On 14/09/12 22:16, Albert-Jan Roskam wrote:
Hi,
I defined a __getitem__ special method in a class that reads a binary data
file using a C library. The docstring should clarify the purpose of the
method. This works exactly as I intended it, however, the "key" argument is
actually used as an index (it also raises an IndexError when<key> is
greater than the number of records in the file). Am I abusing the __getitem__
method, or is this just a creative way of using it?
No, that's exactly what __getitem__ is for. It does double-duty for key-lookup
in mappings (dict[key]) and index-lookup in sequences (list[index]).
You can also support ranges of indexes by accepting a slice argument.
Another comment below:
# Python 2.6.4 (r264:75708, Oct 26 2009, 08:23:19) [MSC v.1500 32 bit (Intel)]
on win32
def __getitem__(self, key):
""" This function reports the record of case number<key>.
For example: firstRecord = FileReader(fileName)[0] """
if not isinstance(key, (int, float)):
raise TypeError
Floats? Do you actually have have case number (for example)
0.14285714285714285 ?
For this case, I think it is reasonable to insist on exactly an int,
and nothing else (except possibly a slice object, to support for
example obj[2:15]).
--
Steven
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