Why aren't colons optional?

[Jason Orendorff]

Roy Smith wrote:
> Can you give me a practical example of why somebody would want to 
> define a __getitem__ method for a class?

To make objects that behave like lists or dictionaries, of course.

See e.g. the source code to the standard "os" module, where
os.environ is implemented as an instance of a class with a
__getitem__ method.

Or the standard "shelve" module, which provides a dictionary-like
object backed by a file.

Or a recent post on this newsgroup by Anton Vredegoor, where he
gave a class MenuChoice that had list-like behavior.

Etc.

## Jason Orendorff    http://www.jorendorff.com/