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"""
Checks that value used in a subscript support deletion
(i.e. defines __delitem__ method).
"""
# pylint: disable=missing-docstring,pointless-statement,expression-not-assigned,wrong-import-position
# pylint: disable=too-few-public-methods,import-error,invalid-name,wrong-import-order
import six
# primitives
numbers = [1, 2, 3]
del numbers[0]
del bytearray(b"123")[0]
del dict(a=1, b=2)['a']
del (1, 2, 3)[0] # [unsupported-delete-operation]
# list/dict comprehensions are fine
del [x for x in range(10)][0]
del {x: 10 - x for x in range(10)}[0]
# instances
class NonSubscriptable(object):
pass
class Subscriptable(object):
def __delitem__(self, key):
pass
del NonSubscriptable()[0] # [unsupported-delete-operation]
del NonSubscriptable[0] # [unsupported-delete-operation]
del Subscriptable()[0]
del Subscriptable[0] # [unsupported-delete-operation]
# generators are not subscriptable
def powers_of_two():
k = 0
while k < 10:
yield 2 ** k
k += 1
del powers_of_two()[0] # [unsupported-delete-operation]
del powers_of_two[0] # [unsupported-delete-operation]
# check that primitive non subscriptable types are catched
del True[0] # [unsupported-delete-operation]
del None[0] # [unsupported-delete-operation]
del 8.5[0] # [unsupported-delete-operation]
del 10[0] # [unsupported-delete-operation]
# sets are not subscriptable
del {x ** 2 for x in range(10)}[0] # [unsupported-delete-operation]
del set(numbers)[0] # [unsupported-delete-operation]
del frozenset(numbers)[0] # [unsupported-delete-operation]
# skip instances with unknown base classes
from some_missing_module import LibSubscriptable
class MaybeSubscriptable(LibSubscriptable):
pass
del MaybeSubscriptable()[0]
# subscriptable classes (through metaclasses)
class MetaSubscriptable(type):
def __delitem__(cls, key):
pass
class SubscriptableClass(six.with_metaclass(MetaSubscriptable, object)):
pass
del SubscriptableClass[0]
del SubscriptableClass()[0] # [unsupported-delete-operation]
# functions are not subscriptable
def test(*args, **kwargs):
return args, kwargs
del test()[0] # [unsupported-delete-operation]
del test[0] # [unsupported-delete-operation]
# deque
from collections import deque
deq = deque(maxlen=10)
deq.append(42)
del deq[0]
# tuples assignment
values = [1, 2, 3, 4]
del (values[0], values[1])
del (values[0], SubscriptableClass()[0]) # [unsupported-delete-operation]
|
