What are the differences between type() and isinstance() in Python?

The type() and isinstance() functions in Python are used for type checking, but they serve different purposes and behave differently. Here’s a breakdown of their key differences:

1. Inheritance Handling

type():
Checks the exact type of an object. It does not consider inheritance.
Example:

  class Animal: pass
  class Dog(Animal): pass

  d = Dog()
  print(type(d) is Dog)    # True
  print(type(d) is Animal) # False (exact match only)

isinstance():
Checks if an object is an instance of a class or any of its subclasses.
Example:

  print(isinstance(d, Dog))    # True
  print(isinstance(d, Animal)) # True (inheritance-aware)

2. Boolean vs. Integer Types

bool is a subclass of int:
isinstance(True, int) returns True, but type(True) is int returns False.
Example:

  print(isinstance(True, int))  # True (inheritance)
  print(type(True) is int)      # False (exact type is bool)

3. Multiple Type Checks

isinstance() allows checking against multiple types using a tuple:

  value = 42
  print(isinstance(value, (int, float)))  # True (checks int or float)

type() requires explicit checks:

  print(type(value) in (int, float))      # True

4. Performance

type() is slightly faster for exact checks since it doesn’t traverse inheritance hierarchies.
isinstance() is more flexible but incurs overhead for checking parent classes.

5. Use Cases

Use type() when:
You need an exact type match (e.g., distinguishing bool from int).
You explicitly want to exclude subclasses.
Use isinstance() when:
Checking for any class in an inheritance hierarchy.
Writing flexible code that accommodates subclasses.
Handling multiple types (e.g., (int, float)).

Example Summary

class Parent: pass
class Child(Parent): pass

obj = Child()

# type() behavior
print(type(obj) is Child)   # True
print(type(obj) is Parent)  # False

# isinstance() behavior
print(isinstance(obj, Child))   # True
print(isinstance(obj, Parent))  # True (inheritance-aware)

Key Takeaways

type(): Exact type checks, no inheritance.
isinstance(): Inheritance-aware, supports multiple types.
Prefer isinstance() for most use cases to ensure compatibility with subclasses.
Use type() sparingly (e.g., distinguishing bool from int).

Choose the method that aligns with your need for strict or flexible type checking!