What are Python's core data types and how do they behave?

A variable is a name bound to an object, not a typed storage location. Reassigning the name rebinds it to another object, which is why one name can refer to an int and later to a string. Every object carries its type, identity and value.

values = [42, 3.14, True, None, "text", b"bytes", (1, 2), [1, 2], {"a": 1}, {1, 2}]

for value in values:
    print(type(value).__name__, value)

print(isinstance(True, int))  # True
print(type(True) is int)      # False

Grouping the built-ins

• Numeric: int, float, complex, bool, Decimal, Fraction
• Text and binary: str, bytes, bytearray, memoryview
• Sequences: list, tuple, range, str
• Mappings and sets: dict, set, frozenset
• Callables and modules: functions, methods, classes, modules

Immutable objects such as int, str and tuple cannot change after creation, so they are safe to share and can be hashable. Mutable objects such as list, dict and set can change in place, which means two names can observe the same mutation.