Source code for marshmallow.utils

"""Utility methods for marshmallow."""
from __future__ import annotations

import collections
import functools
import datetime as dt
import inspect
import json
import re
import typing
import warnings
from collections.abc import Mapping
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
from marshmallow.warnings import RemovedInMarshmallow4Warning

EXCLUDE = "exclude"
INCLUDE = "include"
RAISE = "raise"
_UNKNOWN_VALUES = {EXCLUDE, INCLUDE, RAISE}


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) -> bool: """Return True if ``obj`` is a generator""" return inspect.isgeneratorfunction(obj) or inspect.isgenerator(obj)
[docs]def is_iterable_but_not_string(obj) -> bool: """Return True if ``obj`` is an iterable object that isn't a string.""" return (hasattr(obj, "__iter__") and not hasattr(obj, "strip")) or is_generator(obj)
[docs]def is_collection(obj) -> bool: """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_) -> bool: """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) -> bool: """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) -> None: """Pretty-printing function that can pretty-print OrderedDicts like regular dictionaries. Useful for printing the output of :meth:`marshmallow.Schema.dump`. .. deprecated:: 3.7.0 marshmallow.pprint will be removed in marshmallow 4. """ warnings.warn( "marshmallow's pprint function is deprecated and will be removed in marshmallow 4.", RemovedInMarshmallow4Warning, stacklevel=2, ) if isinstance(obj, collections.OrderedDict): print(json.dumps(obj, *args, **kwargs)) else: py_pprint(obj, *args, **kwargs)
# https://stackoverflow.com/a/27596917 def is_aware(datetime: dt.datetime) -> bool: return ( datetime.tzinfo is not None and datetime.tzinfo.utcoffset(datetime) is not None )
[docs]def from_rfc(datestring: str) -> dt.datetime: """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 # noqa: B950 """ return parsedate_to_datetime(datestring)
[docs]def rfcformat(datetime: dt.datetime) -> str: """Return the RFC822-formatted representation of a datetime object. :param datetime datetime: The datetime. """ return format_datetime(datetime)
# Hat tip to Django for ISO8601 deserialization functions _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 get_fixed_timezone(offset: int | float | dt.timedelta) -> dt.timezone: """Return a tzinfo instance with a fixed offset from UTC.""" if isinstance(offset, dt.timedelta): offset = offset.total_seconds() // 60 sign = "-" if offset < 0 else "+" hhmm = "%02d%02d" % divmod(abs(offset), 60) name = sign + hhmm return dt.timezone(dt.timedelta(minutes=offset), name)
[docs]def from_iso_datetime(value): """Parse a string and return a datetime.datetime. This function supports time zone offsets. When the input contains one, the output uses a timezone with a fixed offset from UTC. """ match = _iso8601_datetime_re.match(value) if not match: raise ValueError("Not a valid ISO8601-formatted datetime string") kw = match.groupdict() kw["microsecond"] = kw["microsecond"] and kw["microsecond"].ljust(6, "0") tzinfo = kw.pop("tzinfo") if tzinfo == "Z": tzinfo = dt.timezone.utc elif tzinfo is not None: offset_mins = int(tzinfo[-2:]) if len(tzinfo) > 3 else 0 offset = 60 * int(tzinfo[1:3]) + offset_mins if tzinfo[0] == "-": offset = -offset tzinfo = get_fixed_timezone(offset) kw = {k: int(v) for k, v in kw.items() if v is not None} kw["tzinfo"] = tzinfo return dt.datetime(**kw)
[docs]def from_iso_time(value): """Parse a string and return a datetime.time. This function doesn't support time zone offsets. """ match = _iso8601_time_re.match(value) if not match: raise ValueError("Not a valid ISO8601-formatted time string") kw = match.groupdict() kw["microsecond"] = kw["microsecond"] and kw["microsecond"].ljust(6, "0") kw = {k: int(v) for k, v in kw.items() if v is not None} return dt.time(**kw)
[docs]def from_iso_date(value): """Parse a string and return a datetime.date.""" match = _iso8601_date_re.match(value) if not match: raise ValueError("Not a valid ISO8601-formatted date string") kw = {k: int(v) for k, v in match.groupdict().items()} return dt.date(**kw)
[docs]def isoformat(datetime: dt.datetime) -> str: """Return the ISO8601-formatted representation of a datetime object. :param datetime datetime: The datetime. """ return datetime.isoformat()
def to_iso_time(time: dt.time) -> str: return dt.time.isoformat(time) def to_iso_date(date: dt.date) -> str: return dt.date.isoformat(date) def ensure_text_type(val: str | bytes) -> str: if isinstance(val, bytes): val = val.decode("utf-8") return str(val)
[docs]def pluck(dictlist: list[dict[str, typing.Any]], key: str): """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: int | str, 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: dict[str, typing.Any], key: str, value: typing.Any): """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:`TypeError`.""" if not callable(obj): raise TypeError(f"Object {obj!r} is not callable.") return obj
def _signature(func: typing.Callable) -> list[str]: return list(inspect.signature(func).parameters.keys())
[docs]def get_func_args(func: typing.Callable) -> list[str]: """Given a callable, return a list of argument names. Handles `functools.partial` objects and class-based callables. .. versionchanged:: 3.0.0a1 Do not return bound arguments, eg. ``self``. """ if inspect.isfunction(func) or inspect.ismethod(func): return _signature(func) if isinstance(func, functools.partial): return _signature(func.func) # Callable class return _signature(func)
[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
[docs]def timedelta_to_microseconds(value: dt.timedelta) -> int: """Compute the total microseconds of a timedelta https://github.com/python/cpython/blob/bb3e0c240bc60fe08d332ff5955d54197f79751c/Lib/datetime.py#L665-L667 # noqa: B950 """ return (value.days * (24 * 3600) + value.seconds) * 1000000 + value.microseconds
def validate_unknown_parameter_value(obj: typing.Any) -> str: if obj not in _UNKNOWN_VALUES: raise ValueError( f"Object {obj!r} is not a valid value for the 'unknown' parameter" ) return obj