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Pandas DataFrame: Count the NaN values in one or more columns in DataFrame

Pandas: DataFrame Exercise-35 with Solution

Write a Pandas program to count the NaN values in one or more columns in DataFrame.

Sample data:
Original DataFrame
attempts name qualify score
0 1 Anastasia yes 12.5
1 3 Dima no 9.0
2 2 Katherine yes 16.5
3 3 James no NaN
4 2 Emily no 9.0
5 3 Michael yes 20.0
6 1 Matthew yes 14.5
7 1 Laura no NaN
8 2 Kevin no 8.0
9 1 Jonas yes 19.0
Number of NaN values in one or more columns:
2

Sample Solution :

Python Code :

import pandas as pd
import numpy as np
exam_data = {'name': ['Anastasia', 'Dima', 'Katherine', 'James', 'Emily', 'Michael', 'Matthew', 'Laura', 'Kevin', 'Jonas'],
        'score': [12.5, 9, 16.5, np.nan, 9, 20, 14.5, np.nan, 8, 19],
        'attempts': [1, 3, 2, 3, 2, 3, 1, 1, 2, 1],
        'qualify': ['yes', 'no', 'yes', 'no', 'no', 'yes', 'yes', 'no', 'no', 'yes']}
df = pd.DataFrame(exam_data)
print("Original DataFrame")
print(df)
print("\nNumber of NaN values in one or more columns:")
print(df.isnull().values.sum())

Sample Output:

      Original DataFrame
   attempts       name qualify  score
0         1  Anastasia     yes   12.5
1         3       Dima      no    9.0
2         2  Katherine     yes   16.5
3         3      James      no    NaN
4         2      Emily      no    9.0
5         3    Michael     yes   20.0
6         1    Matthew     yes   14.5
7         1      Laura      no    NaN
8         2      Kevin      no    8.0
9         1      Jonas     yes   19.0

Number of NaN values in one or more columns:
2

Python-Pandas Code Editor:

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Python: Tips of the Day

Inserting if statements using conditional list comprehensions:

x = [1, 2, 3, 4, 5, 6]
result = []
for idx in range(len(x)):
    if x[idx] % 2 == 0:
        result.append(x[idx] * 2)
    else:
        result.append(x[idx])
result

Output:

[1, 4, 3, 8, 5, 12]

[(element * 2 if element % 2 == 0 else element) for element in x]

Output:

[1, 4, 3, 8, 5, 12]

[element * 2 for element in x if element % 2 == 0]

Output:

[4, 8, 12]