On 6/29/2012 6:45 AM Albert-Jan Roskam said...
Hi Steven, Thanks for helping me. It makes more sense now. Calling append() on the datatype list returns None but calling __add__ on the datatype int returns, well, the result.
I don't know that it's consistent across all types, but I've found that mutable types tend to change in place and return None while immutable types tend to return the altered result, which is as you describe below.
Emile
Somehow it makes more sense to me when writing + as __add__ a[k] = a.get(k, 0).__add__(1) b[k] = b.get(k, []]).__add__([v]) >>> x = 1 >>> y = [] >>> z = y.append(x) >>> z is None True Regards, Albert-Jan
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