Python: Mutable vs. Immutable
Everything in Python is an object . You have to understand that Python represents all its data as objects. An object’s mutability is determined by its type. Some of these objects like lists and dictionaries are mutable , meaning you can change their content without changing their identity. Other objects like integers, floats, strings and tuples are objects that can not be changed.
List is mutable
Tuple is immutable
If you want to write most efficient code, you should be the knowing difference between mutable and immutable in python. Concatenating string in loops wastes lots of memory , because strings are immutable, concatenating two strings together actually creates a third string which is the combination of the previous two. If you are iterating a lot and building a large string, you will waste a lot of memory creating and throwing away objects. Use list compression join technique.
Python handles mutable and immutable objects differently. Immutable are quicker to access than mutable objects. Also, immutable objects are fundamentally expensive to "change", because doing so involves creating a copy. Changing mutable objects is cheap.
- Python Interview Questions FAQ - 1
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