Single string vs list of strings

[Scott Sharkey]

Hi All,

I have a need to determine whether a passed variable is a single string,
or a list of strings. What is the most pythonic way to do this?

Thanks.
-Scott

[Grant Edwards]

Re: Single string vs list of strings

On 2008-10-30, Scott Sharkey <ssharkey@linux unlimited.comwr ote:

I have a need to determine whether a passed variable is a single string,
or a list of strings. What is the most pythonic way to do this?

>>type('asdf' ) is list

False

>>type(['asdf','qwer']) is list

True

The question you might want to asked is whether the parameter
is a single string or a sequence of strings. That way your
code will also work with an iterator that returns strings.

>>type('asdf' ) is str

True

Checking to see if something is a sequence of strings is a bit
trickier, since a string is actually a sequence of strings.
You first have to verify that it's not a string, and then check
for the API that you're going to use (iteration or indexing).

--
Grant Edwards grante Yow! I represent a
at sardine!!
visi.com

[Joe Strout]

Re: Single string vs list of strings

On Oct 30, 2008, at 8:55 AM, Grant Edwards wrote:

The question you might want to asked is whether the parameter
is a single string or a sequence of strings. That way your
code will also work with an iterator that returns strings.
>

>>>type('asdf ') is str

True

I agree with the general approach, but this test will fail for Unicode
strings, and so is probably bad mojo moving forward. Instead I suggest:

isinstance(x, basestring)

which will work whether x='asdf' or x=u'asdf'.

Best,
- Joe

[greg]

Re: Single string vs list of strings

Grant Edwards wrote:

Checking to see if something is a sequence of strings is a bit
trickier, since a string is actually a sequence of strings.

For that reason I'd just check whether it's a string,
and if it's anything else, assume it's a sequence of
strings. You'll find out soon enough if it doesn't
support indexing or iterating or whatever you want to
do with it.

--
Greg