Question

我有一些这样的数据：

FeatureName,Machine,LicenseHost
Feature1,host1,lichost1
Feature1,host2,lichost1
Feature2,host1,lichost2
Feature1,host1,lichost1

依旧......

我想维护一个嵌套字典，其中第一级密钥是功能名称，其次是计算机名称，最后是许可证主机，值是组合发生的次数。

类似的东西：

dictionary['Feature1']['host1']['lichost1'] = 2
dictionary['Feature1']['host2']['lichost1'] = 1
dictionary['Feature2']['host1']['lichost2'] = 1

创建/更新这样一个字典的显而易见的方法是（假设我从CSV中逐行读取数据）：

for line in file:
    feature, machine, license = line.split(',')
    if feature not in dictionary:
        dictionary[feature] = {}
    if machine not in dictionary[feature]:
        dictionary[feature][machine] = {}
    if license not in dictionary[feature][machine]:
        dictionary[feature][machine][license] = 1
    else:
        dictionary[feature][machine][license] += 1

这可以确保我永远不会遇到任何级别的密钥未找到错误。

执行上述操作的最佳方法是什么（对于任意数量的嵌套级别）？

Answer 1

您可以使用defaultdict：

from collections import defaultdict
import csv

def d1(): return defaultdict(int)
def d2(): return defaultdict(d1)
def d3(): return defaultdict(d2)
dictionary = d3()

with open('input.csv') as input_file:
    next (input_file);
    for line in csv.reader(input_file):
        dictionary[line[0]][line[1]][line[2]] += 1

assert dictionary['Feature1']['host1']['lichost1'] == 2
assert dictionary['Feature1']['host2']['lichost1'] == 1
assert dictionary['Feature2']['host1']['lichost2'] == 1
assert dictionary['InvalidFeature']['host1']['lichost1'] == 0

如果多功能def打扰你，你可以更简洁地说同样的话：

dictionary = defaultdict(lambda: defaultdict(lambda: defaultdict(int)))

Pythonic在Python中更新嵌套字典的方法

1 个答案: