Python Dictionaries

Flashcards covering key concepts of Python dictionaries, including creation, manipulation, and methods.

Dictionary

An object that stores a collection of data in key-value pairs. Keys must be immutable objects.

Retrieving a Value

Use dictionary[key]. Raises KeyError if key is not found. Use 'in' and 'not in' to check for key existence.

Adding Elements

Dictionaries are mutable. Add key-value pairs using dictionary[key] = value. Overwrites if key exists.

Deleting Elements

Use del dictionary[key]. Raises KeyError if key is not found.

len() function

Used to obtain the number of elements in a dictionary.

Key Constraints

Keys must be immutable objects, but values can be of any type.

Creating Empty Dictionary

Use {} or dict(). Add elements as program executes.

Iterating with For Loop

Use for key in dictionary: to iterate over keys.

clear() method

Deletes all elements in a dictionary, making it empty.

get() method

Returns value associated with specified key. Returns default (or None) if key is not found, avoiding KeyError.

items() method

Returns all keys and their associated values as a dictionary view (sequence of tuples).

keys() method

Returns all the dictionary's keys as a sequence.

values() method

Returns all the dictionary's values as a sequence.

pop() method

Returns value associated with specified key and removes the key-value pair. Optional default value if key not found.

popitem() method

Returns and removes the last added key-value pair as a tuple.