Data Science Interview Questions

Python is a high-level, interpreted, and general-purpose programming language known for its simplicity, readability, and versatility. Created by Guido van Rossum in the late 1980s, Python has gained widespread popularity and become a leading choice for developers across various domains. It's a versatile, user-friendly programming language with a clear and readable syntax. Its extensive standard library, platform independence, and large community support make it an attractive choice for developers across diverse domains. Whether for web development, data analysis, artificial intelligence, or any other field, Python's ease of use and robust ecosystem make it a powerful and effective language for various applications.
Key characteristics of Python include its clear and concise syntax, which emphasizes code readability through indentation. This feature makes it easy for beginners to learn and for teams to collaborate effectively on projects. Python's interpreted nature means it does not require a separate compilation step, enabling rapid prototyping and development, which contributes to its popularity for scripting tasks.
One of the primary benefits of using Python is its extensive standard library. The standard library contains numerous modules and packages that facilitate various functionalities, such as working with files, networking, data manipulation, and more. This wealth of pre-built tools saves time and effort, allowing developers to focus on solving specific problems rather than reinventing the wheel.
Another major advantage of Python is its platform independence. Python code can run on different operating systems without modification, which streamlines cross-platform development and deployment. Furthermore, Python's large community actively develops third-party libraries, providing solutions for various domains like web development, data analysis, artificial intelligence, and scientific computing.
Python's versatility also extends to web development, thanks to frameworks such as Django and Flask. Django is a robust, high-level web framework that facilitates rapid development by following the "batteries-included" philosophy. On the other hand, Flask is a lightweight and flexible micro-framework that allows developers to assemble components according to their needs.
Data analysis and scientific computing have thrived with Python, primarily due to libraries like NumPy, pandas, and SciPy. NumPy provides powerful array operations, making it ideal for scientific computations. pandas, built on top of NumPy, offers data structures and tools for data manipulation and analysis. SciPy complements NumPy by providing a collection of algorithms for various scientific and engineering tasks.
Python's influence in the realm of artificial intelligence and machine learning is significant. Libraries such as TensorFlow and PyTorch have revolutionized the field by offering efficient and scalable solutions for building neural networks and conducting large-scale machine learning tasks. The simplicity of Python also makes it an attractive choice for prototyping and experimenting with machine learning models.
The language's strong community support further enhances its appeal. Python developers actively engage in open-source projects, share knowledge, and contribute to enhancing the language's ecosystem. This community-driven approach fosters a positive learning environment and ensures Python continues to evolve and adapt to new challenges.

The main difference between the tuples and lists is that the tuples are immutable objects and lists are mutable. So, tuples cannot be modified while the lists can be modified. Tuples are more memory efficient than the lists and hence are typically faster

Starting with Python 3.7, dictionary is insertion-ordered. So, dict.fromkeys(mylist) will remove the duplicates from a list preserving the original order of the list.

items = [1, 2, 0, 1, 3, 2]
items_new = list(dict.fromkeys(items))
items_new

[1, 2, 0, 3]
To remove the duplicates from a list and the original order of the list need not be preserved, assigning the list to a set and then converting it back to list will remove all the duplicates from the list (sets will not necessarily maintain the order of a list)

items = [1, 2, 0, 1, 3, 2]
items_new = list(set(items))
items_new

[0, 1, 2, 3]

A module is a Python file that’s intended to be imported into scripts or other modules. It can contains functions, classes, and global variables.
A package is a collection of modules that are grouped together inside a folder to provide consistent functionality. Packages can be imported just like modules. They usually have a __init__.py file in them that tells the Python interpreter to process them as such.
A library is a collection of packages.

The difference between shallow and deep copying is only relevant for compound objects (objects that contain other objects, like lists or class instances)
Shallow copying duplicates as little as possible. A shallow copy constructs a new compound object and then (to the extent possible) inserts references into it to the objects found in the original.
Deep copying replicates the original at a different memory location, so the copy is totally independent with no connection to the original. A deep copy constructs a new compound object and then, recursively, inserts copies into it of the objects found in the original. So, any changes made to the copy do not reflect in the original and any changes made to the original do not reflect in the copy.

All whitespace characters from a string can be removed by using replace method replacing whitespace with null string

Python tuples do not have the sort method. So, to sort the elements of a tuple, the sorted builtin function can be used by passing the tuple as the argument. The function returns a list with the items of tuple sorted in ascending order. This list can be converted into a tuple by using tuple( ) The default sorting order is ascending order. The reverse=True parameter sorts the items in descending order.

String interpolation is the process of evaluating a string literal containing one or more placeholders, yielding a result in which the placeholders are replaced with their corresponding values. There are three common ways to interpolate strings in Python:

Python tuples have two built-in methods:

my_tuple.count(element) will give the number of occurrence of an element in my_tuple

An empty tuple can be created by using tuple constructor, tuple( ) or by using a pair of parentheses with no values in them.
A tuple with just one element (singleton tuple) can be created by using a trailing comma after the object or by using a pair of parentheses with the object in them.
A tuple with more than one element can be created by elements separated by commas or by using a pair of parentheses with the elements separated by commas in them.

del.my_tuple would delete my_tuple

Since tuples are immutable, elements cannot be added/modified/deleted from a tuple.

my_tuple.index(element,start,end) would retun the position of the first occurrence of the element in the tuple and If the element is not found, ValueError is raised.

Python's python inbuilt cmp method can be used to compare two tuples to see if they have the same elements

Yes, tuples can be nested to any depth needed.

tup1 = (1, 2, 3)
tup2 = ('gk', 'nxt')
nested_tuple = (tup1, tup2)

A tuple can be converted into a list by using the list constructor with the tuple as the argument

list(my_tuple)

A list can be converted into a tuple by using the tuple constructor with the list as the argument

tuple(my_list)

Starting with Python 3.7, dictionary is insertion-ordered. So, dict.fromkeys(mylist) will remove the duplicate characters from the string preserving the original order of the characters in the string. Creating a list with the dict keys and joining the individual characters into a string using the join function will give the string with duplicates removed.

magic = 'abracadabra'
''.join(list(dict.fromkeys(magic)))

To remove the duplicate characters from a string and the original order of the string need not be preserved, assigning the string to a set and then converting it back to list and joining the individual characters into a string using the join function will give the string with duplicates removed. (sets will not necessarily maintain the order of characters of the string)

magic = 'abracadabra'
''.join(list(set(magic)))

A list is a mutable, ordered collection of objects. The objects can be of any type and need not be unique. Lists can be constructed by enclosing comma separated objects in a pair of square brackets or by using list constructor, list(iterator). An empty list can be constructed by using a pair of square brackets ([]).

A tuple is an immutable, ordered collection of objects. Python’s creator intended tuples for heterogenous data. Tuples are Python's way of packaging heterogeneous pieces of information in a composite object. For example, socket = ('www.python.org', 80) brings together a string and a number so that the host/port pair can be passed around as a socket, a composite object

In Python, pass is both a keyword and statement. It's just a place-holder and will be ignored by Python as pass requires no action

Yes, but it will create a circular reference

No, python does not support switch or case statement. A set of if-elif-else statements can be used to get that functionality

d, e, f = {}, dict(), dict(())

d['one'] = 1.0; d['two'] = 2.0; d['three'] = 3.0

e = dict([('two', 2/1), ('three', 3/1), ('one', 1/1)])

f = dict(zip(['three', 'one', 'two'], [3, 1, 2]))

print(d == e and e == f and d == f)