Pandas, Future Warning: Indexing with multiple keys

Learn, how can we get rid of the Pandas, Future Warning: Indexing with multiple keys?
Submitted by Pranit Sharma, on September 17, 2022

Pandas is a special tool that allows us to perform complex manipulations of data effectively and efficiently. Inside pandas, we mostly deal with a dataset in the form of DataFrame. DataFrames are 2-dimensional data structures in pandas. DataFrames consist of rows, columns, and data.

Future Warning: Indexing with multiple keys

Pandas usually throw a Future Warning on applying a function to multiple columns of a groupby object. It also suggests to use a list as index instead of tuples.

Also, it sometimes raises a key error if we use multiple columns of groupby object.

Python code to demonstrate Pandas, Future Warning: Indexing with multiple keys

# Importing pandas package
import pandas as pd

# Creating dictionary
d = {'col':[[10,20,30],[11,12,13],[21,22,23]]}

# Creating DataFrame
df = pd.DataFrame(d)

# Display Original DataFrames
print("Created DataFrame:\n",df,"\n")

# Applying groupby
df.groupby([0,1])[1,2].apply(sum)

Output:

Example 1: Future Warning: Indexing with multiple keys

How to fix Future Warning: Indexing with multiple keys?

To get rid of this error, we need to use double brackets after the groupby method. Single brackets are used to output a Pandas Series and double brackets are used to output a Pandas DataFrame.

Let us understand with the help of an example,

Python code to fix Pandas, Future Warning: Indexing with multiple keys

# Importing pandas package
import pandas as pd

# Creating dictionary
d = {'col':[[10,20,30],[11,12,13],[21,22,23]]}

# Creating DataFrame
df = pd.DataFrame(d)

# Display Original DataFrames
print("Created DataFrame:\n",df,"\n")

# Applying groupby
res = df.groupby('col')

# Display result
print(res)