Make better loop performance more intuitive

.travis.yml

@@ -1,14 +1,11 @@
 language: python
 sudo: false
-addons:
-  apt:
-    sources:
-      - deadsnakes
-    packages:
-      - python3.5
 python:
   - "2.7"
+  - "3.5"
+  - "pypy"
+  - "pypy3"
 install:
-  - pip install tox
+  - pip install tox-travis
 script:
   - tox

README.rst

@@ -14,22 +14,22 @@ for Python (supporting 2.7+ including Python 3).
 
 .. code-block:: python
 
-    >>> from jsonschema import validate
+    >>> from jsonschema import Schema
 
     >>> # A sample schema, like what we'd get from json.load()
-    >>> schema = {
+    >>> schema = Schema({
     ...     "type" : "object",
     ...     "properties" : {
     ...         "price" : {"type" : "number"},
     ...         "name" : {"type" : "string"},
     ...     },
-    ... }
+    ... })
 
     >>> # If no exception is raised by validate(), the instance is valid.
-    >>> validate({"name" : "Eggs", "price" : 34.99}, schema)
+    >>> schema.validate({"name" : "Eggs", "price" : 34.99})
 
-    >>> validate(
-    ...     {"name" : "Eggs", "price" : "Invalid"}, schema
+    >>> schema.validate(
+    ...     {"name" : "Eggs", "price" : "Invalid"}
     ... )                                   # doctest: +IGNORE_EXCEPTION_DETAIL
     Traceback (most recent call last):
         ...

docs/index.rst

@@ -11,22 +11,22 @@ for Python (supporting 2.7+ including Python 3).
 
 .. code-block:: python
 
-    >>> from jsonschema import validate
+    >>> from jsonschema import Schema
 
     >>> # A sample schema, like what we'd get from json.load()
-    >>> schema = {
+    >>> schema = Schema({
     ...     "type" : "object",
     ...     "properties" : {
     ...         "price" : {"type" : "number"},
     ...         "name" : {"type" : "string"},
     ...     },
-    ... }
+    ... })
 
     >>> # If no exception is raised by validate(), the instance is valid.
-    >>> validate({"name" : "Eggs", "price" : 34.99}, schema)
+    >>> schema.validate({"name" : "Eggs", "price" : 34.99})
 
-    >>> validate(
-    ...     {"name" : "Eggs", "price" : "Invalid"}, schema
+    >>> schema.validate(
+    ...     {"name" : "Eggs", "price" : "Invalid"}
     ... )                                   # doctest: +IGNORE_EXCEPTION_DETAIL
     Traceback (most recent call last):
         ...

jsonschema/__init__.py

@@ -16,7 +16,7 @@
     FormatChecker, draft3_format_checker, draft4_format_checker,
 )
 from jsonschema.validators import (
-    Draft3Validator, Draft4Validator, RefResolver, validate
+    Draft3Validator, Draft4Validator, RefResolver, validate, Schema
 )
 
 from jsonschema._version import __version__

jsonschema/exceptions.py

@@ -85,7 +85,7 @@ def __unicode__(self):
         __str__ = __unicode__
     else:
         def __str__(self):
-            return unicode(self).encode("utf-8")
+            return self.__unicode__().encode("utf-8")
 
     @classmethod
     def create_from(cls, other):
@@ -158,7 +158,7 @@ def __unicode__(self):
         __str__ = __unicode__
     else:
         def __str__(self):
-            return unicode(self).encode("utf-8")
+            return self.__unicode__().encode("utf-8")
 
 
 class FormatError(Exception):
@@ -174,7 +174,7 @@ def __unicode__(self):
         __str__ = __unicode__
     else:
         def __str__(self):
-            return self.message.encode("utf-8")
+            return self.__unicode__().encode("utf-8")
 
 
 class ErrorTree(object):

jsonschema/tests/test_validators.py

@@ -7,6 +7,7 @@
 from jsonschema.validators import (
     RefResolutionError, UnknownType, Draft3Validator,
     Draft4Validator, RefResolver, create, extend, validator_for, validate,
+    Schema,
 )
 
 
@@ -759,6 +760,14 @@ def test_draft4_validator_is_the_default(self):
             chk_schema.assert_called_once_with({})
 
 
+class TestSchemaCls(unittest.TestCase):
+    def test_draft4_validator_is_the_default_for_schema_cls(self):
+        with mock.patch.object(Draft4Validator, "check_schema") as chk_schema:
+            schema = Schema({})
+            schema.validate({})
+            chk_schema.assert_called_once_with({})
+
+
 class TestRefResolver(unittest.TestCase):
 
     base_uri = ""

jsonschema/validators.py

@@ -539,3 +539,36 @@ def validate(instance, schema, cls=None, *args, **kwargs):
         cls = validator_for(schema)
     cls.check_schema(schema)
     cls(schema, *args, **kwargs).validate(instance)
+
+
+class Schema(object):
+    """
+    Similar to :func:`validate`, except the :class:`IValidator` is initialized
+    only once when this class is initialized. This can be useful for improving
+    the performance of validation in loops.
+
+    :argument schema: the schema to validate with
+    :argument validator_cls: an :class:`IValidator` class that will be used by
+                             :meth:`validate` to validate the instance.
+
+    :raises:
+        :exc:`SchemaError` if the schema itself is invalid
+    """
+
+    def __init__(self, schema, validator_cls=None, *args, **kwargs):
+        if validator_cls is None:
+            validator_cls = validator_for(schema)
+        validator_cls.check_schema(schema)
+        self.validator = validator_cls(schema, *args, **kwargs)
+
+    def validate(self, instance):
+        """
+        Validate an instance with the schema and :class:`IValidator` class used
+        in this instance of :class:`Schema`.
+
+        :argument instance: the instance to validate
+
+        :raises:
+            :exc:`ValidationError` if the instance is invalid
+        """
+        self.validator.validate(instance)

tox.ini

@@ -1,6 +1,9 @@
 [tox]
 envlist = py{27,35,py,py3}, docs, style
 
+[tox:travis]
+2.7 = py27, style
+3.5 = py35, docs, style
 
 [testenv]
 setenv =