Hanukkah of Data 5784 - Day 1 The Investigator

:: programming, python, puzzle

The Task

The task is to find the customer whose last name can be spelled by their phone number, using the letters shown for each number on a dial pad, and report their phone number. We’re given a customer file as follows:

>>> import pandas as pd
>>> df = pd.read_csv('noahs-customers.csv')
>>> df.loc[:5,'customerid':'phone']
   customerid                   name              address          citystatezip   birthdate         phone
0        1001     Jacqueline Alvarez    105N Elizabeth St   Manhattan, NY 10013  1958-01-23  315-377-5031
1        1002           Julie Howell      185-1 Linden St    Brooklyn, NY 11221  1956-12-03  680-537-8725
2        1003        Christopher Ali  174-28 Baisley Blvd     Jamaica, NY 11434  2001-09-20  315-846-6054
3        1004  Christopher Rodriguez    102 Mount Hope Pl       Bronx, NY 10453  1959-07-10  516-275-2292
4        1005      Jeffrey Wilkinson       17 St Marks Pl   Manhattan, NY 10003  1988-09-08  838-830-6960
5        1006             Emma Wells       86-34 102nd Rd  Ozone Park, NY 11416  1984-02-05  315-236-2043

Solution

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import re
import pandas as pd

letters = { '2' : 'abc', '3' : 'def', '4' : 'ghi', '5' : 'jkl',
            '6' : 'mno', '7' : 'pqrs', '8' : 'tuv', '9' : 'wxyz' }

def phone_matches_last_name(phone, name):
    phone     = re.sub(r'\D', '', phone)
    last_name = str.split(name)[-1].lower()

    if len(last_name) < len(phone):
        return False

    for d, c in zip(phone, last_name):
        if c not in letters.get(d, ''):
            return False

    return True

def solve():
    customers = pd.read_csv('noahs-customers.csv')
    predicate = lambda row: phone_matches_last_name(row['phone'], row['name'])

    return customers[customers.apply(predicate, axis=1)].iloc[0]['phone']

# ---------------------------------------------------------------------------------------------

assert solve() == '826-636-2286'

Commentary

Firstly, associate the numbers of a phone dial pad with its letters using a dict:

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letters = { '2' : 'abc', '3' : 'def', '4' : 'ghi', '5' : 'jkl',
            '6' : 'mno', '7' : 'pqrs', '8' : 'tuv', '9' : 'wxyz' }

Next, a helper predicate to indicate if a phone number can spell a name. We’ll clean the phone number by removing any non-numeric digits, and we grab the last name by splitting on space and taking the last element of the list. If the length of the last name is less than the length of the phone number, it’s not a match; otherwise, for each letter of the last name, see if it’s found in the list of letters associated with the phone number digit - if all are found, it’s a match.

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def phone_matches_last_name(phone, name):
    phone     = re.sub(r'\D', '', phone)
    last_name = str.split(name)[-1].lower()

    if len(last_name) < len(phone):
        return False

    for d, c in zip(phone, last_name):
        if c not in letters.get(d, ''):
            return False

    return True

With that in place, we just need to filter rows for which our predicate is true.

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def solve():
    customers = pd.read_csv('noahs-customers.csv')
    predicate = lambda row: phone_matches_last_name(row['phone'], row['name'])

    return customers[customers.apply(predicate, axis=1)].iloc[0]['phone']