--description--

On October 29, 1971, the first email ever was sent, introducing the username@domain format we still use. Now, there are billions of email addresses.

In this challenge, you are given a list of email addresses and need to sort them alphabetically by domain name first (the part after the @), and username second (the part before the @).

• Sorting should be case-insensitive.
• If more than one email has the same domain, sort them by their username.
• Return an array of the sorted addresses.
• Returned addresses should retain their original case.

For example, given ["[email protected]", "[email protected]", "[email protected]"], return ["[email protected]", "[email protected]", "[email protected]"].

--hints--

sort(["[email protected]", "[email protected]", "[email protected]"]) should return ["[email protected]", "[email protected]", "[email protected]"].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(sort(["[email protected]", "[email protected]", "[email protected]"]), ["[email protected]", "[email protected]", "[email protected]"])`)
}})

sort(["[email protected]", "[email protected]", "[email protected]"]) should return ["[email protected]", "[email protected]", "[email protected]"].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(sort(["[email protected]", "[email protected]", "[email protected]"]), ["[email protected]", "[email protected]", "[email protected]"])`)
}})

sort(["[email protected]", "[email protected]", "[email protected]"]) should return ["[email protected]", "[email protected]", "[email protected]"].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(sort(["[email protected]", "[email protected]", "[email protected]"]), ["[email protected]", "[email protected]", "[email protected]"])`)
}})

sort(["[email protected]", "[email protected]", "[email protected]"]) should return ["[email protected]", "[email protected]", "[email protected]"].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(sort(["[email protected]", "[email protected]", "[email protected]"]), ["[email protected]", "[email protected]", "[email protected]"])`)
}})

sort(["[email protected]", "[email protected]", "[email protected]", "[email protected]", "[email protected]", "[email protected]"]) should return ["[email protected]", "[email protected]", "[email protected]", "[email protected]", "[email protected]", "[email protected]"].

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(sort(["[email protected]", "[email protected]", "[email protected]", "[email protected]", "[email protected]", "[email protected]"]), ["[email protected]", "[email protected]", "[email protected]", "[email protected]", "[email protected]", "[email protected]"])`)
}})

--seed--

--seed-contents--

def sort(emails):

    return emails

--solutions--

def sort(emails):
    return sorted(
        emails,
        key=lambda email: (email.split('@')[1].lower(), email.split('@')[0].lower())
    )