How to properly subclass dict and override __getitem__ & __setitem__ in python

How to properly subclass dict and override __getitem__ & __setitem__ in python

To subclass the dict class and override the __getitem__ and __setitem__ methods in Python, you can create a custom dictionary class that inherits from dict and then provide your own implementations for these methods. Here's an example:

class CustomDict(dict): def __getitem__(self, key): # Your custom __getitem__ implementation here if key not in self: return "Key not found" return super().__getitem__(key) def __setitem__(self, key, value): # Your custom __setitem__ implementation here # For example, you can restrict setting certain keys or modify values super().__setitem__(key, value) # Usage my_dict = CustomDict() # Setting values my_dict['a'] = 1 my_dict['b'] = 2 # Getting values print(my_dict['a']) # Output: 1 print(my_dict['c']) # Output: Key not found

In this example:

  1. We define a custom dictionary class called CustomDict that inherits from the built-in dict class.

  2. We override the __getitem__ method to provide our custom behavior when accessing items using square brackets (e.g., my_dict['a']). In this example, we check if the key exists in the dictionary and return a custom message if it does not.

  3. We override the __setitem__ method to provide our custom behavior when setting items using square brackets (e.g., my_dict['a'] = 1). You can add custom logic here to modify or restrict the setting of certain keys.

  4. We create an instance of our CustomDict class and use it like a regular dictionary.

By subclassing dict and overriding these methods, you can customize the behavior of your dictionary class to suit your specific needs.

Examples

  1. "Python subclass dict override getitem setitem"

    • Description: This query focuses on subclassing the built-in dict class in Python and overriding the __getitem__ and __setitem__ methods to customize their behavior.
    class CustomDict(dict): def __getitem__(self, key): # Custom implementation for __getitem__ pass def __setitem__(self, key, value): # Custom implementation for __setitem__ pass

  2. "Python dict subclass getitem example"

    • Description: Users may seek examples of how to override the __getitem__ method in a subclass of dict to customize key access behavior.
    class CustomDict(dict): def __getitem__(self, key): if key == 'special_key': return 'special_value' else: return super().__getitem__(key)

  3. "Python dict subclass setitem example"

    • Description: This query focuses on examples of overriding the __setitem__ method in a subclass of dict to customize value assignment behavior.
    class CustomDict(dict): def __setitem__(self, key, value): if isinstance(value, str): value = value.upper() # Convert value to uppercase if it's a string super().__setitem__(key, value)

  4. "Python dict subclass getitem setitem example"

    • Description: Users may look for combined examples demonstrating both __getitem__ and __setitem__ overrides in a subclass of dict.
    class CustomDict(dict): def __getitem__(self, key): if key == 'special_key': return 'special_value' else: return super().__getitem__(key) def __setitem__(self, key, value): if isinstance(value, str): value = value.upper() # Convert value to uppercase if it's a string super().__setitem__(key, value)

  5. "Python dict subclass custom getitem"

    • Description: Users may want to know how to customize the behavior of the __getitem__ method in a subclass of dict for specific key accesses.
    class CustomDict(dict): def __getitem__(self, key): # Custom logic based on key pass

  6. "Python dict subclass custom setitem"

    • Description: This query relates to customizing the behavior of the __setitem__ method in a subclass of dict for specific value assignments.
    class CustomDict(dict): def __setitem__(self, key, value): # Custom logic based on value or key pass

  7. "Python dict subclass override getitem"

    • Description: Users may want to understand how to override the default behavior of the __getitem__ method in a subclass of dict.
    class CustomDict(dict): def __getitem__(self, key): # Custom implementation for __getitem__ pass

  8. "Python dict subclass override setitem"

    • Description: This query relates to overriding the default behavior of the __setitem__ method in a subclass of dict.
    class CustomDict(dict): def __setitem__(self, key, value): # Custom implementation for __setitem__ pass

  9. "Python dict subclass getitem setitem example code"

    • Description: Users may specifically seek example code demonstrating how to override both __getitem__ and __setitem__ methods in a subclass of dict.
    class CustomDict(dict): def __getitem__(self, key): # Custom implementation for __getitem__ pass def __setitem__(self, key, value): # Custom implementation for __setitem__ pass

  10. "Python dict subclass override getitem setitem"

    • Description: This query focuses on overriding both __getitem__ and __setitem__ methods in a subclass of dict to provide custom functionality.
    class CustomDict(dict): def __getitem__(self, key): # Custom implementation for __getitem__ pass def __setitem__(self, key, value): # Custom implementation for __setitem__ pass

More Tags

d3.js ng-packagr hamcrest linefeed partial nscala-time lamp edid asp.net-apicontroller aio-write

More Python Questions

More Dog Calculators

More Cat Calculators

More Auto Calculators

More Statistics Calculators