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Challenge 67: Email Validator

curriculum/challenges/english/blocks/daily-coding-challenges-python/68cae5b538ff798bbd4da005.md

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--description--

Given a string, determine if it is a valid email address using the following constraints:

  • It must contain exactly one @ symbol.
  • The local part (before the @):
    • Can only contain letters (a-z, A-Z), digits (0-9), dots (.), underscores (_), or hyphens (-).
    • Cannot start or end with a dot.
  • The domain part (after the @):
    • Must contain at least one dot.
    • Must end with a dot followed by at least two letters.
  • Neither the local or domain part can have two dots in a row.

--hints--

validate("[email protected]") should return True.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(validate("[email protected]"), True)`)
}})

validate("[email protected]") should return True.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(validate("[email protected]"), True)`)
}})

validate("[email protected]") should return False.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(validate("[email protected]"), False)`)
}})

validate("[email protected]") should return False.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(validate("[email protected]"), False)`)
}})

validate("freecodecamp.org") should return False.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(validate("freecodecamp.org"), False)`)
}})

validate("develop.ment_user@c0D!NG.R.CKS") should return True.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(validate("develop.ment_user@c0D!NG.R.CKS"), True)`)
}})

validate("[email protected]") should return False.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(validate("[email protected]"), False)`)
}})

validate("[email protected]") should return False.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(validate("[email protected]"), False)`)
}})

validate("develop..ment_user@c0D!NG.R.CKS") should return False.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(validate("develop..ment_user@c0D!NG.R.CKS"), False)`)
}})

validate("git@[email protected]") should return False.

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertIs(validate("git@[email protected]"), False)`)
}})

--seed--

--seed-contents--

py
def validate(email):

    return email

--solutions--

py
import re
def validate(email):
    if '..' in email:
        return False

    parts = email.split('@')
    if len(parts) != 2:
        return False

    local, domain = parts

    if local.startswith('.') or local.endswith('.'):
        return False
    if not re.match(r'^[a-zA-Z0-9._-]+$', local):
        return False

    if '.' not in domain:
        return False

    tld = domain.split('.')[-1]
    if len(tld) < 2 or not tld.isalpha():
        return False

    return True