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"""
Checks that value used in a subscript supports subscription
(i.e. defines __getitem__ 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]
numbers[0]
"123"[0]
u"123"[0]
b"123"[0]
bytearray(b"123")[0]
dict(a=1, b=2)['a']
(1, 2, 3)[0]
# list/dict comprehensions are fine
[x for x in range(10)][0]
{x: 10 - x for x in range(10)}[0]
# instances
class NonSubscriptable(object):
pass
class Subscriptable(object):
def __getitem__(self, key):
return key + key
NonSubscriptable()[0] # [unsubscriptable-object]
NonSubscriptable[0] # [unsubscriptable-object]
Subscriptable()[0]
Subscriptable[0] # [unsubscriptable-object]
# generators are not subscriptable
def powers_of_two():
k = 0
while k < 10:
yield 2 ** k
k += 1
powers_of_two()[0] # [unsubscriptable-object]
powers_of_two[0] # [unsubscriptable-object]
# check that primitive non subscriptable types are catched
True[0] # [unsubscriptable-object]
None[0] # [unsubscriptable-object]
8.5[0] # [unsubscriptable-object]
10[0] # [unsubscriptable-object]
# sets are not subscriptable
{x ** 2 for x in range(10)}[0] # [unsubscriptable-object]
set(numbers)[0] # [unsubscriptable-object]
frozenset(numbers)[0] # [unsubscriptable-object]
# skip instances with unknown base classes
from some_missing_module import LibSubscriptable
class MaybeSubscriptable(LibSubscriptable):
pass
MaybeSubscriptable()[0]
# subscriptable classes (through metaclasses)
class MetaSubscriptable(type):
def __getitem__(cls, key):
return key + key
class SubscriptableClass(six.with_metaclass(MetaSubscriptable, object)):
pass
SubscriptableClass[0]
SubscriptableClass()[0] # [unsubscriptable-object]
# functions are not subscriptable
def test(*args, **kwargs):
return args, kwargs
test()[0]
test[0] # [unsubscriptable-object]
# deque
from collections import deque
deq = deque(maxlen=10)
deq.append(42)
deq[0]
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