API Documentation¶
Validator Class¶
-
class
cerberus.
Validator
(*args, **kwargs)¶ Validator class. Normalizes and/or validates any mapping against a validation-schema which is provided as an argument at class instantiation or upon calling the
validate()
,validated()
ornormalized()
method. An instance itself is callable and executes a validation.All instantiation parameters are optional.
There are the introspective properties
types
,validators
,coercers
,default_setters
,rules
,normalization_rules
andvalidation_rules
.The attributes reflecting the available rules are assembled considering constraints that are defined in the docstrings of rules’ methods and is effectively used as validation schema for
schema
.Parameters: - schema (any mapping) – See
schema
. Defaults toNone
. - ignore_none_values (
bool
) – Seeignore_none_values
. Defaults toFalse
. - allow_unknown (
bool
or any mapping) – Seeallow_unknown
. Defaults toFalse
. - require_all (
bool
) – Seerequire_all
. Defaults toFalse
. - purge_unknown (
bool
) – Seepurge_unknown
. Defaults to toFalse
. - purge_readonly (
bool
) – Removes all fields that are defined asreadonly
in the normalization phase. - error_handler (class or instance based on
BaseErrorHandler
ortuple
) – The error handler that formats the result oferrors
. When given as two-value tuple with an error-handler class and a dictionary, the latter is passed to the initialization of the error handler. Default:BasicErrorHandler
.
-
_drop_remaining_rules
(*rules)¶ Drops rules from the queue of the rules that still need to be evaluated for the currently processed field. If no arguments are given, the whole queue is emptied.
-
_error
(*args)¶ Creates and adds one or multiple errors.
Parameters: args – Accepts different argument’s signatures.
1. Bulk addition of errors:
- iterable of
ValidationError
-instances
The errors will be added to
_errors
.2. Custom error:
- the invalid field’s name
- the error message
A custom error containing the message will be created and added to
_errors
. There will however be fewer information contained in the error (no reference to the violated rule and its constraint).3. Defined error:
- the invalid field’s name
- the error-reference, see
cerberus.errors
- arbitrary, supplemental information about the error
A
ValidationError
instance will be created and added to_errors
.- iterable of
-
_get_child_validator
(document_crumb=None, schema_crumb=None, **kwargs)¶ Creates a new instance of Validator-(sub-)class. All initial parameters of the parent are passed to the initialization, unless a parameter is given as an explicit keyword-parameter.
Parameters: Returns: an instance of
self.__class__
-
_lookup_field
(path)¶ Searches for a field as defined by path. This method is used by the
dependency
evaluation logic.Parameters: path ( str
) – Path elements are separated by a.
. A leading^
indicates that the path relates to the document root, otherwise it relates to the currently evaluated document, which is possibly a subdocument. The sequence^^
at the start will be interpreted as a literal^
.Returns: Either the found field name and its value or None
for both.Return type: A two-value tuple
.
-
allow_unknown
¶ If
True
unknown fields that are not defined in the schema will be ignored. If a mapping with a validation schema is given, any undefined field will be validated against its rules. Also see Allowing the Unknown. Type:bool
or any mapping
-
classmethod
clear_caches
()¶ Purge the cache of known valid schemas.
-
errors
¶ The errors of the last processing formatted by the handler that is bound to
error_handler
.
-
is_child
¶ True
for child-validators obtained with_get_child_validator()
. Type:bool
-
normalized
(document, schema=None, always_return_document=False)¶ Returns the document normalized according to the specified rules of a schema.
Parameters: Returns: A normalized copy of the provided mapping or
None
if an error occurred during normalization.
-
purge_unknown
¶ If
True
, unknown fields will be deleted from the document unless a validation is called with disabled normalization. Also see Purging Unknown Fields. Type:bool
-
root_allow_unknown
¶ The
allow_unknown
attribute of the first level ancestor of a child validator.
-
root_document
¶ The
document
attribute of the first level ancestor of a child validator.
-
root_require_all
¶ The
require_all
attribute of the first level ancestor of a child validator.
-
rules_set_registry
¶ The registry that holds referenced rules sets. Type:
Registry
-
schema
¶ The validation schema of a validator. When a schema is passed to a method, it replaces this attribute. Type: any mapping or
None
-
schema_registry
¶ The registry that holds referenced schemas. Type:
Registry
-
validate
(document, schema=None, update=False, normalize=True)¶ Normalizes and validates a mapping against a validation-schema of defined rules.
Parameters: - document (any mapping) – The document to normalize.
- schema (any mapping) – The validation schema. Defaults to
None
. If not provided here, the schema must have been provided at class instantiation. - update (
bool
) – IfTrue
, required fields won’t be checked. - normalize (
bool
) – IfTrue
, normalize the document before validation.
Returns: True
if validation succeeds, otherwiseFalse
. Check theerrors()
property for a list of processing errors.Return type:
-
validated
(*args, **kwargs)¶ Wrapper around
validate()
that returns the normalized and validated document orNone
if validation failed.
- schema (any mapping) – See
Rules Set & Schema Registry¶
-
class
cerberus.schema.
Registry
(definitions={})¶ A registry to store and retrieve schemas and parts of it by a name that can be used in validation schemas.
Parameters: definitions (any mapping) – Optional, initial definitions. -
add
(name, definition)¶ Register a definition to the registry. Existing definitions are replaced silently.
Parameters:
-
clear
()¶ Purge all definitions in the registry.
-
extend
(definitions)¶ Add several definitions at once. Existing definitions are replaced silently.
Parameters: definitions (a mapping or an iterable with two-value tuple
s) – The names and definitions.
-
get
(name, default=None)¶ Retrieve a definition from the registry.
Parameters: - name (
str
) – The reference that points to the definition. - default – Return value if the reference isn’t registered.
- name (
-
remove
(*names)¶ Unregister definitions from the registry.
Parameters: names – The names of the definitions that are to be unregistered.
-
Type Definitions¶
-
class
cerberus.
TypeDefinition
(name, included_types, excluded_types)¶ This class is used to define types that can be used as value in the
types_mapping
property. Thename
should be descriptive and match the key it is going to be assigned to. A value that is validated against such definition must be an instance of any of the types contained inincluded_types
and must not match any of the types contained inexcluded_types
.
Error Handlers¶
-
class
cerberus.errors.
BaseErrorHandler
(*args, **kwargs)¶ Base class for all error handlers. Subclasses are identified as error-handlers with an instance-test.
-
__call__
(errors)¶ Returns errors in a handler-specific format.
Parameters: errors (iterable of ValidationError
instances or aValidator
instance) – An object containing the errors.
-
__init__
(*args, **kwargs)¶ Optionally initialize a new instance.
-
__iter__
()¶ Be a superhero and implement an iterator over errors.
-
__weakref__
¶ list of weak references to the object (if defined)
-
add
(error)¶ Add an error to the errors’ container object of a handler.
Parameters: error ( ValidationError
) – The error to add.
-
emit
(error)¶ Optionally emits an error in the handler’s format to a stream. Or light a LED, or even shut down a power plant.
Parameters: error ( ValidationError
) – The error to emit.
-
end
(validator)¶ Gets called when a validation ends.
Parameters: validator ( Validator
) – The calling validator.
-
extend
(errors)¶ Adds all errors to the handler’s container object.
Parameters: errors (iterable of ValidationError
instances) – The errors to add.
-
Python Error Representations¶
-
class
cerberus.errors.
ErrorDefinition
(code, rule)¶ This class is used to define possible errors. Each distinguishable error is defined by a unique error
code
as integer and therule
that can cause it as string. The instances’ names do not contain a common prefix as they are supposed to be referenced within the module namespace, e.g.errors.CUSTOM
.
-
class
cerberus.errors.
ValidationError
(document_path, schema_path, code, rule, constraint, value, info)¶ A simple class to store and query basic error information.
-
child_errors
¶ A list that contains the individual errors of a bulk validation error.
-
constraint
= None¶ The constraint that failed.
-
definitions_errors
¶ Dictionary with errors of an *of-rule mapped to the index of the definition it occurred in. Returns
None
if not applicable.
-
is_group_error
¶ True
for errors of bulk validations.
-
is_logic_error
¶ True
for validation errors against different schemas with *of-rules.
-
is_normalization_error
¶ True
for normalization errors.
-
rule
= None¶ The rule that failed. Type: string
-
value
= None¶ The value that failed.
-
Error Codes¶
Its code
attribute uniquely identifies an
ErrorDefinition
that is used a concrete error’s
code
.
Some codes are actually reserved to mark a shared property of different errors.
These are useful as bitmasks while processing errors. This is the list of the
reserved codes:
0110 0000 |
0x60 |
96 | An error that occurred during normalization. |
1000 0000 |
0x80 |
128 | An error that contains child errors. |
1001 0000 |
0x90 |
144 | An error that was emitted by one of the *of-rules. |
None of these bits in the upper nibble must be used to enumerate error definitions, but only to mark one with the associated property.
Important
Users are advised to set bit 8 for self-defined errors. So the code
0001 0000 0001
/ 0x101
would the first in a domain-specific set of
error definitions.
This is a list of all error defintions that are shipped with the
errors
module:
Code (dec.) | Code (hex.) | Name | Rule |
---|---|---|---|
0 | 0x0 | CUSTOM | None |
2 | 0x2 | REQUIRED_FIELD | required |
3 | 0x3 | UNKNOWN_FIELD | None |
4 | 0x4 | DEPENDENCIES_FIELD | dependencies |
5 | 0x5 | DEPENDENCIES_FIELD_VALUE | dependencies |
6 | 0x6 | EXCLUDES_FIELD | excludes |
34 | 0x22 | EMPTY_NOT_ALLOWED | empty |
35 | 0x23 | NOT_NULLABLE | nullable |
36 | 0x24 | BAD_TYPE | type |
37 | 0x25 | BAD_TYPE_FOR_SCHEMA | schema |
38 | 0x26 | ITEMS_LENGTH | items |
39 | 0x27 | MIN_LENGTH | minlength |
40 | 0x28 | MAX_LENGTH | maxlength |
65 | 0x41 | REGEX_MISMATCH | regex |
66 | 0x42 | MIN_VALUE | min |
67 | 0x43 | MAX_VALUE | max |
68 | 0x44 | UNALLOWED_VALUE | allowed |
69 | 0x45 | UNALLOWED_VALUES | allowed |
70 | 0x46 | FORBIDDEN_VALUE | forbidden |
71 | 0x47 | FORBIDDEN_VALUES | forbidden |
72 | 0x48 | MISSING_MEMBERS | contains |
96 | 0x60 | NORMALIZATION | None |
97 | 0x61 | COERCION_FAILED | coerce |
98 | 0x62 | RENAMING_FAILED | rename_handler |
99 | 0x63 | READONLY_FIELD | readonly |
100 | 0x64 | SETTING_DEFAULT_FAILED | default_setter |
128 | 0x80 | ERROR_GROUP | None |
129 | 0x81 | MAPPING_SCHEMA | schema |
130 | 0x82 | SEQUENCE_SCHEMA | schema |
131 | 0x83 | KEYSRULES | keysrules |
131 | 0x83 | KEYSCHEMA | keysrules |
132 | 0x84 | VALUESRULES | valuesrules |
132 | 0x84 | VALUESCHEMA | valuesrules |
143 | 0x8f | BAD_ITEMS | items |
144 | 0x90 | LOGICAL | None |
145 | 0x91 | NONEOF | noneof |
146 | 0x92 | ONEOF | oneof |
147 | 0x93 | ANYOF | anyof |
148 | 0x94 | ALLOF | allof |
Error Containers¶
-
class
cerberus.errors.
ErrorList
¶ A list for
ValidationError
instances that can be queried with thein
keyword for a particularErrorDefinition
.
-
class
cerberus.errors.
ErrorTree
(errors=())¶ Base class for
DocumentErrorTree
andSchemaErrorTree
.-
add
(error)¶ Add an error to the tree.
Parameters: error – ValidationError
-
-
class
cerberus.errors.
DocumentErrorTree
(errors=())¶ Implements a dict-like class to query errors by indexes following the structure of a validated document.
-
class
cerberus.errors.
SchemaErrorTree
(errors=())¶ Implements a dict-like class to query errors by indexes following the structure of the used schema.
Exceptions¶
-
exception
cerberus.
SchemaError
¶ Raised when the validation schema is missing, has the wrong format or contains errors.
-
exception
cerberus.
DocumentError
¶ Raised when the target document is missing or has the wrong format
Utilities¶
-
class
cerberus.utils.
TypeDefinition
(name, included_types, excluded_types)¶ This class is used to define types that can be used as value in the
types_mapping
property. Thename
should be descriptive and match the key it is going to be assigned to. A value that is validated against such definition must be an instance of any of the types contained inincluded_types
and must not match any of the types contained inexcluded_types
.-
excluded_types
¶ Alias for field number 2
-
included_types
¶ Alias for field number 1
-
name
¶ Alias for field number 0
-
-
cerberus.utils.
mapping_to_frozenset
(mapping)¶ Be aware that this treats any sequence type with the equal members as equal. As it is used to identify equality of schemas, this can be considered okay as definitions are semantically equal regardless the container type.
-
class
cerberus.utils.
readonly_classproperty
¶
Schema Validation Schema¶
Against this schema validation schemas given to a vanilla
Validator
will be validated:
{'allof': {'logical': 'allof', 'type': 'list'},
'allow_unknown': {'oneof': [{'type': 'boolean'},
{'check_with': 'bulk_schema',
'type': ['dict', 'string']}]},
'allowed': {'type': 'container'},
'anyof': {'logical': 'anyof', 'type': 'list'},
'check_with': {'oneof': [{'type': 'callable'},
{'schema': {'oneof': [{'type': 'callable'},
{'allowed': (),
'type': 'string'}]},
'type': 'list'},
{'allowed': (), 'type': 'string'}]},
'coerce': {'oneof': [{'type': 'callable'},
{'schema': {'oneof': [{'type': 'callable'},
{'allowed': (),
'type': 'string'}]},
'type': 'list'},
{'allowed': (), 'type': 'string'}]},
'contains': {'empty': False},
'default': {'nullable': True},
'default_setter': {'oneof': [{'type': 'callable'},
{'allowed': (), 'type': 'string'}]},
'dependencies': {'check_with': 'dependencies',
'type': ('dict', 'hashable', 'list')},
'empty': {'type': 'boolean'},
'excludes': {'schema': {'type': 'hashable'},
'type': ('hashable', 'list')},
'forbidden': {'type': 'list'},
'items': {'check_with': 'items', 'type': 'list'},
'keysrules': {'check_with': 'bulk_schema',
'forbidden': ['rename', 'rename_handler'],
'type': ['dict', 'string']},
'max': {'nullable': False},
'maxlength': {'type': 'integer'},
'meta': {},
'min': {'nullable': False},
'minlength': {'type': 'integer'},
'noneof': {'logical': 'noneof', 'type': 'list'},
'nullable': {'type': 'boolean'},
'oneof': {'logical': 'oneof', 'type': 'list'},
'purge_unknown': {'type': 'boolean'},
'readonly': {'type': 'boolean'},
'regex': {'type': 'string'},
'rename': {'type': 'hashable'},
'rename_handler': {'oneof': [{'type': 'callable'},
{'schema': {'oneof': [{'type': 'callable'},
{'allowed': (),
'type': 'string'}]},
'type': 'list'},
{'allowed': (), 'type': 'string'}]},
'require_all': {'type': 'boolean'},
'required': {'type': 'boolean'},
'schema': {'anyof': [{'check_with': 'schema'},
{'check_with': 'bulk_schema'}],
'type': ['dict', 'string']},
'type': {'check_with': 'type', 'type': ['string', 'list']},
'valuesrules': {'check_with': 'bulk_schema',
'forbidden': ['rename', 'rename_handler'],
'type': ['dict', 'string']}}