KWCHECKER a verifier and sanitizer for python kwargs parameters

also see explain-xkcd

(fun fact: email addresses can have a apostrophe in them - so that O'Connell will be happy, however that's not a problem, as the sign is allowed only in the first part of the address, and you can't have spaces in the address either. Still: better use sql prepared statements, to be on the safe side)

The kwchecker package simplifies validation & sanitation of python kwargs parameter, your can define most validations declaratively, in a map. See the following example, where the validator definitions are passed to the kwchecker.KwArgsChecker constructor.

        def func_to_test(**kwargs):
            checker = kwchecker.KwArgsChecker(required={
                    "first_name": (
                        str,
                        kwchecker.no_regex_validator("^\s*$", "Error: empty first name"),
                        kwchecker.strip_leading_trailing_space(),
                        kwchecker.capitalize_first_letter(),
                    ),
                    "last_name": (
                        str,
                        kwchecker.no_regex_validator(r"^\s*$", "Error: empty last name"),
                        kwchecker.strip_leading_trailing_space(),
                        kwchecker.capitalize_first_letter(),
                    ),

                    "title" : str,

                    "email" : kwchecker.email_validator(),

                    "phone" : (
                        kwchecker.regex_validator(r"^[0-9\+\-,\ \(\)#]*$", "not a vald phone number")
                        )
                }, opt={
                    "mood": kwchecker.int_range_validator(0, 10),
                    "plan": str
                })

            checker.validate(kwargs)

The constructor has two arguments required receives the definition for mandatory parameters passed via kwargs, opt receives definitions of optional parameters. An errror is triggered, if an actual parameter in kwargs does not appear in any of these definitions.] The constructor also has an optional sanitize_db parameter, if set to True then this will removes all ap ' and " characters.

Each allowed parameter name appears as a key in the dictionary arguments. The value of the entry defines the actual validation/sanitation. A type value will check, if the supplied argument is of the requested type

"title" : str - this will check if the kwargs parameter title is of type string.

A funcion value will be either a validation function, or a sanitier function.

"email" : kwchecker.email_validator() - this validates that the email parameter in kwargs is a valid email address. Note that function email_validator is being called here, as it returns a closure. Most of the verifiers can take additional arguments, like an error message that overrides the default one, therefore I kept with this convention for all validators and sanitizer functions, in order to make it consistent.

You may pass a tuple of values that are either types or functions. see

"last_name": (
    str,
    kwchecker.no_regex_validator(r"^\s*$", "Error: empty last name"),
    kwchecker.strip_leading_trailing_space(),
    kwchecker.capitalize_first_letter(),
)

The action for the kwargs last_name parameter will first verify that parameter to be of type string, then it will verify, that the value is not an empty string kwchecker.no_regex_validator(r"^\s*$", "Error: empty last name"), then it will strip the leading and trailing whitespaces kwchecker.strip_leading_trailing_space(), and capitalize the first letter of the value kwchecker.capitalize_first_letter()

validation/modifier action on all parameters

You can add actions on all parameters with the on_all_pre and on_all_post parameters. on_all_pre`` defines checks and validators that are run before any of the validators defined for any one of the parameters. on_all_post``` defines checks and validators that are run after any one of the validators defined for any one of the parameters.

Here is an example that users on_all_post, to strip leading and trailing spaces on all string values.

        def func_to_test(**kwargs):
            checker = kwchecker.KwArgsChecker(required={
                    "first_name": (
                        str,
                        kwchecker.no_regex_validator("^\s*$", "Error: empty first name"),
                    ),
                    "last_name": (
                        str,
                        kwchecker.no_regex_validator(r"^\s*$", "Error: empty last name"),
                                            ),

                    "title" : str,

                    "email" : kwchecker.email_validator(),

                    "phone" : (
                        kwchecker.regex_validator(r"^[0-9\+\-,\ \(\)#]*$", "not a vald phone number")
                        )
                },
                on_all_post = (kwchecker.strip_leading_trailing_space(), kwchecker.capitalize_first_letter()) 
            )

            checker.validate(kwargs)

Installation instructions

pip install kwchecker

Also see the project here kwchecker