Python Interview Questions for Freshers

A list is mutable and a tuple is immutable. Tuples are slightly faster, can be used as dictionary keys if their items are hashable, and suit fixed records. Lists suit collections that change.

It is a hash table that maps keys to values, with average constant-time lookup. Keys must be hashable, and since Python 3.7 a dictionary keeps insertion order.

*args collects extra positional arguments into a tuple and **kwargs collects extra keyword arguments into a dictionary. They let a function accept any number of arguments.

A function that takes a function and returns a new one that adds behaviour, such as logging or timing, without changing the original code. It is written with the @ syntax.

== checks whether two values are equal, while is checks whether they are the same object in memory. Use is for None checks, and == for comparing values.

A short way to build a list from another sequence, like [x * x for x in numbers if x > 0]. It is usually clearer and faster than a loop that appends.

Mainly by reference counting, where an object is freed when nothing refers to it, plus a garbage collector that finds reference cycles. Python also pools small objects.

A shallow copy copies the outer object but shares the inner objects, so changing a nested item shows in both. A deep copy copies everything inside too. Use copy.deepcopy for nested data.

Functions that use yield to produce values one at a time instead of building a whole list. They save memory and are good for large or endless streams of data.

The Global Interpreter Lock in CPython lets only one thread run Python bytecode at a time. Threads still help with waiting on input and output, but for heavy computation use multiprocessing.

The default value is created once when the function is defined, so a default list is shared between calls. Use None as the default and create the list inside the function.