detecting variable types

[djw]

Jay wrote:

> Thanks, Peter.
> 
> Here's what I'm trying to do:
> 
> I have a function like this:
> 
> def func(**params):
> 
>     # if params[key1] is a single string
>         # do something with params[key1]
> 
>     # if params[key1] is a list of strings
>         for val in params[key1]:
>             # do something
> 
> Could you suggest a better way to do this without detecting the type?
> 
> 
> Jay.
> 
> 
> "Peter Hansen" <peter at engcorp.com> wrote in message
> news:Y-WdnWCkPIytTszcRVn-vQ at powergate.ca...
>> Jay wrote:
>> > I'm sure this is a really dumb question, but how do you detect a
> variable
>> > type in Python?
>> >
>> > For example, I want to know if the variable "a" is a list of strings or
> a
>> > single string. How do I do this?
>>
>> Use the builtin function "type()", but note the following:
>>
>> 1. Variables don't actually have types in Python (and they're usually
>> called "names" in Python, for various reasons), but the data they are
>> currently bound to does have a type and that's what type() returns.
>> Often the distinction won't matter to you...
>>
>> 2. Most of the time people trying to do what you are probably trying
>> to do are going about things the wrong way, often from experience
>> with other languages.  Lots of Python folks would be happy to introduce
>> you to "better" ways to do things, if you'll explain the use case
>> and tell us what you're actually trying to accomplish.  (Of course,
>> using "type()" will work, but it's rarely considered the best
>> approach in the Python community.)
>>
>> -Peter


One obvious way, in this case is to always pass in a list of strings. A
single string would be passed in as a list with a single string item in it.

def func( stringlist ):
        for s in stringlist:
                #do something with s

func( [ "single string" ] )
func( [ "more", "than", "one", "string" ] )

Other than that, if the functions are really doing something very different
given different parameter types, then I would make separate functions.

-Don