Python algorithm of counting occurrence of specific word in csv

Question

I've just started to learn python. I'm curious about what are the efficient ways to count the occurrence of a specific word in a CSV file, other than simply use for loop to go through line by line and read.

To be more specific, let's say I have a CSV file contain two columns, "Name" and "Grade", with millions of records.

How would one count the occurrence of "A" under "Grade"?

Python code samples would be greatly appreciated!

Answer 1

Basic example, with using csv and collections.Counter (Python 2.7+) from standard Python libraly:

import csv
import collections

grades = collections.Counter()
with open('file.csv') as input_file:
    for row in csv.reader(input_file, delimiter=';'):
        grades[row[1]] += 1

print 'Number of A grades: %s' % grades['A']
print grades.most_common()

Output (for small dataset):

Number of A grades: 2055
[('A', 2055), ('B', 2034), ('D', 1995), ('E', 1977), ('C', 1939)]