计算csv文件中的出现次数

Question

I need to find which year had the most tornadoes occur in LA. I have figured out how to print it, but how would I get it to count and then print the year that had the most tornadoes?

import csv

with open('tornadoes.csv') as csv_file:
    csv_reader = csv.reader(csv_file, delimiter=',')
    line_count = 0
    for row in csv_reader:

        if line_count == 0:
            pass

        else:
            if row[idx['st']]=="LA":
                print(row[idx['st']], row[idx['yr']])

        line_count +=1

Answer 1

You can use the collections.Counter.most_common method:

import csv
from collections import Counter

with open('tornadoes.csv') as csv_file:
    csv_reader = csv.reader(csv_file, delimiter=',')
    next(csv_reader)
    print(Counter(row[idx['yr']] for row in csv_reader if row[idx['st']] == 'LA').most_common())

Answer 2

What you can do is make a dictionary, and have each year as a key. Once you checking your file you can just return the max count.

import csv
import operator

with open('tornadoes.csv') as csv_file:
    csv_reader = csv.reader(csv_file, delimiter=',')

    line_count, num_tornados = 0, {}

    for row in csv_reader:

        if line_count == 0:
            pass

        else:
            if row[idx['st']]=="LA":
                if row[idx['yr']] in num_tornados:
                    num_tornados[row[idx['yr']]] += 1
                else:
                    num_tornados[row[idx['yr']]] = 1

        line_count +=1
    print(max(num_tornados.iteritems(), key=operator.itemgetter(1))[0])