Range Operation pre-PEP

[Ben Hutchings]

Douglas Alan <nessus at mit.edu> writes:

> Ben Hutchings <ben.hutchings at roundpoint.com> writes:
> 
> > Douglas Alan <nessus at mit.edu> writes:
> 
> > > Speaking of creeping-featurism, how come we have list comprehension,
> > > but not tuple comprehension?  Seems inconsistent to me.
> 
> > A list contains a variable number of homogeneous values, e.g. the
> > lines of a file.  Lists are like arrays in other languages.  A tuple
> > contains a fixed number of heterogeneous values where each element
> > has a distinct meaning e.g. (year, month, day) for a date.
> 
> I think you have some other language in mind, rather than Python.  In
> Python, the only semantic difference between a list and a tuple is
> that a tuple is immutable.

Lists also have count() and index() methods, which tuples do not.
Doesn't this suggest a difference in intended purpose to you?

> > Tuples are like data structures or product types in other languages,
> > except that their types and fields are nameless.  Comprehensions
> > work with a variable number of homogeneous values, so they produce
> > lists.
> 
> filter() on a tuple returns a tuple.  The length of the tuple cannot
> be known in advance.
<snip>

Presumably filter() only requires its argument to be a sequence.

-- 
Any opinions expressed are my own and not necessarily those of Roundpoint.