Jean-Paul Calderone wrote:
> On 10 Jan 2006 15:18:22 -0800, [EMAIL PROTECTED] wrote:
>> I want to be able to pass a sequence (tuple, or list) of objects to a
>> function, or only one.
>
...
> but in case you're curious, the easiest
> way to tell an iterable from a non-iterable is by trying to iterate over
> it. Actually, by doing what iterating over it /would/ have done:
>
...
You can usefully wrap up this test in a convenience function that always
returns
an iterator (possibly over a zero length sequence):
>>> for i in safe_iter(scalar_or_iterable): #do something
One definition of safe_iter is below. Your definition may depend on the
specific application:
Cheers
Michael
def safe_iter(obj, atomic_types = (basestring, int, float, complex)):
"""Equivalent to iter when obj is iterable and not defined as atomic.
If obj is defined atomic or found to be not iterable, returns iter((obj,)).
safe_iter(None) returns an empty iterator"""
if not isinstance(obj, atomic_types):
try:
return iter(obj)
except TypeError:
pass
return iter((obj,) * (obj is not None))
def test_safe_iter():
assert list(safe_iter(1)) == [1]
assert list(safe_iter("string")) == ["string"]
assert list(safe_iter(range(10))) == range(10)
assert list(safe_iter(xrange(10))) == list(xrange(10))
assert list(safe_iter((1,2,3))) == [1,2,3]
assert list(safe_iter(1.0)) == [1.0]
assert list(safe_iter(1+2j)) == [1+2j]
xiter = iter(range(10))
assert safe_iter(xiter) is xiter
xiter = (a for a in range(10))
assert safe_iter(xiter) is xiter
assert list(safe_iter(None)) == []
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