pandas

Question 1

Filter rows where column > value

Answer 1

df[df[‘col’] > x]

Question 2

Select rows with multiple conditions

Answer 2

df[(df[‘a’] > 0) & (df[‘b’] == ‘x’)]

Question 3

Create a new column

Answer 3

df[‘total’] = df[‘a’] + df[‘b’]

Question 4

Group by and aggregate

Answer 4

df.groupby(‘cat’)[‘val’].mean()

Question 5

Count rows per group

Answer 5

df.groupby(‘cat’).size()

Question 6

Fill missing values

Answer 6

df[‘x’].fillna(df[‘x’].median())

Question 7

Sort by multiple columns

Answer 7

df.sort_values([‘a’,’b’], ascending=[True,False])

Question 8

Drop duplicates

Answer 8

df.drop_duplicates(subset=’id’)

Question 9

Apply function row-wise

Answer 9

df[‘y’] = df[‘x’].apply(f)

Question 10

Merge DataFrames

Answer 10

df1.merge(df2, on=’id’, how=’left’)