比较列表中嵌套字典的最佳方法，Python

Question

我正在查询公共端点以获取不同交易所的汇率，该汇率返回带有嵌套字典的列表。我最感兴趣的是嵌套字典中的关键“金额”字段。我正在努力想出一个解决方案来存储变量中具有最多“金额”值的嵌套字典。任何想法都会非常有帮助。我正在用头撞墙。

这是列表：

list_with_nested_dicts = [{"partner":"simpleswap","amount":0,"currency":"cel","supportRate":3,"duration":0,"fixed":true,"min":0,"max":0,"exists":false,"id":""},{"partner":"simpleswap","amount":0,"currency":"cel","supportRate":3,"duration":0,"fixed":false,"min":0,"max":0,"exists":false,"id":""},{"partner":"stealthex","amount":37.90346104,"currency":"cel","supportRate":2,"duration":66.62083333333334,"fixed":true,"min":39.91443225,"max":2550.215226,"exists":true,"id":""},{"partner":"stealthex","amount":37.20972396,"currency":"cel","supportRate":2,"duration":23.158333333333335,"fixed":false,"min":77.82938688,"max":25209.49720665,"exists":true,"id":""},{"partner":"godex","amount":0,"currency":"cel","supportRate":0,"duration":0,"fixed":true,"min":0,"max":0,"exists":false,"id":""},{"partner":"changenow","amount":37.2077365,"currency":"cel","supportRate":2,"duration":11.08859649122807,"fixed":false,"min":56.60646516,"max":25259.88795509,"exists":true,"id":""},{"partner":"changelly","amount":0,"currency":"cel","supportRate":1,"duration":0,"fixed":true,"min":0,"max":0,"exists":false,"id":""},{"partner":"changelly","amount":0,"currency":"cel","supportRate":1,"duration":0,"fixed":false,"min":0,"max":0,"exists":false,"id":""},{"partner":"instaswap","amount":0,"currency":"cel","supportRate":2,"duration":0,"fixed":false,"min":0,"max":0,"exists":false,"id":""},{"partner":"exolix","amount":0,"currency":"cel","supportRate":0,"duration":0,"fixed":true,"min":0,"max":0,"exists":false,"id":""},{"partner":"fixedfloat","amount":0,"currency":"cel","supportRate":3,"duration":0,"fixed":false,"min":0,"max":0,"exists":false,"id":""},{"partner":"switchain","amount":0,"currency":"cel","supportRate":2,"duration":0,"fixed":true,"min":0,"max":0,"exists":false,"id":""},{"partner":"changehero","amount":0,"currency":"cel","supportRate":3,"duration":56.41111111111111,"fixed":true,"min":0,"max":0,"exists":false,"id":""},{"partner":"changehero","amount":0,"currency":"cel","supportRate":3,"duration":2.4833333333333334,"fixed":false,"min":0,"max":0,"exists":false,"id":""},{"partner":"binance","amount":0,"currency":"cel","supportRate":2,"duration":0,"fixed":false,"min":0,"max":0,"exists":false,"id":""},{"partner":"nexchange","amount":0,"currency":"cel","supportRate":3,"duration":0,"fixed":true,"min":0,"max":0,"exists":false,"id":""},{"partner":"letsexchange","amount":0,"currency":"cel","supportRate":2,"duration":0,"fixed":true,"min":0,"max":0,"exists":false,"id":""},{"partner":"letsexchange","amount":0,"currency":"cel","supportRate":2,"duration":0,"fixed":false,"min":0,"max":0,"exists":false,"id":""},{"partner":"alfacash","amount":0,"currency":"cel","supportRate":3,"duration":0,"fixed":true,"min":0,"max":0,"exists":false,"id":""}]

数量最多的词典是：

{"partner":"stealthex","amount":37.90346104,"currency":"cel","supportRate":2,"duration":66.62083333333334,"fixed":true,"min":39.91443225,"max":2550.215226,"exists":true,"id":""}

Answer 1

使用key参数max：

from operator import  itemgetter
res = max(list_with_nested_dicts, key=itemgetter("amount"))
print(res)

输出

{'partner': 'stealthex', 'amount': 37.90346104, 'currency': 'cel', 'supportRate': 2, 'duration': 66.62083333333334, 'fixed': True, 'min': 39.91443225, 'max': 2550.215226, 'exists': True, 'id': ''}

从文档中：

key 参数指定一个单参数排序函数，类似于 list.sort() 所使用的函数

请注意，无需使用operator.itemgetter，您可以简单地使用 lambda 函数作为 的值key：

max(list_with_nested_dicts, key=lambda x: x["amount"])

另外，如果某些词典没有 item "amount"，我建议您使用.get如下：

default = 0
res = max(list_with_nested_dicts, key=lambda x: x.get("amount", default))

其中default应该是最适合您需求的值。