Data Science with Python Certification Data Science with Python Pandas DataFrame Operations 2

Question 1

Which method returns the number of non-null values in each column of a DataFrame?

Accepted Answer

df.count()

Answer

df.count() returns the count of non-null values per column by default.

Question 2

What does df.pivot_table(values='sales', index='region', aggfunc='mean') compute?

Accepted Answer

Mean sales per region

Answer

The aggfunc='mean' parameter computes the average of the 'sales' column grouped by 'region'.

Question 3

How do you rename columns 'a' and 'b' to 'x' and 'y' in a DataFrame df?

Accepted Answer

df.rename(columns={'a':'x','b':'y'})

Answer

df.rename(columns={...}) accepts a mapping dict via the columns keyword argument.

Question 4

What is the result of df.duplicated() on a DataFrame?

Accepted Answer

Returns a boolean Series marking duplicate rows

Answer

df.duplicated() returns a boolean Series where True indicates a row is a duplicate of a previous row.

Question 5

Which of the following correctly filters rows where column 'age' is between 18 and 35 (inclusive)?

Accepted Answer

df[df['age'].between(18, 35)]

Answer

The .between(left, right) method returns True for values within the inclusive range.

Data Science with Python Certification Practice Test