Customers Who Never Order — LeetCode 183 Python Solution

The problem

List the customers who have never placed a single order. Customers has id (int, primary key) and name (varchar); Orders has id (int, primary key) and customerId (int), which references a customer. Return the names in a column called Customers.

Example

Input

Customers(id, name) = (1, 'Ana'), (2, 'Ben'), (3, 'Cleo'), (4, 'Dev'); Orders(id, customerId) = (1, 3), (2, 1)

Output

Customers = 'Ben', 'Dev'

Explanation

Orders exist only for customers 1 and 3, so Ben and Dev never ordered.

Python solution

import pandas as pd


def find_customers(customers: pd.DataFrame, orders: pd.DataFrame) -> pd.DataFrame:
    # Select the customers whose 'id' is not present in the orders DataFrame's 'customerId' column.
    df = customers[~customers["id"].isin(orders["customerId"])]

    # Build a DataFrame that only contains the 'name' column and rename it as 'Customers'.
    df = df[["name"]].rename(columns={"name": "Customers"})

    return df

Complexity

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