Function validate_email_local_part

email_validator/syntax.py:231–389

Validates the syntax of the local part of an email address.

(local: str, allow_smtputf8: bool = True, allow_empty_local: bool = False,
                              quoted_local_part: bool = False, strict: bool = False)

def validate_email_local_part(local: str, allow_smtputf8: bool = True, allow_empty_local: bool = False,
                              quoted_local_part: bool = False, strict: bool = False) -> LocalPartValidationResult:
    """Validates the syntax of the local part of an email address."""

    if len(local) == 0:
        if not allow_empty_local:
            raise EmailSyntaxError("There must be something before the @-sign.")

        # The caller allows an empty local part. Useful for validating certain
        # Postfix aliases.
        return {
            "local_part": local,
            "ascii_local_part": local,
            "smtputf8": False,
        }

    # Check the length of the local part by counting characters.
    # (RFC 5321 4.5.3.1.1)
    # We're checking the number of characters here. If the local part
    # is ASCII-only, then that's the same as bytes (octets). If it's
    # internationalized, then the UTF-8 encoding may be longer, but
    # that may not be relevant. We will check the total address length
    # instead.
    if strict and len(local) > LOCAL_PART_MAX_LENGTH:
        reason = get_length_reason(local, limit=LOCAL_PART_MAX_LENGTH)
        raise EmailSyntaxError(f"The email address is too long before the @-sign {reason}.")

    # Check the local part against the non-internationalized regular expression.
    # Most email addresses match this regex so it's probably fastest to check this first.
    # (RFC 5322 3.2.3)
    # All local parts matching the dot-atom rule are also valid as a quoted string
    # so if it was originally quoted (quoted_local_part is True) and this regex matches,
    # it's ok.
    # (RFC 5321 4.1.2 / RFC 5322 3.2.4).
    if DOT_ATOM_TEXT.match(local):
        # It's valid. And since it's just the permitted ASCII characters,
        # it's normalized and safe. If the local part was originally quoted,
        # the quoting was unnecessary and it'll be returned as normalized to
        # non-quoted form.

        # Return the local part and flag that SMTPUTF8 is not needed.
        return {
            "local_part": local,
            "ascii_local_part": local,
            "smtputf8": False,
        }

    # The local part failed the basic dot-atom check. Try the extended character set
    # for internationalized addresses. It's the same pattern but with additional
    # characters permitted.
    # RFC 6531 section 3.3.
    valid: Optional[str] = None
    requires_smtputf8 = False
    if DOT_ATOM_TEXT_INTL.match(local):
        # But international characters in the local part may not be permitted.
        if not allow_smtputf8:
            # Check for invalid characters against the non-internationalized
            # permitted character set.