搜索词典列表以查看任何词典中是否存在键/值

Question

so I have a list of dictionaries, ex:

[{'title':'Green eggs and ham', 'author':'dr seuss'}, {'title':'matilda', 'author':'roald dahl'}]

What is the best way to search if outliers by malcolm gladwell exists in any of those dictionaries?

I was thinking of brute force checking each title and author, but I feel like there's gotta be a better way.

Answer 1

If you need all key-value pairs to match, you can just use in and have the list do the searching for you:

if {'title': 'outliers', 'author': 'malcolm gladwell'} in yourlist:

Otherwise, with no other indices, you'll have to 'manually' search the list. You can use the any function with a generator expression to make the test efficient enough (eg stop searching when a match is found), plus dictionary view objects to test for subsets of key-value pairs:

search = {'title': 'outliers', 'author': 'malcolm gladwell'}.viewitems()
if any(search <= d.viewitems() for d in yourlist):

would match even if dictionaries in yourlist have more keys than just title and author .

You can avoid full scans by using extra indices:

authors = {}
titles = {}
for d in yourlist:
    authors.set_default(d['author'], []).append(d)
    titles.set_default(d['title'], []).append(d)

creates extra mappings by specific keys in the dictionaries. No you can test for individual elements:

if any(d['title'] == 'outliers' for d in authors.get('malcolm gladwell', [])):

is a limited search just through all books by Malcolm Gladwell.

The titles and authors dictionaries map author and title strings to lists of the same dictionaries , shared with the yourlist list. However, adding or removing dictionaries from one such structure does require updating all structures. This is where a relational database comes in handy, as it is really good at keeping such indexes for you and will automatically keep these up-to-date.