Shortcuts on this page
r m x toggle line displays
j k next/prev highlighted chunk
0 (zero) top of page
1 (one) first highlighted chunk
1# ___
2# \./ DANGER: This project implements some code generation
3# .--.O.--. techniques involving string concatenation.
4# \/ \/ If you look at it, you might die.
5#
7r"""
8Installation
9************
11.. code-block:: bash
13 pip install fastjsonschema
15Support only for Python 3.3 and higher.
17About
18*****
20``fastjsonschema`` implements validation of JSON documents by JSON schema.
21The library implements JSON schema drafts 04, 06, and 07. The main purpose is
22to have a really fast implementation. See some numbers:
24 * Probably the most popular, ``jsonschema``, can take up to 5 seconds for valid
25 inputs and 1.2 seconds for invalid inputs.
26 * Second most popular, ``json-spec``, is even worse with up to 7.2 and 1.7 seconds.
27 * Last ``validictory``, now deprecated, is much better with 370 or 23 milliseconds,
28 but it does not follow all standards, and it can be still slow for some purposes.
30With this library you can gain big improvements as ``fastjsonschema`` takes
31only about 25 milliseconds for valid inputs and 2 milliseconds for invalid ones.
32Pretty amazing, right? :-)
34Technically it works by generating the most stupid code on the fly, which is fast but
35is hard to write by hand. The best efficiency is achieved when a validator is compiled
36once and used many times, of course. It works similarly like regular expressions. But
37you can also generate the code to a file, which is even slightly faster.
39You can run the performance benchmarks on your computer or server with the included
40script:
42.. code-block:: bash
44 $ make performance
45 fast_compiled valid ==> 0.0993900
46 fast_compiled invalid ==> 0.0041089
47 fast_compiled_without_exc valid ==> 0.0465258
48 fast_compiled_without_exc invalid ==> 0.0023688
49 fast_file valid ==> 0.0989483
50 fast_file invalid ==> 0.0041104
51 fast_not_compiled valid ==> 11.9572681
52 fast_not_compiled invalid ==> 2.9512092
53 jsonschema valid ==> 5.2233240
54 jsonschema invalid ==> 1.3227916
55 jsonschema_compiled valid ==> 0.4447982
56 jsonschema_compiled invalid ==> 0.0231333
57 jsonspec valid ==> 4.1450569
58 jsonspec invalid ==> 1.0485777
59 validictory valid ==> 0.2730411
60 validictory invalid ==> 0.0183669
62This library follows and implements `JSON schema draft-04, draft-06, and draft-07
63<http://json-schema.org>`_. Sometimes it's not perfectly clear, so I recommend also
64check out this `understanding JSON schema <https://spacetelescope.github.io/understanding-json-schema>`_.
66Note that there are some differences compared to JSON schema standard:
68 * Regular expressions are full Python ones, not only what JSON schema allows. It's easier
69 to allow everything, and also it's faster to compile without limits. So keep in mind that when
70 you will use a more advanced regular expression, it may not work with other libraries or in
71 other languages.
72 * Because Python matches new line for a dollar in regular expressions (``a$`` matches ``a`` and ``a\\n``),
73 instead of ``$`` is used ``\Z`` and all dollars in your regular expression are changed to ``\\Z``
74 as well. When you want to use dollar as regular character, you have to escape it (``\$``).
75 * JSON schema says you can use keyword ``default`` for providing default values. This implementation
76 uses that and always returns transformed input data.
78Usage
79*****
81.. code-block:: python
83 import fastjsonschema
85 point_schema = {
86 "type": "object",
87 "properties": {
88 "x": {
89 "type": "number",
90 },
91 "y": {
92 "type": "number",
93 },
94 },
95 "required": ["x", "y"],
96 "additionalProperties": False,
97 }
99 point_validator = fastjsonschema.compile(point_schema)
100 try:
101 point_validator({"x": 1.0, "y": 2.0})
102 except fastjsonschema.JsonSchemaException as e:
103 print(f"Data failed validation: {e}")
105API
106***
107"""
108from functools import partial, update_wrapper
110from .draft04 import CodeGeneratorDraft04
111from .draft06 import CodeGeneratorDraft06
112from .draft07 import CodeGeneratorDraft07
113from .exceptions import JsonSchemaException, JsonSchemaValueException, JsonSchemaDefinitionException
114from .ref_resolver import RefResolver
115from .version import VERSION
117__all__ = (
118 'VERSION',
119 'JsonSchemaException',
120 'JsonSchemaValueException',
121 'JsonSchemaDefinitionException',
122 'validate',
123 'compile',
124 'compile_to_code',
125)
128def validate(definition, data, handlers={}, formats={}, use_default=True, use_formats=True, detailed_exceptions=True):
129 """
130 Validation function for lazy programmers or for use cases when you need
131 to call validation only once, so you do not have to compile it first.
132 Use it only when you do not care about performance (even though it will
133 be still faster than alternative implementations).
135 .. code-block:: python
137 import fastjsonschema
139 fastjsonschema.validate({'type': 'string'}, 'hello')
140 # same as: compile({'type': 'string'})('hello')
142 Preferred is to use :any:`compile` function.
143 """
144 return compile(definition, handlers, formats, use_default, use_formats, detailed_exceptions)(data)
147#TODO: Change use_default to False when upgrading to version 3.
148# pylint: disable=redefined-builtin,dangerous-default-value,exec-used
149def compile(definition, handlers={}, formats={}, use_default=True, use_formats=True, detailed_exceptions=True):
150 """
151 Generates validation function for validating JSON schema passed in ``definition``.
152 Example:
154 .. code-block:: python
156 import fastjsonschema
158 validate = fastjsonschema.compile({'type': 'string'})
159 validate('hello')
161 This implementation supports keyword ``default`` (can be turned off
162 by passing `use_default=False`):
164 .. code-block:: python
166 validate = fastjsonschema.compile({
167 'type': 'object',
168 'properties': {
169 'a': {'type': 'number', 'default': 42},
170 },
171 })
173 data = validate({})
174 assert data == {'a': 42}
176 Supported implementations are draft-04, draft-06 and draft-07. Which version
177 should be used is determined by `$draft` in your ``definition``. When not
178 specified, the latest implementation is used (draft-07).
180 .. code-block:: python
182 validate = fastjsonschema.compile({
183 '$schema': 'http://json-schema.org/draft-04/schema',
184 'type': 'number',
185 })
187 You can pass mapping from URI to function that should be used to retrieve
188 remote schemes used in your ``definition`` in parameter ``handlers``.
190 Also, you can pass mapping for custom formats. Key is the name of your
191 formatter and value can be regular expression, which will be compiled or
192 callback returning `bool` (or you can raise your own exception).
194 .. code-block:: python
196 validate = fastjsonschema.compile(definition, formats={
197 'foo': r'foo|bar',
198 'bar': lambda value: value in ('foo', 'bar'),
199 })
201 Note that formats are automatically used as assertions. It can be turned
202 off by passing `use_formats=False`. When disabled, custom formats are
203 disabled as well. (Added in 2.19.0.)
205 If you don't need detailed exceptions, you can turn the details off and gain
206 additional performance by passing `detailed_exceptions=False`.
208 Exception :any:`JsonSchemaDefinitionException` is raised when generating the
209 code fails (bad definition).
211 Exception :any:`JsonSchemaValueException` is raised from generated function when
212 validation fails (data do not follow the definition).
213 """
214 resolver, code_generator = _factory(definition, handlers, formats, use_default, use_formats, detailed_exceptions)
215 global_state = code_generator.global_state
216 # Do not pass local state so it can recursively call itself.
217 exec(code_generator.func_code, global_state)
218 func = global_state[resolver.get_scope_name()]
219 if formats:
220 return update_wrapper(partial(func, custom_formats=formats), func)
221 return func
224# pylint: disable=dangerous-default-value
225def compile_to_code(definition, handlers={}, formats={}, use_default=True, use_formats=True, detailed_exceptions=True):
226 """
227 Generates validation code for validating JSON schema passed in ``definition``.
228 Example:
230 .. code-block:: python
232 import fastjsonschema
234 code = fastjsonschema.compile_to_code({'type': 'string'})
235 with open('your_file.py', 'w') as f:
236 f.write(code)
238 You can also use it as a script:
240 .. code-block:: bash
242 echo "{'type': 'string'}" | python3 -m fastjsonschema > your_file.py
243 python3 -m fastjsonschema "{'type': 'string'}" > your_file.py
245 Exception :any:`JsonSchemaDefinitionException` is raised when generating the
246 code fails (bad definition).
247 """
248 _, code_generator = _factory(definition, handlers, formats, use_default, use_formats, detailed_exceptions)
249 return (
250 'VERSION = "' + VERSION + '"\n' +
251 code_generator.global_state_code + '\n' +
252 code_generator.func_code
253 )
256def _factory(definition, handlers, formats={}, use_default=True, use_formats=True, detailed_exceptions=True):
257 resolver = RefResolver.from_schema(definition, handlers=handlers, store={})
258 code_generator = _get_code_generator_class(definition)(
259 definition,
260 resolver=resolver,
261 formats=formats,
262 use_default=use_default,
263 use_formats=use_formats,
264 detailed_exceptions=detailed_exceptions,
265 )
266 return resolver, code_generator
269def _get_code_generator_class(schema):
270 # Schema in from draft-06 can be just the boolean value.
271 if isinstance(schema, dict):
272 schema_version = schema.get('$schema', '')
273 if 'draft-04' in schema_version:
274 return CodeGeneratorDraft04
275 if 'draft-06' in schema_version:
276 return CodeGeneratorDraft06
277 return CodeGeneratorDraft07