python - 通过定义排序顺序，根据子字典键对 python 字典键进行排序

Question

我的问题是对 another question 的扩展其中 OP 有一本字典，即下面的字典，并希望根据子字典键对主键进行排序

myDict = {
    'SER12346': {'serial_num': 'SER12346', 'site_location': 'North America'},
    'ABC12345': {'serial_num': 'ABC12345', 'site_location': 'South America'},
    'SER12345': {'serial_num': 'SER12345', 'site_location': 'North America'},
    'SER12347': {'serial_num': 'SER12347', 'site_location': 'South America'},
    'ABC12346': {'serial_num': 'ABC12346', 'site_location': 'Europe'}
}

提议的(在下面引用的)解决方案非常有效。

dicts = myDict.items()
dicts.sort(key=lambda (k,d): (d['site_location'], d['serial_num'],))

但是，此解决方案对所有内容都按升序排序(按降序排序很简单)。我想知道是否可以定义排序顺序的混合，比如 serial_num 升序但 site_location 降序？

Answer 1

这是一个可能的解决方案，因为列表排序是 stable .我稍微更改了数据以证明它有效。

此方法在Python documentation中也有规定。 .

myDict = {
    'SER12346': {'serial_num': 'SER12346', 'site_location': 'North America'},
    'ABC12346': {'serial_num': 'ABC12345', 'site_location': 'Europe'},
    'ABC12345': {'serial_num': 'ABC12345', 'site_location': 'South America'},
    'SER12345': {'serial_num': 'SER12345', 'site_location': 'North America'},
    'SER12347': {'serial_num': 'SER12347', 'site_location': 'South America'}
}

result = sorted(myDict.items(), key=lambda x: x[1]['site_location'], reverse=True)
result = sorted(result, key=lambda x: x[1]['serial_num'])

# [('ABC12345', {'serial_num': 'ABC12345', 'site_location': 'South America'}),
#  ('ABC12346', {'serial_num': 'ABC12345', 'site_location': 'Europe'}),
#  ('SER12345', {'serial_num': 'SER12345', 'site_location': 'North America'}),
#  ('SER12346', {'serial_num': 'SER12346', 'site_location': 'North America'}),
#  ('SER12347', {'serial_num': 'SER12347', 'site_location': 'South America'})]