# Datatypes This guide is a quick reference for the fundamental built-in data types in Python. --- ### Numeric Types Used for holding numerical values. * **Integer (`int`)**: Represents positive or negative whole numbers without a decimal point. ```python # An integer user_count = 150 print(f"Value: {user_count}, Type: {type(user_count)}") # Output: Value: 150, Type: ``` * **Float (`float`)**: Represents real numbers with a decimal point. ```python # A floating-point number price = 99.95 print(f"Value: {price}, Type: {type(price)}") # Output: Value: 99.95, Type: ``` * **Complex (`complex`)**: Represents numbers with a real and imaginary part. ```python # A complex number z = 2 + 3j print(f"Value: {z}, Type: {type(z)}") # Output: Value: (2+3j), Type: ``` --- ### Sequence Types Ordered collections of items. You can access items by their index. * **String (`str`)**: An ordered, **immutable** sequence of characters. ```python # A string greeting = "Hello, Python!" print(f"Value: '{greeting}', Type: {type(greeting)}") # Output: Value: 'Hello, Python!', Type: ``` * **List (`list`)**: An ordered, **mutable** (changeable) sequence of items. ```python # A list scores = [88, 92, 77, 99, 85] scores.append(100) # Lists can be modified print(f"Value: {scores}, Type: {type(scores)}") # Output: Value: [88, 92, 77, 99, 85, 100], Type: ``` * **Tuple (`tuple`)**: An ordered, **immutable** (unchangeable) sequence of items. ```python # A tuple coordinates = (10.0, 20.0) # coordinates[0] = 15.0 <-- This would raise a TypeError! print(f"Value: {coordinates}, Type: {type(coordinates)}") # Output: Value: (10.0, 20.0), Type: ``` --- ### Mapping Type An unordered collection of key-value pairs. * **Dictionary (`dict`)**: A **mutable** collection where each item is a pair consisting of a unique key and its associated value. ```python # A dictionary student = { "name": "Alice", "id": 12345, "is_enrolled": True } student['id'] = 54321 # Dictionaries are mutable print(f"Value: {student}, Type: {type(student)}") # Output: Value: {'name': 'Alice', 'id': 54321, 'is_enrolled': True}, Type: ``` --- ### Set Types Unordered collections of unique items. * **Set (`set`)**: A **mutable**, unordered collection of **unique** elements. ```python # A set - duplicates are automatically removed tags = {'python', 'coding', 'dev', 'python'} print(f"Value: {tags}, Type: {type(tags)}") # Output: Value: {'dev', 'python', 'coding'}, Type: (order may vary) ``` --- ### Boolean Type Used for representing truth values. * **Boolean (`bool`)**: Can only have one of two values: `True` or `False`. ```python # A boolean is_active = True has_permission = False print(f"Value: {is_active}, Type: {type(is_active)}") # Output: Value: True, Type: ``` --- ### None Type Represents the absence of a value. * **NoneType (`None`)**: Has only one value: `None`. Often used as a placeholder. ```python # The NoneType winner = None print(f"Value: {winner}, Type: {type(winner)}") # Output: Value: None, Type: ``` ### Quick Summary Table | Category | Datatype | Example | Key Characteristics | | --------------- | --------------- | ----------------------------------- | ------------------------------------ | | **Numeric** | `int` | `42` | Integer numbers | | | `float` | `3.14159` | Floating-point numbers | | **Sequence** | `str` | `"Hello"` | Ordered, Immutable | | | `list` | `[1, "a", 2.0]` | Ordered, **Mutable** | | | `tuple` | `(1, "a", 2.0)` | Ordered, Immutable | | **Mapping** | `dict` | `{"key": "value"}` | Unordered (Ordered in 3.7+), **Mutable** | | **Set** | `set` | `{1, 2, 3}` | Unordered, **Mutable**, Unique items | | **Boolean** | `bool` | `True` or `False` | Truth value | | **None** | `NoneType` | `None` | Represents absence of value |