Frozen Dict: Immutable Dictionaries in Python - Why and How?

Unveiling the Enigmatic "Frozen Dict"

Dictionaries in Python provide a versatile way to store data. However, situations may arise where an immutable version of a dictionary is desired. Enter the hypothetical concept of a "frozen dict."

Much like a frozen set is an immutable version of a set, and a tuple is an immutable version of a list, a frozen dict would offer an immutable counterpart to the mutable dictionary. It should retain key-value functionality, offer hashability, and support common operations like iteration, key access, and equality checks.

In the absence of a built-in frozendict type in Python, developers have sought alternative solutions. One approach involves creating a custom wrapper class, as exemplified by the code provided in the answer.

This wrapper class mimics the behavior of a dict, implementing methods for iteration, item retrieval, and hashing. The hash function incorporates all key-value pairs to ensure consistent object comparison.

Using the wrapper, a frozen dict can be created and utilized much like a regular dict:

<code class="python">>>> x = FrozenDict(a=1, b=2)
>>> y = FrozenDict(a=1, b=2)
>>> x is y
False
>>> x == y
True</code>

Objects of this class exhibit both immutability and hashability, allowing for efficient lookup and storage. As demonstrated in the code examples, they can be compared and used as keys in other dictionaries, showcasing their practicality.

While not natively present in Python's core libraries, the concept of a frozen dict can be realized through custom wrapper classes, offering developers a convenient and immutable alternative to mutable dictionaries.

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