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bpo-32499: Add dataclasses.is_dataclass(obj), which returns True if obj is a dataclass or an instance of one. (#5113)

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Eric V. Smith 2018-01-06 12:41:53 -05:00 • committed by GitHub
parent 3cd7c6e6eb
commit e7ba013d87
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3 changed files with 36 additions and 22 deletions
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37
Lib/test/test_dataclasses.py
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@ -1,6 +1,6 @@
from dataclasses import (
dataclass, field, FrozenInstanceError, fields, asdict, astuple,
make_dataclass, replace, InitVar, Field, MISSING
make_dataclass, replace, InitVar, Field, MISSING, is_dataclass,
)
import pickle
@ -1365,27 +1365,32 @@ class TestCase(unittest.TestCase):
self.assertIs(C().x, int)
def test_isdataclass(self):
# There is no isdataclass() helper any more, but the PEP
# describes how to write it, so make sure that works. Note
# that this version returns True for both classes and
# instances.
def isdataclass(obj):
try:
fields(obj)
return True
except TypeError:
return False
def test_is_dataclass(self):
class NotDataClass:
pass
self.assertFalse(isdataclass(0))
self.assertFalse(isdataclass(int))
self.assertFalse(is_dataclass(0))
self.assertFalse(is_dataclass(int))
self.assertFalse(is_dataclass(NotDataClass))
self.assertFalse(is_dataclass(NotDataClass()))
@dataclass
class C:
x: int
self.assertTrue(isdataclass(C))
self.assertTrue(isdataclass(C(0)))
@dataclass
class D:
d: C
e: int
c = C(10)
d = D(c, 4)
self.assertTrue(is_dataclass(C))
self.assertTrue(is_dataclass(c))
self.assertFalse(is_dataclass(c.x))
self.assertTrue(is_dataclass(d.d))
self.assertFalse(is_dataclass(d.e))
def test_helper_fields_with_class_instance(self):
# Check that we can call fields() on either a class or instance,