40+ Interview Questions and Answers

Retrieve top 2 cities per state based on max number in third column of pandas dataframe.

• Group the dataframe by state column

• Sort each group by the third column in descending order

• Retrieve the top 2 rows of each group using head(2) function

• Concatenate the resulting dataframes using pd.concat() function

Fill the 3L jar and pour it into the 5L jar. Repeat the process with 3L jar and stop when 5L jar has 4L water.

• Fill 3L jar and pour it into 5L jar

• Repeat the process until 5L jar has 4L water

• 4L can be measured by filling 3L jar twice and pouring it into 5L jar until it reaches 4L

To retain special characters in pandas data, use encoding parameter while reading the data.

• Use encoding parameter while reading the data in pandas

• Specify the encoding type of the data file

• Example: pd.read_csv('filename.csv', encoding='utf-8')

The resultant table will have all the columns from both tables and the rows will be a combination of matching rows.

• The resultant table will have all the columns from both tables

• The rows in the resultant table will be a combination of matching rows

• If the second table has repeated keys, there will be multiple rows with the same key in the resultant table

Use pandas' read_csv() method with appropriate parameters to read large .csv files quickly.

• Use the chunksize parameter to read the file in smaller chunks

• Use the low_memory parameter to optimize memory usage

• Use the dtype parameter to specify data types for columns

• Use the usecols parameter to read only necessary columns

• Use the skiprows parameter to skip unnecessary rows

• Use the nrows parameter to read only a specific number of rows

• Use the na_values parameter to specify values to...read more

my_list[5] retrieves the 6th element of the list.

• Indexing starts from 0 in Python.

• The integer inside the square brackets is the index of the element to retrieve.

• If the index is out of range, an IndexError is raised.

Lambda functions are anonymous functions used for short and simple operations. They are different from regular functions in their syntax and usage.

• Lambda functions are defined without a name and keyword 'lambda' is used to define them.

• They can take any number of arguments but can only have one expression.

• They are commonly used in functional programming and as arguments to higher-order functions.

• Lambda functions are often used for short and simple operations that do not requir...read more

To create dictionaries in Python with repeated keys, use defaultdict from the collections module.

• Import the collections module

• Create a defaultdict object

• Add key-value pairs to the dictionary using the same key multiple times

• Access the values using the key

• Example: from collections import defaultdict; d = defaultdict(list); d['key'].append('value1'); d['key'].append('value2')

Eigenvalues and eigenvectors are linear algebra concepts used in machine learning for dimensionality reduction and feature extraction.

• Eigenvalues represent the scaling factor of the eigenvectors.

• Eigenvectors are the directions along which a linear transformation acts by stretching or compressing.

• In machine learning, eigenvectors are used for principal component analysis (PCA) to reduce the dimensionality of data.

• Eigenvalues and eigenvectors are also used in image processing f...read more

Use vectorized operations, avoid loops, and optimize memory usage.

• Use vectorized operations like apply(), map(), and applymap() instead of loops.

• Avoid using iterrows() and itertuples() as they are slower than vectorized operations.

• Optimize memory usage by using appropriate data types and dropping unnecessary columns.

• Use inplace=True parameter to modify the DataFrame in place instead of creating a copy.

• Use the pd.eval() function to perform arithmetic operations on large DataFr...read more

PCA is a dimensionality reduction technique used to transform high-dimensional data into a lower-dimensional space.

• PCA can be used for feature extraction, data visualization, and noise reduction.

• PCA cannot be used for causal inference or to handle missing data.

• PCA assumes linear relationships between variables and may not work well with non-linear data.

• PCA can be applied to various fields such as finance, image processing, and genetics.

Data analytics allows me to use my technical skills to solve business problems and make data-driven decisions.

• Data analytics helps me to identify patterns and trends in data that can be used to improve business processes.

• It allows me to work with large datasets and use statistical methods to extract insights.

• I can use my technical skills to develop and implement data models and algorithms.

• Data analytics is a growing field with many opportunities for career advancement.

• Example...read more

We minimize the loss in logistic regression.

• The goal of logistic regression is to minimize the loss function.

• The loss function measures the difference between predicted and actual values.

• The optimization algorithm tries to find the values of coefficients that minimize the loss function.

• Minimizing the loss function leads to better model performance.

• Examples of loss functions used in logistic regression are cross-entropy and log loss.

No, two diodes in series cannot work as a transistor.

• Transistors have three terminals while diodes have two.

• Transistors can amplify signals while diodes cannot.

• Transistors can be used as switches while diodes cannot.

• Diodes in series will only increase the voltage drop.

• Transistors have different modes of operation such as common emitter, common base, and common collector.

I am excited to join Affine Analytics because of their reputation for delivering innovative solutions and their focus on employee growth.

• Affine Analytics has a strong track record of delivering cutting-edge solutions to clients across industries.

• I am impressed by the company's commitment to employee growth and development, as evidenced by their training and mentorship programs.

• I am excited about the opportunity to work with a talented and diverse team of professionals at Affi...read more

One vs Rest is a technique used to extend binary classification to multi-class problems in logistic regression.

• It involves training multiple binary classifiers, one for each class.

• In each classifier, one class is treated as the positive class and the rest as negative.

• The class with the highest probability is predicted as the final output.

• It is also known as one vs all or one vs others.

• Example: In a 3-class problem, we train 3 binary classifiers: class 1 vs rest, class 2 vs re...read more

Tree Map visualizes hierarchical data using nested rectangles, while Heatmap displays data values using color gradients.

• Tree Map displays data hierarchically with nested rectangles, where the size and color represent different measures.

• Heatmap visualizes data values using color gradients, with darker colors indicating higher values.

• Tree Map is useful for showing hierarchical data structures, while Heatmap is effective for comparing values across categories.

• Example: Tree Map c...read more

Extract Data saves a snapshot of data in Tableau workbook, while Live Connection directly connects to data source.

• Extract Data creates a static copy of data in Tableau workbook, while Live Connection directly queries data source in real-time.

• Extract Data is useful for working offline or with small datasets, while Live Connection is ideal for large datasets or when data is frequently updated.

• Extract Data can improve performance as it reduces the need to query the data source r...read more

One vs one classification is a binary classification method where multiple models are trained to classify each pair of classes.

• It is used when there are more than two classes in the dataset.

• It involves training multiple binary classifiers for each pair of classes.

• The final prediction is made by combining the results of all the binary classifiers.

• Example: In a dataset with 5 classes, 10 binary classifiers will be trained for each pair of classes.

VIF stands for Variance Inflation Factor, a measure of multicollinearity in regression analysis.

• VIF is calculated for each predictor variable in a regression model.

• It measures how much the variance of the estimated regression coefficient is increased due to multicollinearity.

• A VIF of 1 indicates no multicollinearity, while a VIF greater than 1 indicates increasing levels of multicollinearity.

• VIF is calculated as 1 / (1 - R^2), where R^2 is the coefficient of determination fro...read more

AIC & BIC are statistical measures used to evaluate the goodness of fit of a linear regression model.

• AIC stands for Akaike Information Criterion and BIC stands for Bayesian Information Criterion.

• Both AIC and BIC are used to compare different models and select the best one.

• AIC penalizes complex models less severely than BIC.

• Lower AIC/BIC values indicate a better fit of the model to the data.

• AIC and BIC can be calculated using the log-likelihood function and the number of param...read more

I play badminton twice a week as a hobby.

• I enjoy playing badminton as a way to stay active and relieve stress.

• I usually play with friends or family members at a local community center.

• I have been playing badminton for several years and have improved my skills over time.

The Python code to get the output string as 'jareen arpohc' from the input string 'neeraj chopra' is provided.

• Split the input string into individual words

• Reverse each word

• Join the reversed words with a space in between

Generators are functions that allow you to iterate over a sequence of values without creating the entire sequence in memory. Decorators are functions that modify the behavior of other functions.

• Generators use the yield keyword to return values one at a time

• Generators are memory efficient and can handle large datasets

• Decorators are functions that take another function as input and return a modified version of that function

• Decorators can be used to add functionality to existing...read more

The order of execution of an SQL query involves multiple steps to retrieve data from a database.

• 1. Parsing: The SQL query is first parsed to check for syntax errors.

• 2. Optimization: The query optimizer creates an execution plan to determine the most efficient way to retrieve data.

• 3. Compilation: The optimized query is compiled into an executable form.

• 4. Execution: The compiled query is executed by the database engine to retrieve the requested data.

• 5. Fetching: The retrieved d...read more

Data Validation in Excel ensures that data entered in a cell meets certain criteria or conditions.

• Data Validation allows you to set rules for what can be entered in a cell, such as a range of values, a list of items, or a custom formula.

• Examples of Data Validation include setting a drop-down list of options for a cell, restricting input to a certain number range, or ensuring dates are entered in a specific format.

• Data Validation helps maintain data accuracy and consistency in...read more

A puzzle involving a revolver with 2 bullets.

• The puzzle involves a revolver with 2 bullets and a person who spins the chamber and pulls the trigger twice.

• The question usually asks what is the probability of the person surviving or getting shot.

• The answer depends on the number of chambers in the revolver and whether the bullets are in consecutive chambers or not.

Joins in SQL are used to combine rows from two or more tables based on a related column between them.

• Types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN

• INNER JOIN returns rows when there is at least one match in both tables

• LEFT JOIN returns all rows from the left table and the matched rows from the right table

• RIGHT JOIN returns all rows from the right table and the matched rows from the left table

• FULL JOIN returns rows when there is a match in one of the t...read more

SQL is used in various domains for data analysis and reporting. Use cases include financial analysis, inventory management, and customer relationship management.

• Financial analysis - using SQL to analyze revenue, expenses, and profitability

• Inventory management - tracking stock levels, orders, and shipments

• Customer relationship management - analyzing customer data, preferences, and interactions

Code to list even numbers from a given list of 10 numbers.

• Loop through the list of numbers

• Check if each number is even using the modulo operator

• If the number is even, add it to a new list of even numbers

• Return the new list of even numbers

A pivot table in Excel is a data summarization tool that allows you to reorganize and summarize selected columns and rows of data.

• Pivot tables allow you to analyze and summarize large amounts of data in a spreadsheet.

• You can easily rearrange the layout of the data to view it from different perspectives.

• Pivot tables can perform functions like sum, average, count, and more on the data.

• They are useful for creating reports, charts, and dashboards based on the summarized data.

• For ...read more

Merge and join are used to combine dataframes in pandas.

• Merge is used to combine dataframes based on a common column or index.

• Join is used to combine dataframes based on their index.

• Merge can handle different column names, while join cannot.

• Merge can handle different types of joins (inner, outer, left, right), while join only does inner join by default.

DROP deletes the table structure and data, while TRUNCATE deletes only the data.

• DROP statement removes the table from the database, including all data and structure.

• TRUNCATE statement removes all data from the table, but keeps the table structure intact.

• DROP is a DDL (Data Definition Language) command, while TRUNCATE is a DML (Data Manipulation Language) command.

Reversing a string in Python code

• Use slicing to reverse the string

• Use the built-in function 'reversed()'

• Convert the string to a list, reverse it, and then join it back to a string

R-squared value is a statistical measure that represents the proportion of the variance in the dependent variable that is predictable from the independent variable(s).

• R-squared value ranges from 0 to 1, with 1 indicating a perfect fit.

• It is used to evaluate the goodness of fit of a regression model.

• A higher R-squared value indicates that the model explains a larger proportion of the variance in the dependent variable.

• For example, an R-squared value of 0.8 means that 80% of th...read more

I have worked on various types of data sets including sales data, customer data, financial data, and social media data.

• Sales data

• Customer data

• Financial data

• Social media data

Primary key uniquely identifies each record in a table, while Unique key allows only unique values but can have null values.

• Primary key enforces uniqueness and not null constraint on a column

• Primary key can consist of multiple columns

• Unique key allows only unique values but can have null values

• Unique key can be applied to multiple columns as well

Use conditional formatting to highlight odd cells in Excel

• Select the range of cells you want to highlight

• Go to the 'Home' tab and click on 'Conditional Formatting'

• Choose 'New Rule' and select 'Use a formula to determine which cells to format'

• Enter the formula '=MOD(A1,2)=1' (assuming A1 is the top-left cell of your selected range)

• Choose the formatting style you want for the odd cells

Use window function to calculate running sum of salary in SQL

• Use window function like SUM() with OVER() clause

• Partition the data by employee ID if needed

• Order the data by date or any other relevant column

I have used various transformations such as filtering, joining, aggregating, and pivoting in my data engineering projects.

• Filtering data based on certain conditions

• Joining multiple datasets together

• Aggregating data to summarize information

• Pivoting data from rows to columns or vice versa

Activity life cycle is a crucial concept in Android development. Factorial and Fibonacci series are common mathematical problems. lateinit var and lazy are used for initializing variables. Var and val are used for declaring variables.

• Activity life cycle includes methods like onCreate, onStart, onResume, onPause, onStop, onDestroy.

• Factorial is the product of all positive integers up to a given number. Example: 5! = 5*4*3*2*1 = 120.

• Fibonacci series is a sequence where each numb...read more

A stored procedure is a set of SQL statements that are stored in a database and can be called by other programs or scripts.

• Stored procedures can improve performance by reducing network traffic and executing complex operations on the database server.

• They can be used to encapsulate business logic and enforce security measures.

• Example: CREATE PROCEDURE GetCustomerOrders AS SELECT * FROM Orders WHERE CustomerID = @CustomerID;

Dual mode in Power BI allows users to switch between DirectQuery and Import modes for data sources.

• Dual mode allows users to combine the benefits of both DirectQuery and Import modes in Power BI.

• Users can switch between DirectQuery and Import modes for different data sources within the same report.

• DirectQuery mode connects directly to the data source for real-time data retrieval, while Import mode loads data into Power BI for faster performance.

• For example, users can use Dire...read more

Calculate delta sales growth using DAX formula

• Use the following DAX formula: Delta Sales Growth = (SUM(Sales[SalesAmount]) - CALCULATE(SUM(Sales[SalesAmount]), PREVIOUSMONTH('Date'[DateKey]))) / CALCULATE(SUM(Sales[SalesAmount]), PREVIOUSMONTH('Date'[DateKey]))

• Make sure to replace 'Sales[SalesAmount]' with the actual column name in your dataset

• Ensure that 'Date'[DateKey]' is the date column in your dataset

Accounts payable is the amount of money a company owes to its suppliers or vendors for goods or services purchased on credit.

• Accounts payable is a liability on the balance sheet

• It represents the amount owed by the company to its creditors

• It is typically recorded when goods or services are received but payment has not yet been made

• Examples include invoices from suppliers for inventory purchases or services rendered

Joining tables with different joins in SQL

• Use INNER JOIN to return rows when there is at least one match in both tables

• Use LEFT JOIN to return all rows from the left table and the matched rows from the right table

• Use RIGHT JOIN to return all rows from the right table and the matched rows from the left table

• Use FULL JOIN to return rows when there is a match in one of the tables