not evaluation
• Using help() incorrectly without an object → opens interactive help unexpectedly
• Confusing type() and isinstance() when checking inheritance

💡 Try It Yourself

1. Use dir() on a string and a list.
2. Check if a variable is an integer using isinstance().
3. Check if a function is callable using callable().
4. Print the unique ID of two different variables using id().
5. Use help() on the sum function to see its documentation.

Next Steps

After mastering introspection and utilities, the final subtopic in built-in functions will cover Common Mistakes with Built-in Functions so you can avoid pitfalls.

➡️ Next: Common Mistakes with Built-in Functions

⬅️ Back to Main Page

🖥️ Practice in Browser