Combine Two Tables — LeetCode 175 Python Solution

The problem

Report the first name, last name, city and state of every person on file, keeping people who have no address at all and returning a null city and state for them. Person holds personId (int, primary key), lastName (varchar) and firstName (varchar); Address holds addressId (int, primary key), personId (int, pointing at a person) plus city and state (varchar). The rows may be returned in any order.

Example

Input

Person(personId, lastName, firstName) = (1, 'Reyes', 'Carla'), (2, 'Nakamura', 'Dan'), (3, 'Osei', 'Ama'); Address(addressId, personId, city, state) = (1, 2, 'Austin', 'Texas'), (2, 3, 'Denver', 'Colorado')

Output

('Carla', 'Reyes', null, null), ('Dan', 'Nakamura', 'Austin', 'Texas'), ('Ama', 'Osei', 'Denver', 'Colorado')

Explanation

Carla has no matching address row, so the left join keeps her with a null city and state.

Python solution

import pandas as pd


def combine_two_tables(person: pd.DataFrame, address: pd.DataFrame) -> pd.DataFrame:
    return pd.merge(left=person, right=address, how="left", on="personId")[
        ["firstName", "lastName", "city", "state"]
    ]

Complexity

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