Python Pandas Interview Questions and Answers

Ques 1. What is Pandas in Python?

Pandas is an open-source data manipulation and analysis library for Python.

Ques 2. How do you import the Pandas library?

import pandas as pd

Ques 3. How do you create a DataFrame in Pandas?

pd.DataFrame(data)

Example:

df = pd.DataFrame({'column1': [1, 2, 3], 'column2': ['a', 'b', 'c']})

Ques 4. How do you select specific columns from a DataFrame?

df[['column1', 'column2']]

Ques 5. How can you apply a function to each element in a DataFrame?

Use the apply function. df.apply(my_function)

Ques 6. How can you rename columns in a Pandas DataFrame?

Use the rename function. df.rename(columns={'old_name': 'new_name'})

Ques 7. Explain the difference between Series and DataFrame in Pandas.

A Series is a one-dimensional labeled array, and a DataFrame is a two-dimensional table.

Ques 8. How do you convert a Pandas DataFrame to a NumPy array?

Use the values attribute. df.values

Ques 9. How can you reset the index of a Pandas DataFrame?

Use the reset_index function. df.reset_index()

Ques 10. How do you sort a Pandas DataFrame by a specific column?

Use the sort_values function. df.sort_values(by='column')

Ques 11. What is the purpose of the to_csv function in Pandas?

to_csv is used to write a DataFrame to a CSV file.

Example:

df.to_csv('output.csv', index=False)

Ques 12. How do you check for the existence of a specific value in a Pandas DataFrame?

Use the isin function. df['column'].isin([value])

Ques 13. What is the purpose of the read_csv function in Pandas?

read_csv is used to read data from a CSV file into a DataFrame.

Example:

df = pd.read_csv('file.csv')

Ques 14. Explain the use of the describe function in Pandas.

describe generates descriptive statistics of a DataFrame, excluding NaN values.

Example:

df.describe()

Ques 15. How can you drop columns from a Pandas DataFrame?

Use the drop function. df.drop(['column1', 'column2'], axis=1)

Ques 16. How do you handle duplicate values in a Pandas DataFrame?

Use the drop_duplicates() function. df.drop_duplicates()

Ques 17. Explain the purpose of the to_datetime() function in Pandas.

to_datetime() is used to convert the argument to datetime.

Example:

df['date_column'] = pd.to_datetime(df['date_column'])

Ques 18. How do you change the data type of a Pandas Series or DataFrame column?

Use the astype() function. df['column'] = df['column'].astype('new_dtype')

Ques 19. Explain the purpose of the nlargest() function in Pandas.

nlargest() returns the first n largest elements from a DataFrame or Series.

Example:

df.nlargest(5, 'column')

Ques 20. How can you create a Pandas DataFrame from a dictionary of Series or dictionaries?

Use the pd.DataFrame() constructor. df = pd.DataFrame({'column1': series1, 'column2': series2})

Ques 21. What is the purpose of the to_excel() function in Pandas?

to_excel() is used to write a DataFrame to an Excel file.

Example:

df.to_excel('output.xlsx', index=False)

Ques 22. How do you calculate the correlation matrix for a Pandas DataFrame?

Use the corr() function. df.corr()