Shyama Sankar Vellore: Python Dictionaries: Cheat Sheet

A cheat sheet for dictionaries in Python.
What is the dictionary datatype in Python? How to use it? Some key points and several examples of its usage.

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Key points

• Dictionary is a commonly used collection datatype in Python; the others being lists, sets, and tuples.
• A dictionary is essentially a set of key-value pairs, where, the keys should be unique and immutable.
• A dictionary is mutable, i.e., it can be modified in place after it is created. We can add, remove or update items in a dictionary.
• Keys could be of any immutable data type, i.e., string, number, or even a tuple of immutable objects. [Note: Immutable objects are objects which cannot be modified in place once they are created. Python's built-in immutable objects include numbers, strings, and tuples].
• Dictionaries are indexed using their keys.
• Dictionaries are created using a pair of curly braces, i.e., {}, or by using the dict() constructor.
• We can create and initialize a dictionary with items by adding a comma-separated list of key-value pairs within the curly braces. The 'dict' constructor also takes an optional iterable, mapping, or keyword arguments as input.
• For examples on how to create a dictionary, add elements, update elements, remove elements, etc, see the cheat sheet.

Cheat sheet

Useful resources and references

• Python documentation for dictionaries
• Python documentation for 'dict' constructor

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