Why tuple with one item is no tuple
daniel at dittmar.net
Thu Mar 17 00:00:51 CET 2005
Diez B. Roggisch wrote:
> I reread his example and have to admit I'm confused: He complains about
> having written his _own_ vector class - and concatenation and addition had
> to use both + ?
I've interpreted it as:
If Python had choosen different operators for addition and sequence
concatenation, I could have implemented them both in my vector class. As
it is, I have to implement one of them using a non-standard operator.
> The examples focus too much on numbers - if we use instead
> we would get a iterable yielding ["foo",] or - as string already supports
> iteration - ['f', 'o', 'o']. Which one to chose?
What I was hinting at (NOT proposing, I'd hate this) was that integers
implement the  operator. 5  would then return 5, for all practical
purposes, it would look like a tuple. String already implements . Yes,
that would lead to really surprising and inconsistent behaviour.
>>I find this 'creative use of overloading' rather awful. But what the
>>heck, I find list comprehension rather awful.
> Well, the number of operators built into the language is limited - and I
> actually prefer to have the possibility to overload these if I want to.
> Nobody forces me - I could use
> for two vectors v1, v2 if I wanted to.
My peeve is about having operators added to standard types. This
increases the chances that using an object the wrong way leads to a
bogus result, not a runtime error. A more common programming error I
commit is passing a string where a list ist expected. And then I wonder
why later operations work on one-character strings.
Operator overloading is certainly an irregular verb:
- I make the usage more intuitive
- Yours may lead to misinterpretation
- He obfuscates
More information about the Python-list