Python:使用另一个大型词典更新大型词典 [英] Python: updating a large dictionary using another large dictionary

问题描述

我正在尝试使用另一个词典中具有相似键(相同日期但格式不同)的值来更新大型词典的某些值.我当前正在使用的进程太慢，我想减少瓶颈.

I am trying to update some values of a large dictionary using values from another dictionary where they have similar keys (the same date but in a different format). The process I'm currently using is too slow and I want to reduce the bottleneck.

这是我当前的解决方案(它将更新后的字典写到文件中):

This is my current solution (it writes the updated dict to a file):

from dateutil import parser
File = open(r'E:Test1.txt','w')

b = {'1946-1-1':0,..........,'2012-12-31':5}
d = {'1952-12-12':5,........,'1994-7-2':10}

for key1, val1 in b.items():
    DateK1 = parser.parse(key1)
    Value = val1
    for key2, val2 in d.items():
        DateK2 = parser.parse(key2)
        if DateK1 == DateK2:
            d[key2] = Value        

Order= sorted(d.items(), key=lambda t: t[0])

for item in Order:
    File.write('%s,%s\n' % item)
File.close()

推荐答案

您应使用 update 合并字典的方法:

You should use the update method to merge dictionaries:

b.update(d)

.

此刻，您正在为b中的每个键遍历d ...，这很慢.您可以通过设置两个具有匹配键的字典来解决此问题(相等的日期将对相同的哈希进行散列-也许这里要注意的很酷的事情是日期时间对象散列):

At the moment you are iterating over d for every key in b... which is slow. You can get around this by setting up two dictionaries which will have matching keys (and equal dates will hash the same - perhaps the cool thing to note here is that datetime objects hash):

b1 = dict( (parser.parse(k),v) for k,v for b.iteritems() )
d1 = dict( (parser.parse(k),v) for k,v for d.iteritems() )

d1.update(b1) # update d1 with the values from b1

我刚刚意识到，您并没有相当进行更新，因为仅更新了那些共享值，所以(同样，只需重复一次):

I've just realised that you're not quite doing an update, since only those shared values are being updated, so instead (again by just iterating once):

for k_d1 in d1:
    if k_d1 in b1:
        d1[k_d1] = b1[k_d1]

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