Untitled Deck

Question 1

What is the syntax to read a CSV file in pandas?

Answer 1

pd.read_csv(‘filename.csv’)

Question 2

How do you read an Excel file with pandas?

Answer 2

pd.read_excel(‘filename.xlsx’, sheet_name=’Sheet1’)

Question 3

What’s the syntax to save a DataFrame to a CSV file?

Answer 3

df.to_csv(‘filename.csv’, index=False)

Question 4

How do you read a JSON file in pandas?

Answer 4

pd.read_json(‘filename.json’)

Question 5

What parameter sets the column delimiter when reading a CSV?

Answer 5

sep=’,’ or delimiter=’,’

Question 6

How do you create a DataFrame from a dictionary?

Answer 6

pd.DataFrame({‘col1’: [1, 2], ‘col2’: [3, 4]})

Question 7

What’s the syntax to create a Series?

Answer 7

pd.Series([1, 2, 3, 4])

Question 8

How do you create a DatetimeIndex?

Answer 8

pd.date_range(start=’2023-01-01’, periods=10, freq=’D’)

Question 9

How do you create a DataFrame with specific index values?

Answer 9

pd.DataFrame(data, index=[‘a’, ‘b’, ‘c’])

Question 10

What’s the syntax to create a MultiIndex DataFrame?

Answer 10

pd.DataFrame(data, index=pd.MultiIndex.from_tuples([(‘a’, 1), (‘a’, 2), (‘b’, 1)]))

Question 11

How do you select a column from a DataFrame?

Answer 11

df[‘column_name’] or df.column_name

Question 12

What’s the difference between loc and iloc?

Answer 12

loc uses labels for indexing, iloc uses integer positions

Question 13

How do you select rows 5 through 10 with iloc?

Answer 13

df.iloc[5:11]

Question 14

How do you select rows where column ‘A’ > 5?

Answer 14

df[df[‘A’] > 5] or df.loc[df[‘A’] > 5]

Question 15

How do you select the first 5 rows of a DataFrame?

Answer 15

df.head(5) or df.iloc[:5]

Question 16

How do you drop rows with missing values?

Answer 16

df.dropna()

Question 17

How do you fill missing values with a specific value?

Answer 17

df.fillna(value)

Question 18

How do you drop duplicate rows?

Answer 18

df.drop_duplicates()

Question 19

How do you replace all instances of ‘old_value’ with ‘new_value’?

Answer 19

df.replace(‘old_value’, ‘new_value’)

Question 20

How do you check for missing values in a DataFrame?

Answer 20

df.isna() or df.isnull()

Question 21

What’s the syntax for applying a function to each element in a DataFrame?

Answer 21

df.applymap(func)

Question 22

How do you apply a function to each column in a DataFrame?

Answer 22

df.apply(func)

Question 23

How do you apply a function to each element in a Series?

Answer 23

series.map(func)

Question 24

How do you rename columns in a DataFrame?

Answer 24

df.rename(columns={‘old_name’: ‘new_name’})

Question 25

How do you convert a column's data type?

Answer 25

df['column'] = df['column'].astype('int64')

Question 26

What's the basic syntax for a GroupBy operation?

Answer 26

df.groupby('column').agg({'target_column': 'mean'})

Question 27

How do you calculate column means in a DataFrame?

Answer 27

df.mean() or df.mean(axis=0)

Question 28

How do you calculate row sums in a DataFrame?

Answer 28

df.sum(axis=1)

Question 29

How do you get descriptive statistics for a DataFrame?

Answer 29

df.describe()

Question 30

How do you create a pivot table in pandas?

Answer 30

pd.pivot_table(df, values='D', index=['A', 'B'], columns=['C'])

Question 31

How do you concatenate two DataFrames vertically?

Answer 31

pd.concat([df1, df2], axis=0)

Question 32

How do you merge two DataFrames on a common column?

Answer 32

pd.merge(df1, df2, on='common_column')

Question 33

What's the syntax for a left join in pandas?

Answer 33

pd.merge(df1, df2, on='key', how='left')

Question 34

How do you join DataFrames using their indices?

Answer 34

pd.merge(df1, df2, left_index=True, right_index=True)

Question 35

How do you concatenate DataFrames horizontally?

Answer 35

pd.concat([df1, df2], axis=1)

Question 36

How do you resample a time series to monthly frequency?

Answer 36

df.resample('M').mean()

Question 37

How do you create a DatetimeIndex from a string column?

Answer 37

df['date'] = pd.to_datetime(df['date_str'])

Question 38

How do you set a datetime column as index?

Answer 38

df.set_index('date_column', inplace=True)

Question 39

How do you get the year from a datetime column?

Answer 39

df['date'].dt.year

Question 40

How do you calculate the difference between two dates?

Answer 40

(df['end_date'] - df['start_date']).dt.days

Question 41

How do you perform a rolling window calculation?

Answer 41

df.rolling(window=3).mean()

Question 42

What's the syntax for creating a crosstab?

Answer 42

pd.crosstab(df['A'], df['B'])

Question 43

How do you reshape data from wide to long format?

Answer 43

pd.melt(df, id_vars=['A'], value_vars=['B', 'C'])

Question 44

How do you create dummies (one-hot encoding) from a categorical column?

Answer 44

pd.get_dummies(df['category_column'])

Question 45

How do you calculate correlation between columns?

Answer 45

df.corr()

Question 46

How do you display all columns of a DataFrame?

Answer 46

pd.set_option('display.max_columns', None)

Question 47

What method shows basic information about a DataFrame?

Answer 47

df.info()

Question 48

How do you check the memory usage of a DataFrame?

Answer 48

df.memory_usage(deep=True)

Question 49

How do you reset a DataFrame's index?

Answer 49

df.reset_index()

Question 50

How do you save a DataFrame to an HDF5 store?

Answer 50

df.to_hdf('store.h5', key='df')