How to Apply a function to multiple columns in Pandas?

Pandas.apply allow the users to pass a function and apply it on every single value of the Pandas series.

Syntax of pandas.DataFrame.apply

Syntax : DataFrame.apply(parameters)

Parameters : 

• func : Function to apply to each column or row.
• axis : Axis along which the function is applied
• raw : Determines if row or column is passed as a Series or ndarray object.
• result_type : ‘expand’, ‘reduce’, ‘broadcast’, None; default None
• args : Positional arguments to pass to func in addition to the array/series.
• **kwds : Additional keyword arguments to pass as keywords arguments to func.

Returns : Series or DataFrame  

Example 1: Pandas Apply Function to Single Column

In this example, we are passing only a single column and increment age with 2.

Python3

# import the module
import pandas as pd

# creating a DataFrame
df = pd.DataFrame({'String 1': ['Tom', 'Nick', 'Krish', 'Jack'],
                   'Age': [32, 24, 33, 21]})

# function for prepending 'Geek'
def prepend_geek(age):
    return age + 2

# executing the function
df[["Age"]] = df[["Age"]].apply(prepend_geek)

# displaying the DataFrame
display(df)

Output:

Example 2: Pandas Apply Function to multiple Columns

Here, we apply a function to two columns of Pandas Dataframe using Python concatenation.

Python3

# import the module
import pandas as pd

# creating a DataFrame
df = pd.DataFrame({'String 1' :['Tom', 'Nick', 'Krish', 'Jack'],
                   'String 2' :['Jane', 'John', 'Doe', 'Mohan']})

# function for prepending 'Geek'
def prepend_geek(name):
    return 'Geek ' + name

# executing the function
df[["String 1", "String 2"]] = df[["String 1",
                                   "String 2"]].apply(prepend_geek)

# displaying the DataFrame
display(df)

Output :

Example 3: Pandas Apply Function to All Columns

Here, we are multiplying all the columns by 2 by calling the multiply_by_2 function.

Python3

# import the module
import pandas as pd

# creating a DataFrame
df = pd.DataFrame({'Integers' :[1, 2, 3, 4, 5],
                   'Float' :[1.1, 2.2, 3.3, 4.4 ,5.5],
                  "Even_no":[2, 4, 6, 8, 10]})

# function for prepending 'Geek'
def multiply_by_2(number):
    return 2 * number

# executing the function
df = df.apply(multiply_by_2)

# displaying the DataFrame
display(df)

Output : 

Example 4: Pandas Apply Function to single Columns using Numpy

In this example, we are applying panda’s apply function to only a single column i.e. Integers, and making it square using numpy.square.

Python3

# import the module
import pandas as pd
import numpy as np

# creating a DataFrame
df = pd.DataFrame({'Integers' :[1, 2, 3, 4, 5],
                   'Float' :[1.1, 2.2, 3.3, 4.4 ,5.5],
                  "Even_no":[2, 4, 6, 8, 10]})

# executing the function
df["Integers"] = df["Integers"].apply(np.square)

# displaying the DataFrame
display(df)

Example 5: Pandas Apply Function to All Columns using lambda

In this example, we are applying panda’s apply function to all the columns, and adding all the columns with 5 using Python lambda.

Python3

# import the module
import pandas as pd

# creating a DataFrame
df = pd.DataFrame({'Integers' :[1, 2, 3, 4, 5],
                   'Float' :[1.1, 2.2, 3.3, 4.4 ,5.5],
                  "Even_no":[2, 4, 6, 8, 10]})

# executing the function
df = df.apply(lambda x: x+5)

# displaying the DataFrame
display(df)