I can successfully override __getitem__() for rvalues, but the following
example shows that more is required when used as an lvalue:
===8<-----
#!/usr/bin/env python
class Foo():
def __init__(self, n):
self.d = dict.fromkeys([i for i in range(0, n)])
def __getitem__(self, i):
return self.d[i]
def main():
foo = Foo(4)
print(foo[0])
foo[0] = 2 # not as an lvalue?
print(foo[0])
if __name__ == '__main__':
main()
===8<-----
Python 3.4 generates the following output when this example is executed:
None
Traceback (most recent call last):
File "./test.py", line 17, in <module>
main()
File "./test.py", line 13, in main
foo[0] = 2
TypeError: 'Foo' object does not support item assignment
I am surprised that the error states that the object itself cannot accept
assignment. From the C++ perspective, the underlying dictionary should be
exposed. Does Python overloading allow use of bracket overriding in
lvalues?
Thanks.
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