[英]get value of one column by another column in csv file python
我有这样的 csv 文件:
ID Value Amount
---- ------- -------
A 3 2
A 4 4
B 3 6
C 5 5
A 3 2
B 10 1
我想要“ID”列的“值”或“金额”列的总和。 我想要'A'的输出,它应该给我与A相关的所有值的总和意味着[3+4+3]。
我的代码:
import csv
file = open(datafile.csv)
rows=csv.DictReader(file)
summ=0.0
count=0
for r in rows:
summ=summ+int(r['Value'])
count=count+1
print "Mean for column Value is: ",(summ/count)
file.close()
您可以使用list
的defaultdict
按 ID 列对数据进行分组。 然后使用sum()
生成总计。
from collections import defaultdict
with open('datafile.csv') as f:
d = defaultdict(list)
next(f) # skip first header line
next(f) # skip second header line
for line in f:
id_, value, amount = line.split()
d[id_].append((int(value), int(amount)))
# sum and average of column Value by ID
for id_ in d:
total = sum(t[0] for t in d[id_])
average = total / float(len(d[id_]))
print('{}: sum = {}, avg = {:.2f}'.format(id_, total, average))
输入数据的输出:
A: sum = 10, avg = 3.33 C: sum = 5, avg = 5.00 B: sum = 13, avg = 6.50
也可以使用标准的 Python 字典来完成。 解决方案非常相似:
with open('datafile.csv') as f:
d = {}
next(f) # skip first header line
next(f) # skip second header line
for line in f:
id_, value, amount = line.split()
d[id_] = d.get(id_, []) + [(int(value), int(amount))]
# sum and average of column Value by ID
for id_ in d:
total = sum(t[0] for t in d[id_])
average = total / float(len(d[id_]))
print('{}: sum = {}, avg = {:.2f}'.format(id_, total, average))
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