Common Python Interview Questions and Answers

Question 1: What is the difference between a list and a tuple in Python? A list is mutable, allowing its elements to be changed, while a tuple is immutable, meaning its elements cannot be modified.

Question 2: What is the difference between an array and a list in Python? Both store data similarly, but an array can only contain elements of a single data type, whereas a list can hold elements of any type.

Question 3: What is the difference between append() and extend() ? append() adds a single new element to the end of a list, occupying one index slot; extend() adds each element of an iterable to the end of the list, extending it with multiple items.

Question 4: What is the difference between == and is ? is checks whether two variables reference the same object, while == compares the values of the objects for equality.

Question 5: Explain shallow copy and deep copy in Python. For immutable objects (e.g., strings, numbers, booleans), shallow and deep copies behave the same, as they share the same reference. For mutable objects (e.g., lists, dictionaries, sets), a shallow copy copies only the top‑level references, while a deep copy recursively copies all nested mutable objects, creating independent memory spaces.

Question 6: Differentiate break , continue , and pass . break exits the loop entirely; continue skips the remaining statements in the current iteration and proceeds to the next loop cycle; pass does nothing and allows the loop to continue executing subsequent statements.

Question 7: What are local and global variables in Python? A global variable is declared outside any function and can be accessed by any function. A local variable is declared inside a function and exists only within that function’s scope.

Question 8: What is the difference between range and xrange ? In Python 2, range returns a list, while xrange returns an xrange object that generates numbers on demand using a generator‑like technique, saving memory for large sequences.

Question 9: What is a decorator in Python? A decorator is a higher‑order function that wraps another function to add extra functionality without modifying the original code; it returns a new function object and is commonly used for logging, caching, authentication, etc.

Question 10: Explain iterators and generators in Python. An iterable object implements __iter__ (or __getitem__ ) and can produce an iterator via iter() . An iterator implements __next__ to retrieve successive items. A generator is a special kind of iterator defined with the yield keyword, providing a concise way to create iterators.