In Python, find item in list of dicts, using bisect

The usual pattern here is similar to sorting by an attribute, decorate, operate, and undecorate. So in this case you'd just need to decorate and then call. However you'd want to avoid doing this since decorate would be O(n) whereas you want this to be O(logn). Therefore I'd consider your method best.

You could also use one of Python's many SortedDict implementations to manage your test_data. A sorted dict sorts the elements by key and maintains a mapping to a value. Some implementations also support a bisect operation on the keys. For example, the Python sortedcontainers module has a SortedDict that meets your requirements.

In your case it would look something like:

from sortedcontainers import SortedDict
offset_map = SortedDict((item['offset'], item['data']) for item in test_data)
index = offset_map.bisect(1275)
key = offset_map.iloc[index]
print offset_map[key]
# 120

The SortedDict type has a bisect function which returns the bisected index of the desired key. With that index, you can lookup the actual key. And with that key you can get the value.

All of these operations are very fast in sortedcontainers which is also conveniently implemented in pure-Python. There's a performance comparison too which discusses other choices and has benchmark data.