Return multiple columns using Pandas apply() method

Objects passed to the pandas.apply() are Series objects whose index is either the DataFrame’s index (axis=0) or the DataFrame’s columns (axis=1). By default (result_type=None), the final return type is inferred from the return type of the applied function. Otherwise, it depends on the result_type argument.

Syntax: DataFrame.apply(func, axis=0, broadcast=None, raw=False, reduce=None, result_type=None, args=(), **kwds)

Below are some programs which depicts the use of pandas.DataFrame.apply()

Example 1:

# Program to illustrate the use of
# pandas.DataFrame.apply() method

# Importing required Libraries
import pandas
import numpy

# Creating dataframe
dataFrame = pandas.DataFrame([[4, 9], ] * 3, columns =['A', 'B'])
print('Data Frame:')
display(dataFrame)

# Using pandas.DataFrame.apply() on the data frame
print('Returning multiple columns from Pandas apply()')
dataFrame.apply(numpy.sqrt)

Output:

Using a numpy universal function (in this case the same as numpy.sqrt(dataFrame)).

Example 2:

# Program to illustrate the use of
# pandas.DataFrame.apply() method

# Importing required Libraries
import pandas
import numpy

# Creating dataframe
dataFrame = pandas.DataFrame([[4, 9], ] * 3, columns =['A', 'B'])
print('Data Frame:')
display(dataFrame)

# Using pandas.DataFrame.apply() on the data frame
print('Returning multiple columns from Pandas apply()')
dataFrame.apply(numpy.sum, axis = 0)

Output:

Using a reducing function on columns.

Example 3:

# Program to illustrate the use of
# pandas.DataFrame.apply() method

# Importing required Libraries
import pandas
import numpy

# Creating dataframe
dataFrame = pandas.DataFrame([[4, 9], ] * 3, columns =['A', 'B'])
print('Data Frame:')
display(dataFrame)

# Using pandas.DataFrame.apply() on the data frame
print('Returning multiple columns from Pandas apply()')
dataFrame.apply(numpy.sum, axis = 1)

Output:

Using a reducing function on rows.

Example 4:

# Program to illustrate the use of
# pandas.DataFrame.apply() method

# Importing required Libraries
import pandas
import numpy

# Creating dataframe
dataFrame = pandas.DataFrame([[4, 9], ] * 3, columns =['A', 'B'])
print('Data Frame:')
display(dataFrame)

# Using pandas.DataFrame.apply() on the data frame
print('Returning multiple columns from Pandas apply()')
dataFrame.apply(lambda x: [1, 2], axis = 1)

Output:

Returning a list-like will result in a Series.

Example 5:

# Program to illustrate the use of
# pandas.DataFrame.apply() method

# Importing required Libraries
import pandas
import numpy

# Creating dataframe
dataFrame = pandas.DataFrame([[4, 9], ] * 3, columns =['A', 'B'])
print('Data Frame:')
display(dataFrame)

# Using pandas.DataFrame.apply() on the data frame
print('Returning multiple columns from Pandas apply()')
dataFrame.apply(lambda x: [1, 2], axis = 1, result_type ='expand')

Output:

Passing result_type=’expand’ will expand list-like results to columns of a Dataframe.

Example 6:

# Program to illustrate the use of
# pandas.DataFrame.apply() method

# Importing required Libraries
import pandas
import numpy

# Creating dataframe
dataFrame = pandas.DataFrame([[4, 9], ] * 3, columns =['A', 'B'])
print('Data Frame:')
display(dataFrame)

# Using pandas.DataFrame.apply() on the data frame
print('Returning multiple columns from Pandas apply()')
dataFrame.apply(lambda x: pandas.Series(
    [1, 2], index =['foo', 'bar']), axis = 1)

Output:

Returning a Series inside the function is similar to passing result_type=’expand’. The resulting column names will be the Series index.

Example 7:

# Program to illustrate the use of
# pandas.DataFrame.apply() method

# Importing required Libraries
import pandas
import numpy

# Creating dataframe
dataFrame = pandas.DataFrame([[4, 9], ] * 3, columns =['A', 'B'])
print('Data Frame:')
display(dataFrame)

# Using pandas.DataFrame.apply() on the data frame
print('Returning multiple columns from Pandas apply()')
dataFrame.apply(lambda x: [1, 2], axis = 1, result_type ='broadcast')

Output:

Passing result_type=’broadcast’ will ensure the same shape result, whether list-like or scalar is returned by the function, and broadcast it along the axis. The resulting column names will be the originals.