Time (#482)

* adding python 3.5 as a target

* adding env flag

* Aligning on arrow dates.

lemur/common/fields.py

@@ -0,0 +1,93 @@
+import arrow
+import warnings
+from datetime import datetime as dt
+from marshmallow.fields import Field
+from marshmallow import utils
+
+
+class ArrowDateTime(Field):
+    """A formatted datetime string in UTC.
+
+    Example: ``'2014-12-22T03:12:58.019077+00:00'``
+
+    Timezone-naive `datetime` objects are converted to
+    UTC (+00:00) by :meth:`Schema.dump <marshmallow.Schema.dump>`.
+    :meth:`Schema.load <marshmallow.Schema.load>` returns `datetime`
+    objects that are timezone-aware.
+
+    :param str format: Either ``"rfc"`` (for RFC822), ``"iso"`` (for ISO8601),
+        or a date format string. If `None`, defaults to "iso".
+    :param kwargs: The same keyword arguments that :class:`Field` receives.
+
+    """
+
+    DATEFORMAT_SERIALIZATION_FUNCS = {
+        'iso': utils.isoformat,
+        'iso8601': utils.isoformat,
+        'rfc': utils.rfcformat,
+        'rfc822': utils.rfcformat,
+    }
+
+    DATEFORMAT_DESERIALIZATION_FUNCS = {
+        'iso': utils.from_iso,
+        'iso8601': utils.from_iso,
+        'rfc': utils.from_rfc,
+        'rfc822': utils.from_rfc,
+    }
+
+    DEFAULT_FORMAT = 'iso'
+
+    localtime = False
+    default_error_messages = {
+        'invalid': 'Not a valid datetime.',
+        'format': '"{input}" cannot be formatted as a datetime.',
+    }
+
+    def __init__(self, format=None, **kwargs):
+        super(ArrowDateTime, self).__init__(**kwargs)
+        # Allow this to be None. It may be set later in the ``_serialize``
+        # or ``_desrialize`` methods This allows a Schema to dynamically set the
+        # dateformat, e.g. from a Meta option
+        self.dateformat = format
+
+    def _add_to_schema(self, field_name, schema):
+        super(ArrowDateTime, self)._add_to_schema(field_name, schema)
+        self.dateformat = self.dateformat or schema.opts.dateformat
+
+    def _serialize(self, value, attr, obj):
+        if value is None:
+            return None
+        self.dateformat = self.dateformat or self.DEFAULT_FORMAT
+        format_func = self.DATEFORMAT_SERIALIZATION_FUNCS.get(self.dateformat, None)
+        if format_func:
+            try:
+                return format_func(value, localtime=self.localtime)
+            except (AttributeError, ValueError) as err:
+                self.fail('format', input=value)
+        else:
+            return value.strftime(self.dateformat)
+
+    def _deserialize(self, value, attr, data):
+        if not value:  # Falsy values, e.g. '', None, [] are not valid
+            raise self.fail('invalid')
+        self.dateformat = self.dateformat or self.DEFAULT_FORMAT
+        func = self.DATEFORMAT_DESERIALIZATION_FUNCS.get(self.dateformat)
+        if func:
+            try:
+                return arrow.get(func(value))
+            except (TypeError, AttributeError, ValueError):
+                raise self.fail('invalid')
+        elif self.dateformat:
+            try:
+                return dt.datetime.strptime(value, self.dateformat)
+            except (TypeError, AttributeError, ValueError):
+                raise self.fail('invalid')
+        elif utils.dateutil_available:
+            try:
+                return arrow.get(utils.from_datestring(value))
+            except TypeError:
+                raise self.fail('invalid')
+        else:
+            warnings.warn('It is recommended that you install python-dateutil '
+                          'for improved datetime deserialization.')
+            raise self.fail('invalid')