当找不到给定的字典键时，尝试包含一个空值

Question

我有一个设备软件列表，我正试图制作一个字典，其中键是软件的名称，并将所有版本的数组都值给这个键。

设备软件列表格式

[
    [
        {"name": "openjdk-8-jre", "version": "8u171-b11-1~deb9u1"},
        {"name": "python2.7", "version": "2.7.13"},
        {"name": "npm", "version": "8.0.0"},
    ],
    [
        {"name": "openjdk-8-jre", "version": "8u171-b11-1~deb9u1"},
    ],
    [
        {"name": "python2.7", "version": "2.7.13"},
        {"name": "npm", "version": "7.0.0"},
    ],
]

我想做的是：

softwares = {}

for software in all_equipment_softwares:
    softwares[software] = []

for equipment in equipments_dump:
    for software in equipment["softwares"]:
        software_name = software["name"]
        software_version = software["version"]

        softwares[software_name].append(software_version)

我得到的是：

[
    {"openjdk-8-jre": ["8u171-b11-1~deb9u1", "8u171-b11-1~deb9u1"]},
    {"python2.7": ["2.7.13", "2.7.13"]},
    {"npm": ["8.0.0", "7.0.0"]},
]

我已经想了好几个小时了，但我无法得到预期的结果

预期结果：

[
    {"openjdk-8-jre": ["8u171-b11-1~deb9u1", "8u171-b11-1~deb9u1", None]},
    {"python2.7": ["2.7.13", None, "2.7.13"]},
    {"npm": ["8.0.0", None, "7.0.0"]},
]

当软件不在该设备上时，我如何在给定密钥的值中添加空值？

Answer 1

这里有一种方法，您可以使用单一字典来获得输出，而不是字典列表。关键的洞察力是将值预先填充为None列表。请随时提出任何澄清性的问题。

softwares = {}
softwares_length = len(all_equipment_softwares)

#iterate through each software_list of all_equipment_softwares
for count, software_list in enumerate(all_equipment_softwares):

    #iterate through each software of software_list
    for software in software_list:

        #if it's a software we haven't seen add it to our dictionary with an array full of None based on the length of all_equipment_softwares
        if software['name'] not in softwares:
            softwares[software['name']] = [None] * softwares_length

        #update the dictionary value (the list) from None to the software version
        softwares[software['name']][count] = software['version']
print(software)

输出

{'openjdk-8-jre': ['8u171-b11-1~deb9u1', '8u171-b11-1~deb9u1', None],
'python2.7': ['2.7.13', None, '2.7.13'],
'npm': ['8.0.0', None, '7.0.0']}

Answer 2

software\_version = software["version"]

你的问题有点含糊。当软件不存在于该设备上时，我假设上面的KeyError会发生爆炸。

使用：

    software_version = software.get("version")

另外，请广播电台：https://docs.python.org/3/library/stdtypes.html#dict.get