interview questions for data analytics jobs

Python Interview Questions and Answers for Data Analytics Jobs

Table of Contents

What are the built-in types of python?

Python’s built-in types are as follows:

  • Integers
  • Floating-point
  • complex
  • numbers
  • strings
  • booleans
  • built-in
  • functions.

What type of language is Python? Programming or scripting?

Python can be scripted, but it is mostly a programming language for general-purpose use. To learn more about scripting, see the Python scripting tutorial.

What is Python, and why is it popular for programming?

Python is a high-level, interpreted programming language renowned for its readability and flexibility. Its popularity comes from its ease of use, rich library resources, and strong community support.

How do you comment in Python?

To make a single-line comment, use the ‘#’ sign. Triple quotes (”’ or “””) can be used for multiline comments.

What is PEP 8?

PEP 8 (Python Enhancement Proposal 8) is the style guide for Python code, providing conventions on how to format code for better readability.

How do you declare and use variables in Python?

Variables are declared without an explicit type. Example: x = 10; name = “John”.

Explain the purpose of __init__ in Python classes?

__init__ is a Python class method that is used to initialize object attributes when a new instance is created.

What is a list comprehension in Python?

List comprehension is a concise method for creating lists. Example:

[x**2 for x in range(5)].

How do you handle exceptions in Python?

Use try, except blocks. Example:
result = 10 / 0
except ZeroDivisionError:
print(“Cannot divide by zero!”)

What is the purpose of the if __name__ == "__main__": statement?

It indicates whether the Python script is being executed as the main program or imported as a module.

How do you open and read a file in Python?

To open a file, use open(), followed by read(), readline(), or readlines().

What is the difference between list and tuples in Python?


Lists are mutable i.e., they can be edited.Tuples are immutable, meaning they cannot be edited after creation.
Lists are slower than tuples.Tuples are faster than lists.
Syntax: list_1 = [10, ‘Chelsea’, 20]Syntax: tup_1 = (10, ‘Chelsea’, 20)

What are the key features of Python?

  • Python is an interpreted language. This means that, unlike languages such as C and its derivatives, Python does not require compilation before operation. Other interpreted languages include PHP and Ruby.
  • Python is dynamically typed, which means you do not need to specify the types of variables when declaring them. You can use something like x=111 and then x=”I’m a string” without errors.
  • Python is highly suited for object-oriented programming since it supports class definition, composition, and inheritance. Python does not have access specifiers (like C++’s public and private).
  • In Python, functions are considered first-class objects. This means that they can be assigned to variables, returned by other functions, and passed across functions. Classes are also first class objects.
  • Python code is quick to write, but it often runs slower than compiled languages. Python supports C-based extensions, allowing for efficient optimization of bottlenecks. The numpy module is a good illustration of this; it’s extremely fast since much of the number-crunching it performs isn’t done by Python.
  • Python is used in a variety of contexts, including online applications, automation, scientific modeling, big data applications, and many more. It is also commonly used as “glue” code to make other languages and components work together. Learn more about Big Data and its applications with the Azure data engineering training course.

Explain 'if-elif-else' statement in Python.

It is used for conditional branching. If the ‘if’ condition is false, it looks into the ‘elif’ conditions; if none of them are true, it performs the ‘else’ block.

How does a 'for' loop work in Python?

Python’s ‘for’ loop iterates over a sequence (such as a list, tuple, or string) and runs a block of code for each entry. The loop runs until all components are handled. It uses a basic syntax:

for element in sequence:
# code to execute for each element

What is the purpose of 'range()' function in Python?

Python’s ‘range()’ method creates a sequence of integers. It is typically used with ‘for’ loops to iterate over an initial selection of data. The fundamental syntax is:

range(start, stop, step)

start: Optional sequence beginning value (0 is the default).
Stop: Required; produces numbers up to but not including this value.
step: Optional, the difference between each number in the series (default: 1).

Explain the difference between 'return' and 'print' in a function.

‘print’ : displays information on the console for instant reading.
‘return’: Returns a value to the caller, allowing the function to provide an output that may be saved or utilized in further computations.

Libraries for Data Analytics:

What is NumPy?

NumPy is a Python library for numerical operations that supports arrays and matrices, which are required for efficient numerical computations in data analytics and scientific computing.

Explain the purpose of Pandas in Python?

Pandas is a Python library for data manipulation and analysis. It offers data structures like DataFrame for handling and cleaning structured data, making it a powerful tool in data analytics.

What is Matplotlib used for?

Matplotlib is a Python toolkit for producing static, interactive, and animated visualizations. It is frequently used to plot and show data in a variety of ways, which improves data analysis and communication.

what is seaborn used for?

Seaborn is a Python package for visualizing statistical data. It is built on Matplotlib and offers a high-level interface for producing visually appealing and informative statistical charts, making it especially helpful for data analysis and exploration.

What is the difference between 'loc' and 'iloc' in Pandas?

‘loc’: Pandas label-based indexing, which allows you to choose data based on labels or criteria.

‘iloc’: Integer-location based indexing, which is used to pick data based on number indices, similar to regular Python indexing.

Explain the concept of a DataFrame in Pandas.

DataFrame: A two-dimensional, tabular data structure in Pandas. It consists of rows and columns, where each column can have a different data type. It is similar to a spreadsheet or SQL table and is a powerful tool for data manipulation and analysis in Python.

What is the purpose of the 'groupby' function in Pandas?

The ‘groupby’ function in Pandas is used to group rows of a DataFrame based on some criterion (for example, values in a certain column) and then apply a function to each group separately. It is useful for gathering, processing, and evaluating data from specified categories.

How do you handle missing values in a DataFrame using Pandas?

Handling missing values in Pandas DataFrame:

  • Use dropna() to eliminate rows with missing values.
  • Use fillna() to replace missing values with a specific value or statistical measure (e.g., mean or median).

Explain the purpose of the 'apply()' function in Pandas.

The ‘apply()’ method in Pandas is used to apply a function along the axis of a DataFrame or to a single column. It is used for changing data by applying a custom or built-in function to each element, row, or column of the DataFrame.

How can you connect to a SQL database using Python?

  • Use sqlite3 for SQLite databases and SQLAlchemy for other SQL databases.
  • Create a connection with connection parameters such as the database URL, username, and password.
  • Create a cursor to conduct SQL queries and get the results.
    When you’re finished, close the connection.

Explain the Global Interpreter Lock (GIL) in Python.

The Global Interpreter Lock (GIL) in Python is a technique that ensures that only one thread executes Python bytecode at a time. It reduces multi-core consumption in CPU-bound operations while improving memory management and making it easier to utilize Python in a multi-threaded environment for I/O-bound tasks.

Explain the concept of correlation.

Correlation is a statistical term that measures the degree to which two variables change together. The scale goes from -1 to 1, where:

  • 1 indicating a perfect positive correlation, 
  • -1 indicating a perfect negative correlation, and 
  • 0 representing no connection.

What is the difference between mean and median?

  • The mean of a set of values is computed by adding all of the values and dividing by the total number of values.
  • The median is the middle value in a sorted set of values. If the collection has an even number of items, the median is the mean of the two middle values.

What is a probability distribution?

Probability Distribution: Explains the possibility of various outcomes in a statistical experiment. It gives probabilities to each conceivable result, reflecting the likelihood of encountering that occurrence. Common distributions include uniform, normal (Gaussian), and binomial.

Explain the normal distribution?

The Normal Distribution, often known as the Gaussian distribution, is a symmetric, bell-shaped probability distribution. It is defined by the mean (center) and standard deviation (spread). The Central Limit Theorem predicts that many natural events, such as heights or test scores, will follow this distribution.

How do you convert a column to datetime in Pandas?

In Pandas, use the pd.to_datetime() function.
Example: df[‘column_name’] = pd.to_datetime(‘column_name’)
Converts the supplied column to datetime format, which allows Pandas to do various time-related operations.

What is a moving average?

Moving Average: A statistical procedure that analyzes data points by generating a series of averages from various subsets of the entire dataset. It reduces short-term swings and reveals trends or patterns in time series data.

What is TensorFlow used for?

Google developed TensorFlow, an open-source machine learning framework. It is used to create and train deep learning models, making it a versatile platform for a variety of machine learning applications such as neural networks and deep neural networks.

How do you reverse a list in Python?

In Python, you may reverse a list by calling the reverse() function or slicing. Here are the two methods:

  • Using the reverse() method:
  • My_list is [1, 2, 3, 4, 5].reverse()
    Results: [5, 4, 3, 2, 1]
  • Using slicing:
  • my_list: [1, 2, 3, 4, 5]
    Reversed_list = my_list[::-1].
    Results: [5, 4, 3, 2, 1]
  • Both approaches reverse the order of the entries in the list. Choose the one that best suits your coding style or requirements.

What is the difference between append() and extend() methods for lists in Python?

The append() function adds a single entry to the end of a list.

my_list = [1, 2, 3] my_list.append(4)    # Result: [1, 2, 3, 4]

The extend() function adds elements from an iterable (such as a list or tuple) to the end of a list.

my_list = [1, 2, 3] my_list.extend([4, 5]  # Result: [1, 2, 3, 4, 5]

Append() adds a single element, but extend() adds items from an iterable, thereby integrating several entries into the original list.

Explain the difference between 'read()' and 'readline()' methods in file handling.

The read() method returns the whole contents of a file as a single string or bytes.

The readline() method reads one line from a file and returns it as a string. It shifts the pointer to the next line on future calls.

What is the purpose of the 'try', 'except', 'else', and 'finally' blocks in exception handling?

  • Try block: Encloses code that may throw an exception.
  • Except block: Catches and manages exceptions.
  • else block: Executes if there is no exception in the try block.
  • Finally block: Always runs, regardless of whether an exception occurred. Used for clean-up activities.

How do you raise custom exceptions in Python?

Use the raise keyword, then specify the exception type and optional error message.

raise CustomException("This is a custom exception.")

Explain list comprehensions in Python.

  • List comprehensions are a succinct way to generate lists on a single line.
  • Syntax: [Expression for item in iterable if condition].
  • Creates a new list by applying the expression to each item in the iterable that meets the criterion.

What is the purpose of the 'with' statement in Python?

  • List comprehensions are a succinct way to generate lists on a single line.
  • Syntax: [Expression for item in iterable if condition].
  • Creates a new list by applying the expression to each item in the iterable that meets the criterion.

How do you handle and log exceptions in Python?

  • To capture and manage errors, use try/except blocks.
  • Use else for code that executes when there are no exceptions.
  • Use finally for cleaning code that always runs.
  • Use the logging module to record exception data, which will help with debugging and analysis.

What is the purpose of the 'yield' keyword in Python?

  • The ‘yield’ keyword is used in generator functions to create a succession of values.
  • It enables the function to maintain its state in between calls.
  • When the generator function is called, it continues execution from the last ‘yield’ statement.

How does the 'zip()' function work in Python?

  • The ‘zip()’ function converts several iterables (such as lists) into tuples.
  • It generates an iterator of tuples, each containing elements from the respective locations in the input iterables.
  • If the input iterables are of unequal length, ‘zip()’ will cease constructing tuples once the shortest iterable is exhausted.

What is the purpose of the 'map()' function in Python?

  • The’map()’ method performs a defined function on all elements in an input iterable.
  • It returns an iterator of the results, allowing you to easily alter components with a given function.

Explain the purpose of the 'filter()' function in Python.

  • The ‘filter()’ function creates a list (or iterator) from the items of an iterable that return true.
  • It allows you to include objects based on a specific requirement.

What is the difference between 'deep copy' and 'shallow copy' in Python?

  • Shallow Copy: Creates a new object but does not make copies of nested objects. The new object’s references refer to the same nested objects as the original.
import copy 
new_list = copy.copy(original_list)
  • Deep Copy creates a new object and recursively replicates all hierarchical items. The new object exists independently of the original.
import copy
new_list = copy.deepcopy(original_list)

What is the purpose of the 'pass' statement in Python?

  • The ‘pass’ expression represents a null action.
  • It is used as a placeholder when some syntactical code is necessary but no action is requested.
  • Useful for ensuring syntactical completeness in cases where no action is required.

How do you check if a variable is an instance of a particular class in Python?

  • Use the isinstance() function to find out whether a variable is an instance of a given class.
  • Syntax: isinstance(variable, ClassName)
  •  This function returns True if the variable is an instance of the supplied class, and False otherwise.

Explain the purpose of the 'super()' function in Python.

  • The’super()’ function calls a method from a parent class in an inherited class.
  • Method overriding is facilitated, and the child class can invoke its parent class’s method implementation.

What is the purpose of the 'assert' statement in Python?

  • The ‘assert’ statement is used for debugging.
  • If the condition is false, a ‘AssertionError’ is raised, along with an optional error message.
  • It aids in the identification and resolution of challenges during the development process.

What are Python modules?

  • Python modules are files containing Python code that are typically structured into functions, classes, or variables.
  • They allow you to arrange code and build reusable, shareable pieces.
  • Modules can be imported into other Python programs by using the import statement.

How do you handle circular imports in Python?

  • Import the necessary module within the function or method where it is required, rather than at the start of the file.
  • This pauses the import until the function is called, preventing circular imports.

Explain the purpose of the 'init()' method in Python classes.

  • In Python classes, the __init__() function is a specific method that is used to initialize class instances.
  • It is called automatically whenever a new object is created from the class.
  • Sets basic properties and performs setup activities on the object.

Explain the difference between regression and classification.

  • Regression predicts continuous values or numerical outcomes.

For example, predicting housing and stock prices.

  • Classification predicts categorical values or discrete outcomes.

Examples include classifying emails as spam or not spam, and estimating the species of a flower.

What is Scikit-learn used for?

  • Scikit-learn is a machine learning library for Python.
  • It offers simple and effective tools for data mining and analysis.
  • Provides a variety of techniques for classification, regression, clustering, and dimensionality reduction.

What is web scraping, and how is it done with Python?

  • Web scraping is the extraction of data from websites.
  • For Python:
  1. use libraries such as BeautifulSoup or lxml to parse HTML.
  2. Use the requests library to retrieve web pages.
  3. Navigate through the HTML structure to extract the needed information.
  4. Process and save the extracted data as needed.

What is the purpose of the 'requests' library in Python?

  • In Python, the’requests’ package is used to send HTTP requests to receive web content.
  • It makes it easier to send HTTP requests and handle responses.
  • Typically used to interface with APIs or retrieve online pages for web scraping.

How can you connect to a SQL database using Python?

  • Use sqlite3 for SQLite databases and SQLAlchemy for other SQL databases.
  • Create a connection with connection parameters such the database URL, username, and password.
  • Create a cursor to conduct SQL queries and retrieve the results.
  • When you’re finished, close the connection.

What is data privacy, and why is it important in data analytics?

  • Data privacy entails safeguarding personal information and ensuring that sensitive data is handled appropriately.
  • Importance of Data Analytics:
  • Respects individual rights and ethical principles.
  • Increases trust among users and stakeholders.
  • Complies with all legal and regulatory standards.
  • Reduces the likelihood of unauthorized access or misuse of sensitive information.

Explain the purpose of the 'del' statement in Python.

  • Python’s ‘del’ statement is used to delete objects or elements.
  • It can be used to remove a variable, a list item, an object attribute, or a list slice.
  • For example, del my_list[2] removes the element at index 2 of the list.

What is the purpose of the 'reduce()' function in Python, and how is it used?

-‘reduce()’ applies a binary function on an iterable’s items cumulatively.
– For example: from functools import reduce;

result = reduce(lambda x, y: x * y, [1, 2, 3, 4]).

Explain the concept of first-class functions in Python.

  • In Python, functions are first-class citizens, which means they can be regarded as objects like any other data type.
  • The key qualities of first-class functions are:
  1. Functions can be assigned to variables.
  2. Functions can be used as arguments in other functions.
  3. Functions can be returned as values by other functions.
  4. Functions can be stored in data structures such as lists and dictionaries.
  • This flexibility enables sophisticated programming paradigms, such as functional programming and the construction of higher-order functions.

How can you create a recursive function in Python?

  • To define a recursive function in Python, write a function that calls itself within its own body.
  • To avoid infinite loops, include a base case that terminates the recursion.
  • An example of a recursive function for calculating the factorial of a number:
def factorial(n):
if n == 0 or n == 1:
return 1
return n * factorial(n-1)
  • In this example, factorial(n) calls itself using a decreased argument until it hits the base case (n == 0 or n == 1).

Explain the concept of a lambda function in the context of sorting.

  • A lambda function is frequently used as the key argument when specifying custom sorting criteria.
  • The lambda function defines a basic, anonymous function that is tailored to the sorting operation.
  • For example, sort a list of tuples by the second element.
my_list = [(1, 5), (2, 3), (3, 8)]
sorted_list = sorted(my_list, key=lambda x: x[1])
  • The lambda function lambda x: x[1] serves as the key for sorting the tuples based on their second member.

What is the purpose of the 'map()' function, and how is it used?

  • The’map()’ method in Python applies a specified function to all elements in an input iterable (for example, a list) and returns an iterator of the results.
  • Syntax: map (function, iterable).
  • For example, double each element in a list.
my_list = [1, 2, 3, 4]
doubled_list = list(map(lambda x: x * 2, my_list))
  • Here, the lambda function lambda x: x * 2 is applied to each element in my_list using ‘map()’, resulting in doubled_list.
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