RegExp validation for password explained
r'^ (?=.*[A-Z]) // should contain at least one upper case (?=.*[a-z]) // should contain at least one lower case (?=.*?[0-9]) // should contain at least one digit (?=.*?[!@#\$&*~]) // should contain at least one Special character .{8,} // Must be at least 8 characters in length $