Write a program in Python to read CSV data from a file and print the total sum of last two rows

When working with CSV files in Python, you often need to perform calculations on specific rows. This tutorial shows three different methods to read CSV data and calculate the sum of the last two rows using pandas.

Sample CSV Data

First, let's create a sample CSV file named pandas.csv:

Id,Data
1,11
2,22
3,33
4,44
5,55
6,66
7,77
8,88
9,99
10,100

Using tail() Method

The tail() method returns the last n rows of a DataFrame. Combined with sum(), it provides a clean solution ?

import pandas as pd

# Read CSV file
data = pd.read_csv('pandas.csv')
df = pd.DataFrame(data)

print("DataFrame is:")
print(df)
print("\nSum of last two rows:")
print(df.tail(2).sum())

DataFrame is:
   Id  Data
0   1    11
1   2    22
2   3    33
3   4    44
4   5    55
5   6    66
6   7    77
7   8    88
8   9    99
9  10   100

Sum of last two rows:
Id      19
Data   199
dtype: int64

Using iloc Indexing

The iloc[-2:] slice selects the last two rows using negative indexing ?

import pandas as pd

# Read CSV file
data = pd.read_csv('pandas.csv')
df = pd.DataFrame(data)

print("DataFrame is:")
print(df)
print("\nSum of last two rows:")
print(df.iloc[-2:].sum())

DataFrame is:
   Id  Data
0   1    11
1   2    22
2   3    33
3   4    44
4   5    55
5   6    66
6   7    77
7   8    88
8   9    99
9  10   100

Sum of last two rows:
Id      19
Data   199
dtype: int64

Using Loop with Conditional Logic

This manual approach iterates through the DataFrame and identifies the last two rows ?

import pandas as pd

# Read CSV file
data = pd.read_csv('pandas.csv')
df = pd.DataFrame(data)

id_sum = 0
data_sum = 0

for i in range(len(df)):
    if i == len(df) - 2 or i == len(df) - 1:
        id_sum = id_sum + df.iloc[i][0]
        data_sum = data_sum + df.iloc[i][1]

print("Id:", id_sum)
print("Data:", data_sum)

Id: 19
Data: 199

Comparison

Conclusion

Use tail(2).sum() or iloc[-2:].sum() for simple summation tasks as they are more readable and efficient. The loop method is useful when you need custom logic for row processing.