在csv文件python中通过另一列获取一列的值

我的csv文件如下所示：

ID        Value      Amount 
----      -------    -------
A           3          2
A           4          4
B           3          6
C           5          5
A           3          2
B           10         1

我想要“Value”或“Amount”列与“ID”列之和。我想要的输出是，对于“A”，它应该给我所有与平均值[3+4+3]相关的值的总和

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

---

我不想使用收藏。@mohammadshahbazKhan:真的吗？为什么不呢？我正在清理python的基本技能。我试图找出不使用集合的方法。字典算“集合”吗？名单呢？如果没有诸如数据结构之类的集合，要做到这一点非常困难。您可以使用字典或列表。

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))