Python: List vs Dict for look up table

Question

I have about 10million values that I need to put in some type of look up table, so I was wondering which would be more efficient a list or dict?

I know

Answer 1

You want a dict.

For (unsorted) lists in Python, the "in" operation requires O(n) time---not good when you have a large amount of data. A dict, on the other hand, is a hash table, so you can expect O(1) lookup time.

As others have noted, you might choose a set (a special type of dict) instead, if you only have keys rather than key/value pairs.

Related:

• Python wiki: information on the time complexity of Python container operations.
• SO: Python container operation time and memory complexities