在csv文件python中获取另一列的一列的值

debugcn 发表于 Dev

穆罕默德·沙巴兹·汗（Mohammad Shahbaz Khan）

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

我想通过“ ID”列获取“值”或“金额”列的总和。我想要输出“ A”，它应该给我所有与A均值[3 + 4 + 3]相关的值之和。

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()

姆霍克

您可以使用defaultdictoflist来按ID列对数据进行分组。然后使用sum()产生总计。

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：总和= 10，平均= 3.33 
C：总和= 5，平均= 5.00 
B：总和= 13，平均= 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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