py3k printing generators -- not!
tjreedy at udel.edu
Sun Jun 7 00:58:09 CEST 2009
> The one thing that's killing me in Python 3000
py3.0 or py3.1, but the 'problem' you complain about has nothing to do
with those versions in particular.
> is that every time I try to print something, it seems like I get <generator object
> <genexpr> at 0x01BAF508>.
Nor does it have anything is particular to do with generator objects.
Str(function/class/module/and-many-others) prints similarly. Since
forever, str(ob) == ob.__str__() == type(ob).__str__(ob). And what you
see above is the default template filled in for a particular object.
Built-in concrete collections over-ride the default and return a string
with their contents because they can do that without harm other than
possibly producing a very long string. When the collections are large,
one might want a custom function that instead formats a string with a
limited number of examples and the total count.
A 3.0 range object, a virtual collection, could do that too, but since
there is a regular pattern, it prints a condensed representation.
Aren't you glad, actually, that range(1000000000) prints as "range(0,
1000000000)" instead of listing the billion numbers it produces when
iterated, as you seem to be asking for?
> Googling only found one reference, a
> posting elsewhere by one Carl Johnson (aka carlj7,
A bogus complaint that the constructor for highly specialized class str
acts differently from those of the general collection classes set,
tuple, and list. Str is actually not a collection class in the way that
set, tuple, list, dict, and many others are.
Terry Jan Reedy
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