Metadata-Version: 2.1 Name: voluptuous Version: 0.11.5 Summary: # Voluptuous is a Python data validation library Home-page: https://github.com/alecthomas/voluptuous Author: Alec Thomas Author-email: alec@swapoff.org License: BSD Download-URL: https://pypi.python.org/pypi/voluptuous Platform: any Classifier: Development Status :: 5 - Production/Stable Classifier: Intended Audience :: Developers Classifier: License :: OSI Approved :: BSD License Classifier: Operating System :: OS Independent Classifier: Programming Language :: Python :: 2 Classifier: Programming Language :: Python :: 2.7 Classifier: Programming Language :: Python :: 3 Classifier: Programming Language :: Python :: 3.6 Classifier: Programming Language :: Python :: 3.7 Description-Content-Type: text/markdown # Voluptuous is a Python data validation library [![Build Status](https://travis-ci.org/alecthomas/voluptuous.png)](https://travis-ci.org/alecthomas/voluptuous) [![Coverage Status](https://coveralls.io/repos/github/alecthomas/voluptuous/badge.svg?branch=master)](https://coveralls.io/github/alecthomas/voluptuous?branch=master) [![Gitter chat](https://badges.gitter.im/alecthomas.png)](https://gitter.im/alecthomas/Lobby) Voluptuous, *despite* the name, is a Python data validation library. It is primarily intended for validating data coming into Python as JSON, YAML, etc. It has three goals: 1. Simplicity. 2. Support for complex data structures. 3. Provide useful error messages. ## Contact Voluptuous now has a mailing list! Send a mail to [](mailto:voluptuous@librelist.com) to subscribe. Instructions will follow. You can also contact me directly via [email](mailto:alec@swapoff.org) or [Twitter](https://twitter.com/alecthomas). To file a bug, create a [new issue](https://github.com/alecthomas/voluptuous/issues/new) on GitHub with a short example of how to replicate the issue. ## Documentation The documentation is provided [here](http://alecthomas.github.io/voluptuous/). ## Changelog See [CHANGELOG.md](https://github.com/alecthomas/voluptuous/blob/master/CHANGELOG.md). ## Show me an example Twitter's [user search API](https://dev.twitter.com/rest/reference/get/users/search) accepts query URLs like: ``` $ curl 'https://api.twitter.com/1.1/users/search.json?q=python&per_page=20&page=1' ``` To validate this we might use a schema like: ```pycon >>> from voluptuous import Schema >>> schema = Schema({ ... 'q': str, ... 'per_page': int, ... 'page': int, ... }) ``` This schema very succinctly and roughly describes the data required by the API, and will work fine. But it has a few problems. Firstly, it doesn't fully express the constraints of the API. According to the API, `per_page` should be restricted to at most 20, defaulting to 5, for example. To describe the semantics of the API more accurately, our schema will need to be more thoroughly defined: ```pycon >>> from voluptuous import Required, All, Length, Range >>> schema = Schema({ ... Required('q'): All(str, Length(min=1)), ... Required('per_page', default=5): All(int, Range(min=1, max=20)), ... 'page': All(int, Range(min=0)), ... }) ``` This schema fully enforces the interface defined in Twitter's documentation, and goes a little further for completeness. "q" is required: ```pycon >>> from voluptuous import MultipleInvalid, Invalid >>> try: ... schema({}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "required key not provided @ data['q']" True ``` ...must be a string: ```pycon >>> try: ... schema({'q': 123}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "expected str for dictionary value @ data['q']" True ``` ...and must be at least one character in length: ```pycon >>> try: ... schema({'q': ''}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "length of value must be at least 1 for dictionary value @ data['q']" True >>> schema({'q': '#topic'}) == {'q': '#topic', 'per_page': 5} True ``` "per\_page" is a positive integer no greater than 20: ```pycon >>> try: ... schema({'q': '#topic', 'per_page': 900}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "value must be at most 20 for dictionary value @ data['per_page']" True >>> try: ... schema({'q': '#topic', 'per_page': -10}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "value must be at least 1 for dictionary value @ data['per_page']" True ``` "page" is an integer \>= 0: ```pycon >>> try: ... schema({'q': '#topic', 'per_page': 'one'}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) "expected int for dictionary value @ data['per_page']" >>> schema({'q': '#topic', 'page': 1}) == {'q': '#topic', 'page': 1, 'per_page': 5} True ``` ## Defining schemas Schemas are nested data structures consisting of dictionaries, lists, scalars and *validators*. Each node in the input schema is pattern matched against corresponding nodes in the input data. ### Literals Literals in the schema are matched using normal equality checks: ```pycon >>> schema = Schema(1) >>> schema(1) 1 >>> schema = Schema('a string') >>> schema('a string') 'a string' ``` ### Types Types in the schema are matched by checking if the corresponding value is an instance of the type: ```pycon >>> schema = Schema(int) >>> schema(1) 1 >>> try: ... schema('one') ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "expected int" True ``` ### URL's URL's in the schema are matched by using `urlparse` library. ```pycon >>> from voluptuous import Url >>> schema = Schema(Url()) >>> schema('http://w3.org') 'http://w3.org' >>> try: ... schema('one') ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "expected a URL" True ``` ### Lists Lists in the schema are treated as a set of valid values. Each element in the schema list is compared to each value in the input data: ```pycon >>> schema = Schema([1, 'a', 'string']) >>> schema([1]) [1] >>> schema([1, 1, 1]) [1, 1, 1] >>> schema(['a', 1, 'string', 1, 'string']) ['a', 1, 'string', 1, 'string'] ``` However, an empty list (`[]`) is treated as is. If you want to specify a list that can contain anything, specify it as `list`: ```pycon >>> schema = Schema([]) >>> try: ... schema([1]) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "not a valid value @ data[1]" True >>> schema([]) [] >>> schema = Schema(list) >>> schema([]) [] >>> schema([1, 2]) [1, 2] ``` ### Sets and frozensets Sets and frozensets are treated as a set of valid values. Each element in the schema set is compared to each value in the input data: ```pycon >>> schema = Schema({42}) >>> schema({42}) == {42} True >>> try: ... schema({43}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "invalid value in set" True >>> schema = Schema({int}) >>> schema({1, 2, 3}) == {1, 2, 3} True >>> schema = Schema({int, str}) >>> schema({1, 2, 'abc'}) == {1, 2, 'abc'} True >>> schema = Schema(frozenset([int])) >>> try: ... schema({3}) ... raise AssertionError('Invalid not raised') ... except Invalid as e: ... exc = e >>> str(exc) == 'expected a frozenset' True ``` However, an empty set (`set()`) is treated as is. If you want to specify a set that can contain anything, specify it as `set`: ```pycon >>> schema = Schema(set()) >>> try: ... schema({1}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "invalid value in set" True >>> schema(set()) == set() True >>> schema = Schema(set) >>> schema({1, 2}) == {1, 2} True ``` ### Validation functions Validators are simple callables that raise an `Invalid` exception when they encounter invalid data. The criteria for determining validity is entirely up to the implementation; it may check that a value is a valid username with `pwd.getpwnam()`, it may check that a value is of a specific type, and so on. The simplest kind of validator is a Python function that raises ValueError when its argument is invalid. Conveniently, many builtin Python functions have this property. Here's an example of a date validator: ```pycon >>> from datetime import datetime >>> def Date(fmt='%Y-%m-%d'): ... return lambda v: datetime.strptime(v, fmt) ``` ```pycon >>> schema = Schema(Date()) >>> schema('2013-03-03') datetime.datetime(2013, 3, 3, 0, 0) >>> try: ... schema('2013-03') ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "not a valid value" True ``` In addition to simply determining if a value is valid, validators may mutate the value into a valid form. An example of this is the `Coerce(type)` function, which returns a function that coerces its argument to the given type: ```python def Coerce(type, msg=None): """Coerce a value to a type. If the type constructor throws a ValueError, the value will be marked as Invalid. """ def f(v): try: return type(v) except ValueError: raise Invalid(msg or ('expected %s' % type.__name__)) return f ``` This example also shows a common idiom where an optional human-readable message can be provided. This can vastly improve the usefulness of the resulting error messages. ### Dictionaries Each key-value pair in a schema dictionary is validated against each key-value pair in the corresponding data dictionary: ```pycon >>> schema = Schema({1: 'one', 2: 'two'}) >>> schema({1: 'one'}) {1: 'one'} ``` #### Extra dictionary keys By default any additional keys in the data, not in the schema will trigger exceptions: ```pycon >>> schema = Schema({2: 3}) >>> try: ... schema({1: 2, 2: 3}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "extra keys not allowed @ data[1]" True ``` This behaviour can be altered on a per-schema basis. To allow additional keys use `Schema(..., extra=ALLOW_EXTRA)`: ```pycon >>> from voluptuous import ALLOW_EXTRA >>> schema = Schema({2: 3}, extra=ALLOW_EXTRA) >>> schema({1: 2, 2: 3}) {1: 2, 2: 3} ``` To remove additional keys use `Schema(..., extra=REMOVE_EXTRA)`: ```pycon >>> from voluptuous import REMOVE_EXTRA >>> schema = Schema({2: 3}, extra=REMOVE_EXTRA) >>> schema({1: 2, 2: 3}) {2: 3} ``` It can also be overridden per-dictionary by using the catch-all marker token `extra` as a key: ```pycon >>> from voluptuous import Extra >>> schema = Schema({1: {Extra: object}}) >>> schema({1: {'foo': 'bar'}}) {1: {'foo': 'bar'}} ``` #### Required dictionary keys By default, keys in the schema are not required to be in the data: ```pycon >>> schema = Schema({1: 2, 3: 4}) >>> schema({3: 4}) {3: 4} ``` Similarly to how extra\_ keys work, this behaviour can be overridden per-schema: ```pycon >>> schema = Schema({1: 2, 3: 4}, required=True) >>> try: ... schema({3: 4}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "required key not provided @ data[1]" True ``` And per-key, with the marker token `Required(key)`: ```pycon >>> schema = Schema({Required(1): 2, 3: 4}) >>> try: ... schema({3: 4}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "required key not provided @ data[1]" True >>> schema({1: 2}) {1: 2} ``` #### Optional dictionary keys If a schema has `required=True`, keys may be individually marked as optional using the marker token `Optional(key)`: ```pycon >>> from voluptuous import Optional >>> schema = Schema({1: 2, Optional(3): 4}, required=True) >>> try: ... schema({}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "required key not provided @ data[1]" True >>> schema({1: 2}) {1: 2} >>> try: ... schema({1: 2, 4: 5}) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "extra keys not allowed @ data[4]" True ``` ```pycon >>> schema({1: 2, 3: 4}) {1: 2, 3: 4} ``` ### Recursive / nested schema You can use `voluptuous.Self` to define a nested schema: ```pycon >>> from voluptuous import Schema, Self >>> recursive = Schema({"more": Self, "value": int}) >>> recursive({"more": {"value": 42}, "value": 41}) == {'more': {'value': 42}, 'value': 41} True ``` ### Extending an existing Schema Often it comes handy to have a base `Schema` that is extended with more requirements. In that case you can use `Schema.extend` to create a new `Schema`: ```pycon >>> from voluptuous import Schema >>> person = Schema({'name': str}) >>> person_with_age = person.extend({'age': int}) >>> sorted(list(person_with_age.schema.keys())) ['age', 'name'] ``` The original `Schema` remains unchanged. ### Objects Each key-value pair in a schema dictionary is validated against each attribute-value pair in the corresponding object: ```pycon >>> from voluptuous import Object >>> class Structure(object): ... def __init__(self, q=None): ... self.q = q ... def __repr__(self): ... return ''.format(self) ... >>> schema = Schema(Object({'q': 'one'}, cls=Structure)) >>> schema(Structure(q='one')) ``` ### Allow None values To allow value to be None as well, use Any: ```pycon >>> from voluptuous import Any >>> schema = Schema(Any(None, int)) >>> schema(None) >>> schema(5) 5 ``` ## Error reporting Validators must throw an `Invalid` exception if invalid data is passed to them. All other exceptions are treated as errors in the validator and will not be caught. Each `Invalid` exception has an associated `path` attribute representing the path in the data structure to our currently validating value, as well as an `error_message` attribute that contains the message of the original exception. This is especially useful when you want to catch `Invalid` exceptions and give some feedback to the user, for instance in the context of an HTTP API. ```pycon >>> def validate_email(email): ... """Validate email.""" ... if not "@" in email: ... raise Invalid("This email is invalid.") ... return email >>> schema = Schema({"email": validate_email}) >>> exc = None >>> try: ... schema({"email": "whatever"}) ... except MultipleInvalid as e: ... exc = e >>> str(exc) "This email is invalid. for dictionary value @ data['email']" >>> exc.path ['email'] >>> exc.msg 'This email is invalid.' >>> exc.error_message 'This email is invalid.' ``` The `path` attribute is used during error reporting, but also during matching to determine whether an error should be reported to the user or if the next match should be attempted. This is determined by comparing the depth of the path where the check is, to the depth of the path where the error occurred. If the error is more than one level deeper, it is reported. The upshot of this is that *matching is depth-first and fail-fast*. To illustrate this, here is an example schema: ```pycon >>> schema = Schema([[2, 3], 6]) ``` Each value in the top-level list is matched depth-first in-order. Given input data of `[[6]]`, the inner list will match the first element of the schema, but the literal `6` will not match any of the elements of that list. This error will be reported back to the user immediately. No backtracking is attempted: ```pycon >>> try: ... schema([[6]]) ... raise AssertionError('MultipleInvalid not raised') ... except MultipleInvalid as e: ... exc = e >>> str(exc) == "not a valid value @ data[0][0]" True ``` If we pass the data `[6]`, the `6` is not a list type and so will not recurse into the first element of the schema. Matching will continue on to the second element in the schema, and succeed: ```pycon >>> schema([6]) [6] ``` ## Multi-field validation Validation rules that involve multiple fields can be implemented as custom validators. It's recommended to use `All()` to do a two-pass validation - the first pass checking the basic structure of the data, and only after that, the second pass applying your cross-field validator: ```python def passwords_must_match(passwords): if passwords['password'] != passwords['password_again']: raise Invalid('passwords must match') return passwords s=Schema(All( # First "pass" for field types {'password':str, 'password_again':str}, # Follow up the first "pass" with your multi-field rules passwords_must_match )) # valid s({'password':'123', 'password_again':'123'}) # raises MultipleInvalid: passwords must match s({'password':'123', 'password_again':'and now for something completely different'}) ``` With this structure, your multi-field validator will run with pre-validated data from the first "pass" and so will not have to do its own type checking on its inputs. The flipside is that if the first "pass" of validation fails, your cross-field validator will not run: ``` # raises Invalid because password_again is not a string # passwords_must_match() will not run because first-pass validation already failed s({'password':'123', 'password_again': 1337}) ``` ## Running tests. Voluptuous is using nosetests: $ nosetests ## Why use Voluptuous over another validation library? **Validators are simple callables** : No need to subclass anything, just use a function. **Errors are simple exceptions.** : A validator can just `raise Invalid(msg)` and expect the user to get useful messages. **Schemas are basic Python data structures.** : Should your data be a dictionary of integer keys to strings? `{int: str}` does what you expect. List of integers, floats or strings? `[int, float, str]`. **Designed from the ground up for validating more than just forms.** : Nested data structures are treated in the same way as any other type. Need a list of dictionaries? `[{}]` **Consistency.** : Types in the schema are checked as types. Values are compared as values. Callables are called to validate. Simple. ## Other libraries and inspirations Voluptuous is heavily inspired by [Validino](http://code.google.com/p/validino/), and to a lesser extent, [jsonvalidator](http://code.google.com/p/jsonvalidator/) and [json\_schema](http://blog.sendapatch.se/category/json_schema.html). [pytest-voluptuous](https://github.com/F-Secure/pytest-voluptuous) is a [pytest](https://github.com/pytest-dev/pytest) plugin that helps in using voluptuous validators in `assert`s. I greatly prefer the light-weight style promoted by these libraries to the complexity of libraries like FormEncode.