Real interview questions from top companies for Python. Includes theoretical concepts and coding problems.
What are the basic data types in Python?
The basic data types in Python are integers, floats, strings, lists, dictionaries, sets, and tuples.
What is the difference between static typing and dynamic typing?
Static typing means that the data type of a variable is known at compile time, whereas dynamic typing means that the data type of a variable is determined at runtime. Python is dynamically typed.
What is object-oriented programming in Python?
Object-oriented programming in Python is a programming paradigm that revolves around the concept of objects and classes. It includes features such as inheritance, polymorphism, encapsulation, and abstraction.
What is the purpose of the 'self' parameter in Python classes?
The 'self' parameter in Python classes is a reference to the current instance of the class and is used to access variables and methods from the class.
What is the difference between a list and a tuple in Python?
A list in Python is a mutable collection of items, whereas a tuple is an immutable collection of items. Lists are defined using square brackets [], whereas tuples are defined using parentheses ().
What is the purpose of the 'try-except' block in Python?
The 'try-except' block in Python is used for exception handling. It allows you to execute a block of code and catch any exceptions that may occur, preventing the program from crashing.
What is the difference between the 'is' and '==' operators in Python?
The 'is' operator in Python checks if two variables refer to the same object in memory, whereas the '==' operator checks if the values of two variables are equal.
What is the purpose of the 'with' statement in Python?
The 'with' statement in Python is used for exception handling and resource management. It ensures that resources such as files are properly closed after use, regardless of whether an exception occurs or not.
What is the difference between a generator and an iterator in Python?
A generator in Python is a special type of function that can be used to generate a sequence of results, whereas an iterator is an object that allows you to iterate over a sequence of results. Generators are defined using the 'yield' keyword.
What is the purpose of the 'lambda' function in Python?
The 'lambda' function in Python is a small anonymous function that can be defined inline within a larger expression. It is often used for simple operations such as sorting or filtering.
What is the difference between the 'map', 'filter', and 'reduce' functions in Python?
The 'map' function in Python applies a given function to each item of an iterable, the 'filter' function filters items from an iterable based on a given condition, and the 'reduce' function applies a given function to the first two items of an iterable, then to the result and the next item, and so on.
What is the purpose of the 'enumerate' function in Python?
The 'enumerate' function in Python returns a tuple containing a count (from the start which defaults to 0) and the values obtained from iterating over the sequence ('iterable').
What is the difference between the 'zip' and 'unzip' functions in Python?
The 'zip' function in Python takes iterables, aggregates them in a tuple, and returns it. The 'unzip' function is not a built-in function in Python, but it can be achieved using the '*' operator to unpack the zipped list.
What is the purpose of the 'all' and 'any' functions in Python?
The 'all' function in Python returns True if all elements of an iterable are true, whereas the 'any' function returns True if at least one element of an iterable is true.
What is the difference between the 'break' and 'continue' statements in Python?
The 'break' statement in Python terminates the loop entirely, whereas the 'continue' statement skips the rest of the code inside a loop for the current iteration only.
What is the purpose of the 'pass' statement in Python?
The 'pass' statement in Python is a null operation -- when it is executed, nothing happens. It is useful as a placeholder when a statement is required syntactically but no execution of code is necessary.
What is the difference between the 'del' and 'remove' methods in Python lists?
The 'del' statement in Python can be used to remove an item from a list by its index, whereas the 'remove' method removes the first occurrence of a specified value.
What is the purpose of the 'copy' method in Python lists?
The 'copy' method in Python returns a copy of the specified list.
What is the difference between shallow and deep copying in Python?
Shallow copying in Python constructs a new compound object and then (to the extent possible) inserts references into it to the objects found in the original. Deep copying in Python constructs a new compound object and then, recursively, inserts copies into it of the objects found in the original.
Write a Python function to find the maximum of two numbers.
deffind_max(a, b): return a if a > b else b
Write a Python function to find the first duplicate in an array of integers.
deffind_duplicate(arr): seen = set();
for num in arr: if num in seen: return num;
seen.add(num);
returnNone
Write a Python function to find the middle element of a linked list.
classNode: def__init__(self, data): self.data = data;
self.next = None;
classLinkedList: def__init__(self): self.head = None;
deffind_middle(self): slow = self.head;
fast = self.head;
while fast and fast.next: slow = slow.next;
fast = fast.next.next;
return slow.data
Write a Python function to find the maximum subarray sum.
defmax_subarray_sum(arr): max_sum = float('-inf');
current_sum = 0;
for num in arr: current_sum = max(num, current_sum + num);
max_sum = max(max_sum, current_sum);
return max_sum
Write a Python function to find the first non-repeating character in a string.
deffind_first_non_repeating_char(s): char_count = {
}
;
for char in s: if char in char_count: char_count[char] += 1;
else: char_count[char] = 1;
for char in s: if char_count[char] == 1: return char;
returnNone
Write a Python function to find the minimum window substring that contains all characters of another string.
from collections import Counter;
defmin_window(s, t): t_count = Counter(t);
required = len(t_count);
left = 0;
min_len = float('inf');
min_window = None;
formed = 0;
window_counts = {
}
;
for right inrange(len(s)): character = s[right];
window_counts[character] = window_counts.get(character, 0) + 1;
if character in t_count and window_counts[character] == t_count[character]: formed += 1;
while left <= right and formed == required: character = s[left];
if right - left + 1 < min_len: min_len = right - left + 1;
min_window = s[left:right+1];
window_counts[character] -= 1;
if character in t_count and window_counts[character] < t_count[character]: formed -= 1;
left += 1;
return min_window
Write a Python function to find the maximum sum of a subarray of size k.
