"""Utility methods for marshmallow."""
from __future__ import annotations
import collections
import datetime as dt
import functools
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)
# 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)
def from_timestamp(value: typing.Any) -> dt.datetime:
value = float(value)
if value < 0:
raise ValueError("Not a valid POSIX timestamp")
# Load a timestamp with utc as timezone to prevent using system timezone.
# Then set timezone to None, to let the Field handle adding timezone info.
try:
return dt.datetime.fromtimestamp(value, tz=dt.timezone.utc).replace(tzinfo=None)
except OverflowError as exc:
raise ValueError("Timestamp is too large") from exc
except OSError as exc:
raise ValueError("Error converting value to datetime") from exc
def from_timestamp_ms(value: typing.Any) -> dt.datetime:
value = float(value)
return from_timestamp(value / 1000)
def timestamp(
value: dt.datetime,
) -> float:
if not is_aware(value):
# When a date is naive, use UTC as zone info to prevent using system timezone.
value = value.replace(tzinfo=dt.timezone.utc)
return value.timestamp()
def timestamp_ms(value: dt.datetime) -> float:
return timestamp(value) * 1000
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(
f"Cannot set {key} in {head} " f"due to existing value: {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
