Source code for marshmallow.utils

"""Utility methods for marshmallow."""
import collections
import functools
import datetime
import inspect
import json
import re
from collections.abc import Mapping, Iterable
from email.utils import format_datetime, parsedate_to_datetime
from pprint import pprint as py_pprint

from marshmallow.base import FieldABC
from marshmallow.exceptions import FieldInstanceResolutionError

EXCLUDE = "exclude"
INCLUDE = "include"
RAISE = "raise"

dateutil_available = False
try:
    from dateutil import parser

    dateutil_available = True
except ImportError:
    dateutil_available = False


class _Missing:
    def __bool__(self):
        return False

    def __copy__(self):
        return self

    def __deepcopy__(self, _):
        return self

    def __repr__(self):
        return "<marshmallow.missing>"


# Singleton value that indicates that a field's value is missing from input
# dict passed to :meth:`Schema.load`. If the field's value is not required,
# it's ``default`` value is used.
missing = _Missing()


[docs]def is_generator(obj): """Return True if ``obj`` is a generator """ return inspect.isgeneratorfunction(obj) or inspect.isgenerator(obj)
[docs]def is_iterable_but_not_string(obj): """Return True if ``obj`` is an iterable object that isn't a string.""" return (isinstance(obj, Iterable) and not hasattr(obj, "strip")) or is_generator( obj )
[docs]def is_collection(obj): """Return True if ``obj`` is a collection type, e.g list, tuple, queryset.""" return is_iterable_but_not_string(obj) and not isinstance(obj, Mapping)
[docs]def is_instance_or_subclass(val, class_): """Return True if ``val`` is either a subclass or instance of ``class_``.""" try: return issubclass(val, class_) except TypeError: return isinstance(val, class_)
[docs]def is_keyed_tuple(obj): """Return True if ``obj`` has keyed tuple behavior, such as namedtuples or SQLAlchemy's KeyedTuples. """ return isinstance(obj, tuple) and hasattr(obj, "_fields")
[docs]def pprint(obj, *args, **kwargs): """Pretty-printing function that can pretty-print OrderedDicts like regular dictionaries. Useful for printing the output of :meth:`marshmallow.Schema.dump`. """ if isinstance(obj, collections.OrderedDict): print(json.dumps(obj, *args, **kwargs)) else: py_pprint(obj, *args, **kwargs)
# From pytz: http://pytz.sourceforge.net/ ZERO = datetime.timedelta(0) class UTC(datetime.tzinfo): """UTC Optimized UTC implementation. It unpickles using the single module global instance defined beneath this class declaration. """ zone = "UTC" _utcoffset = ZERO _dst = ZERO _tzname = zone def fromutc(self, dt): if dt.tzinfo is None: return self.localize(dt) return super(utc.__class__, self).fromutc(dt) def utcoffset(self, dt): return ZERO def tzname(self, dt): return "UTC" def dst(self, dt): return ZERO def localize(self, dt, is_dst=False): """Convert naive time to local time""" if dt.tzinfo is not None: raise ValueError("Not naive datetime (tzinfo is already set)") return dt.replace(tzinfo=self) def normalize(self, dt, is_dst=False): """Correct the timezone information on the given datetime""" if dt.tzinfo is self: return dt if dt.tzinfo is None: raise ValueError("Naive time - no tzinfo set") return dt.astimezone(self) def __repr__(self): return "<UTC>" def __str__(self): return "UTC" UTC = utc = UTC() # UTC is a singleton
[docs]def rfcformat(dt, *, localtime=False): """Return the RFC822-formatted representation of a datetime object. :param datetime dt: The datetime. :param bool localtime: If ``True``, return the date relative to the local timezone instead of UTC, displaying the proper offset, e.g. "Sun, 10 Nov 2013 08:23:45 -0600" """ if localtime and dt.tzinfo is None: dt = UTC.localize(dt) if not localtime and dt.tzinfo is not None: # Remove timezone to format as "-0000" rather than "+0000" dt = dt.astimezone(UTC).replace(tzinfo=None) return format_datetime(dt)
# From Django _iso8601_datetime_re = re.compile( r"(?P<year>\d{4})-(?P<month>\d{1,2})-(?P<day>\d{1,2})" r"[T ](?P<hour>\d{1,2}):(?P<minute>\d{1,2})" r"(?::(?P<second>\d{1,2})(?:\.(?P<microsecond>\d{1,6})\d{0,6})?)?" r"(?P<tzinfo>Z|[+-]\d{2}(?::?\d{2})?)?$" ) _iso8601_date_re = re.compile(r"(?P<year>\d{4})-(?P<month>\d{1,2})-(?P<day>\d{1,2})$") _iso8601_time_re = re.compile( r"(?P<hour>\d{1,2}):(?P<minute>\d{1,2})" r"(?::(?P<second>\d{1,2})(?:\.(?P<microsecond>\d{1,6})\d{0,6})?)?" )
[docs]def isoformat(dt, *args, localtime=False, **kwargs): """Return the ISO8601-formatted UTC representation of a datetime object.""" if localtime and dt.tzinfo is not None: localized = dt else: if dt.tzinfo is None: localized = UTC.localize(dt) else: localized = dt.astimezone(UTC) return localized.isoformat(*args, **kwargs)
[docs]def from_rfc(datestring): """Parse a RFC822-formatted datetime string and return a datetime object. https://stackoverflow.com/questions/885015/how-to-parse-a-rfc-2822-date-time-into-a-python-datetime """ return parsedate_to_datetime(datestring)
[docs]def from_iso_datetime(datetimestring, *, use_dateutil=True): """Parse an ISO8601-formatted datetime string and return a datetime object. Use dateutil's parser if possible and return a timezone-aware datetime. """ if not _iso8601_datetime_re.match(datetimestring): raise ValueError("Not a valid ISO8601-formatted datetime string") # Use dateutil's parser if possible if dateutil_available and use_dateutil: return parser.isoparse(datetimestring) else: # Strip off timezone info. if "." in datetimestring: # datetimestring contains microseconds return datetime.datetime.strptime( datetimestring[:26], "%Y-%m-%dT%H:%M:%S.%f" ) return datetime.datetime.strptime(datetimestring[:19], "%Y-%m-%dT%H:%M:%S")
[docs]def from_iso_time(timestring, *, use_dateutil=True): """Parse an ISO8601-formatted datetime string and return a datetime.time object. """ if not _iso8601_time_re.match(timestring): raise ValueError("Not a valid ISO8601-formatted time string") if dateutil_available and use_dateutil: return parser.parse(timestring).time() else: if len(timestring) > 8: # has microseconds fmt = "%H:%M:%S.%f" else: fmt = "%H:%M:%S" return datetime.datetime.strptime(timestring, fmt).time()
def from_iso_date(datestring, *, use_dateutil=True): if not _iso8601_date_re.match(datestring): raise ValueError("Not a valid ISO8601-formatted date string") if dateutil_available and use_dateutil: return parser.isoparse(datestring).date() else: return datetime.datetime.strptime(datestring[:10], "%Y-%m-%d").date() def to_iso_date(date, *args, **kwargs): return datetime.date.isoformat(date) def ensure_text_type(val): if isinstance(val, bytes): val = val.decode("utf-8") return str(val)
[docs]def pluck(dictlist, key): """Extracts a list of dictionary values from a list of dictionaries. :: >>> dlist = [{'id': 1, 'name': 'foo'}, {'id': 2, 'name': 'bar'}] >>> pluck(dlist, 'id') [1, 2] """ return [d[key] for d in dictlist]
# Various utilities for pulling keyed values from objects
[docs]def get_value(obj, key, default=missing): """Helper for pulling a keyed value off various types of objects. Fields use this method by default to access attributes of the source object. For object `x` and attribute `i`, this method first tries to access `x[i]`, and then falls back to `x.i` if an exception is raised. .. warning:: If an object `x` does not raise an exception when `x[i]` does not exist, `get_value` will never check the value `x.i`. Consider overriding `marshmallow.fields.Field.get_value` in this case. """ if not isinstance(key, int) and "." in key: return _get_value_for_keys(obj, key.split("."), default) else: return _get_value_for_key(obj, key, default)
def _get_value_for_keys(obj, keys, default): if len(keys) == 1: return _get_value_for_key(obj, keys[0], default) else: return _get_value_for_keys( _get_value_for_key(obj, keys[0], default), keys[1:], default ) def _get_value_for_key(obj, key, default): if not hasattr(obj, "__getitem__"): return getattr(obj, key, default) try: return obj[key] except (KeyError, IndexError, TypeError, AttributeError): return getattr(obj, key, default)
[docs]def set_value(dct, key, value): """Set a value in a dict. If `key` contains a '.', it is assumed be a path (i.e. dot-delimited string) to the value's location. :: >>> d = {} >>> set_value(d, 'foo.bar', 42) >>> d {'foo': {'bar': 42}} """ if "." in key: head, rest = key.split(".", 1) target = dct.setdefault(head, {}) if not isinstance(target, dict): raise ValueError( "Cannot set {key} in {head} " "due to existing value: {target}".format( key=key, head=head, target=target ) ) set_value(target, rest, value) else: dct[key] = value
[docs]def callable_or_raise(obj): """Check that an object is callable, else raise a :exc:`ValueError`. """ if not callable(obj): raise ValueError("Object {!r} is not callable.".format(obj)) return obj
def _signature(func): if hasattr(inspect, "signature"): return list(inspect.signature(func).parameters.keys()) if hasattr(func, "__self__"): # Remove bound arg to match inspect.signature() return inspect.getargspec(func).args[1:] # All args are unbound return inspect.getargspec(func).args
[docs]def get_func_args(func): """Given a callable, return a tuple of argument names. Handles `functools.partial` objects and class-based callables. .. versionchanged:: 3.0.0a1 Do not return bound arguments, eg. ``self``. """ if isinstance(func, functools.partial): return _signature(func.func) if inspect.isfunction(func) or inspect.ismethod(func): return _signature(func) # Callable class return _signature(func.__call__)
[docs]def resolve_field_instance(cls_or_instance): """Return a Schema instance from a Schema class or instance. :param type|Schema cls_or_instance: Marshmallow Schema class or instance. """ if isinstance(cls_or_instance, type): if not issubclass(cls_or_instance, FieldABC): raise FieldInstanceResolutionError return cls_or_instance() else: if not isinstance(cls_or_instance, FieldABC): raise FieldInstanceResolutionError return cls_or_instance