import csv
from decimal import *def mean(data_set):return Decimal(sum(data_set)) / len(data_set)def variance(data_set):mean_res = mean(data_set)differences = []squared_res = []for elem in data_set:differences.append(elem - mean_res)for elem in differences:squared_res.append(elem ** 2)return mean(squared_res)def standard_deviation(data_set):variance_res = variance(data_set)return variance_res ** Decimal('0.5')if __name__ == "__main__":with open("dog_data.csv", "r") as csv_file:csv_reader = csv.reader(csv_file)height_data = []for row in csv_reader:height_data.append(int(row[1]))print "Mean: {}".format(mean(height_data))print "Variance: {}".format(variance(height_data))print "Standard Deviation:{}".format(standard_deviation(height_data))

Here I'm getting an ValueError: invalid literal for int() with base 10: 'Height (mm)'.. What does this mean? How do i tackle this error ?

I think your problem is that you read the header (first line) which contain words, and you try to parse it as int.

Try to add

next(csv_reader, None)

Before your loop to skip first row.

As to "How do I tackle that error", for next time simply use print:

print row[1]

Right before the line that produced the error. See what you actually try to convert to int..