how can i check whether a variable is iterable in my code?

[satoru]

hi, all
i want to check if a variable is iterable like a list, how can i
implement this?

[Aidan]

Re: how can i check whether a variable is iterable in my code?

satoru wrote:

hi, all
i want to check if a variable is iterable like a list, how can i
implement this?

this would be one way, though I'm sure others exist:

if hasattr(yourVar , '__iter__'):
# do stuff

[satoru]

Re: how can i check whether a variable is iterable in my code?

On Sep 20, 6:35 pm, Aidan <ai...@gmail.co mwrote:

satoru wrote:

hi, all
i want to check if a variable is iterable like a list, how can i
implement this?

>
this would be one way, though I'm sure others exist:
>
if hasattr(yourVar , '__iter__'):
        # do stuff

thank you,but this will miss out sequences like string just because it
doesn't have an attribute named '__iter__'

[Vito De Tullio]

Re: how can i check whether a variable is iterable in my code?

satoru wrote:

hi, all
i want to check if a variable is iterable like a list, how can i
implement this?

untested

def is_iterable(par am):
try:
iter(param)
except TypeError:
return False
else:
return True

--
By ZeD

[John Machin]

Re: how can i check whether a variable is iterable in my code?

On Sep 20, 8:54 pm, satoru <torainLi...@gm ail.comwrote:

On Sep 20, 6:35 pm, Aidan <ai...@gmail.co mwrote:
>

satoru wrote:

hi, all
i want to check if a variable is iterable like a list, how can i
implement this?

>

this would be one way, though I'm sure others exist:

>

if hasattr(yourVar , '__iter__'):
        # do stuff

>
thank you,but this will miss out sequences like string just because it
doesn't have an attribute named '__iter__'

str objects have a __getitem__ attribute, as do other built-in
sequence types: unicode, xrange, buffer.
AFAIK if an object has no __iter__ but has a __getitem__, iter(obj)
will create an iterator that calls obj.__getitem__ (0),
obj.__getitem__ (1), etc until IndexError is raised.

[satoru]

Re: how can i check whether a variable is iterable in my code?

thanks very much!

[Terry Reedy]

Re: how can i check whether a variable is iterable in my code?

satoru wrote:

On Sep 20, 6:35 pm, Aidan <ai...@gmail.co mwrote:

>satoru wrote:

>>hi, all
>>i want to check if a variable is iterable like a list, how can i
>>implement this?

>this would be one way, though I'm sure others exist:
>>
>if hasattr(yourVar , '__iter__'):
> # do stuff

>
thank you,but this will miss out sequences like string just because it
doesn't have an attribute named '__iter__'

In 3.0, it does. Such consistency is one of the advantages of 3.0.

In at least some 2.x's, str still uses the older __getitem__ iteration
protocol. I am not sure about other built-in sequences.

[James Mills]

Re: how can i check whether a variable is iterable in my code?

satoru,

I should point out that the normal
approach is to just try whatever it
is that you're doing, and let it fail
where it fails. For example:

def processSeq(x):
for i in x:
print i

processSeq([1, 2, 3])
processSeq("foo bar")
processSeq(5) <-- This will fail.

cheers
James

On Sat, Sep 20, 2008 at 7:28 PM, satoru <torainLight@gm ail.comwrote:

hi, all
i want to check if a variable is iterable like a list, how can i
implement this?
--

http://mail.python.org/mailman/listinfo/python-list

>

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