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GroupBy results to dictionary of lists

Given a pandas dataframe, we have groupby results to dictionary of lists.
Submitted by Pranit Sharma, on September 13, 2022

Prerequisite

• Pandas: 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.
• Dictionaries: Dictionaries are used to store heterogeneous data. The data is stored in key:value pair. A dictionary is a collection that is mutable and ordered in nature and does not allow duplicates which means there are unique keys in a dictionary. A dictionary key can have any type of data as its value, for example, a list, tuple, string, or dictionary itself.
• groupby() Method: The groupby() is a simple but very useful concept in pandas. By using groupby, we can create a grouping of certain values and perform some operations on those values.

Problem statement

Suppose, we have a DataFrame with some columns, we need to perform groupby on a column and store the result in the form of a dictionary.

GroupBy results to dictionary of lists

The groupby() function split the object, apply some operations, and then combines them to create a group hence a large amount of data and computations can be performed on these groups.

Let us understand with the help of an example,

Python program to groupby results to dictionary of lists

# Importing pandas package
import pandas as pd

# Creating a dictionary
d = {
    'A':[1,1,1,2,3,3,4,4],
    'B':[1020,3040,5060,7080,90100,100110,110120,120130],
    'C':[1,1,2,3,4,2,5,5]
}

# Creating a DataFrame
df = pd.DataFrame(d)

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

# Getting group values and 
# converting to dictionary
dictionary = df.groupby('A')['C'].apply(list).to_dict()

# Display result
print("Result:\n",dictionary)

Output

The output of the above program will be:

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