How to Compute Row-wise Mean in Pandas: Two Simple Methods

1. Introduction

Hello, I am Pipipi. A question about processing data with Pandas was posted in a Python group, and this article provides a solution.

2. Original Data

df = pd.DataFrame({
    'student_id': ['S001', 'S002', 'S003'],
    'marks': [[88,89,90],[78,81,60],[84,83,91]]
})
print(df)

The DataFrame contains a column of list‑type marks for each student.

3. Expected Result

4. Method One

Using map with a lambda function:

df['dmean'] = df['marks'].map(lambda x: np.mean(x))
print(df)

5. Method Two

Using map or apply directly with np.mean:

df['dmean'] = df['marks'].map(np.mean)
# or
df['dmean'] = df['marks'].apply(np.mean)
print(df)

6. Conclusion

The article presented a Pandas data‑processing problem and offered two concrete solutions that compute the mean of each student's marks, enabling readers to apply these techniques to similar tasks.