extract.py

def extract(query):
    """extract takes in a `query` API function (which returns the first 5 usernames, lexicographically sorted,
    that start with a prefix) and returns the sorted list of all usernames in the database.

    For example, the `query` function in provided in `main` works as follows:
    
    query("a") #=> ["abracadara", "al", "alice", "alicia", "allen"]
    query("ab") #=> ["abracadara"]

    The following implementation would pass the assertion in `main`, but is not a correct solution since it
    works only for that example `query`:

    def extract(query):
        return query("ab") + query("al") + query("altercation") + query("b") + query("el") + query("ev") + query("m")

    Your goal is to write an `extract` method that is correct for any provided `query`.
    """
    # YOUR CODE HERE
    return [...]

def main():
    """Runs your solution -- no need to update (except to maybe try out different databases)."""
    # Sample implementation of the autocomplete API
    database = ["abracadara", "al", "alice", "alicia", "allen", "alter", "altercation", "bob", "element", "ello", "eve", "evening", "event", "eventually", "mallory"]
    query = lambda prefix: [d for d in database if d.startswith(prefix)][:5]
    assert extract(query) == database

main()