Pandas: Split the specified dataframe into groups and count unique values of 'value' column

Last update on May 28 2022 13:37:32 (UTC/GMT +8 hours)

Pandas Grouping and Aggregating: Split-Apply-Combine Exercise-15 with Solution

Write a Pandas program to split the following dataframe into groups and count unique values of 'value' column.

Test Data:

   id value
0   1     a
1   1     a
2   2     b
3   3  None
4   3     a
5   4     a
6   4  None
7   4     b

Sample Solution:

Python Code :

import pandas as pd
df = pd.DataFrame({
    'id': [1, 1, 2, 3, 3, 4, 4, 4],
    'value': ['a', 'a', 'b', None, 'a', 'a', None, 'b']
})
print("Original DataFrame:")
print(df)
print("Count unique values:")
print (df.groupby('value')['id'].nunique())

Sample Output:

Original DataFrame:
   id value
0   1     a
1   1     a
2   2     b
3   3  None
4   3     a
5   4     a
6   4  None
7   4     b
Count unique values:
value
a    3
b    2
Name: id, dtype: int64

Python Code Editor:

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Previous: Write a Pandas program to split the following dataframe into groups based on all columns and calculate Groupby value counts on the dataframe.
Next: Write a Pandas program to split a given dataframe into groups and list all the keys from the GroupBy object.

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Python: Tips of the Day

Find current directory and file's directory:

To get the full path to the directory a Python file is contained in, write this in that file:

import os 
dir_path = os.path.dirname(os.path.realpath(__file__))

(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)

To get the current working directory use

import os
cwd = os.getcwd()

Documentation references for the modules, constants and functions used above:

The os and os.path modules.
The __file__ constant
os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
os.path.dirname(path) (returns "the directory name of pathname path")
os.getcwd() (returns "a string representing the current working directory")
os.chdir(path) ("change the current working directory to path")

Ref: https://bit.ly/3fy0R6m