迭代字典列表并附加python

Question

我有一个词典列表（a），并且我试图遍历词典搜索特定值，如果字典具有该值，则将该词典添加到新的词典集合中。 到目前为止，我有

newList = {}

a = [{"one": "green", "two" : "blue", "three" : "red"},
     {"two": "blue", "four" : "green", "five" : "yellow"},
     {"two": "blue", "six": "white", "seven" : "black"}]

for index in range(len(a)):
 if a[index][?] = ["blue"]:
   newList.append(a[index])

Answer 1

对于此用例/查询，您拥有的数据结构不太方便。 如果您不能更改数据结构，这是一个幼稚的解决方案：

newList = [d for d in a if "blue" in d.values()]

需要注意的是if "blue" in d.values()查找是O(n)这就是您应尽量避免在执行时in查找。

---

在这种情况下，更合适的数据结构是交换内部字典中的键和值的数据结构：

a = [{"green": "one", "blue": "two", "red": "three"},
     {"blue": "two":, "green": "four", "yellow": "five"},
     {"blue": "two", "white": "six", "black": "seven"}]

在这种情况下，您将按O(1)键查看字典：

newList = [d for d in a if "blue" in d]

Answer 2

我不确定您要尝试什么，但是为了达到您的目标，我尽可能少地修改了您的示例：

ewList = []
a = [{"one": "green", "two": "blue", "three": "red"},
     {"two": "blue", "four" : "green", "five" : "yellow"},
     {"two": "yellow", "six": "white", "seven" : "black"}]

for d in a:
    if "yellow" in d.values():
        ewList.append(d)

print ewList

输出：

[{'four': 'green', 'five': 'yellow', 'two': 'blue'}, {'seven': 'black', 'six': 'white', 'two': 'yellow'}]