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RE: How to check if a string is empty in python?

 
 
Hamilton, William
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      05-04-2007
> -----Original Message-----
> From: http://www.velocityreviews.com/forums/(E-Mail Removed)
>
> On May 4, 5:02 am, Jaswant <(E-Mail Removed)> wrote:
> > This is a simple way to do it i think
> >
> > s=hello
> >
> > >>> if(len(s)==0):

> >
> > ... print "Empty"
> > ... else:
> > ... print s
> > ...
> > hello

>
> But you are still making the assumption that s is a string.
> (BTW, you need quotes around your example.)
>
> For example:
>
> >>> print a,b

> 11 11
>
> Can you tell which one is the string? I.e., which one had quotes
> around it?
>
> If you correctly assume that it was b, then yes, your example works.
>
> >>> print len(b)

> 2
>
> If you incorrectly assume it was a, then the example doesn't work.
>
> >>> print len(a)

> Traceback (most recent call last):
> File "<pyshell#8>", line 1, in <module>
> print len(a)
> TypeError: object of type 'int' has no len()
>
> You have to know that a variable is a string before you try to do a
> len().
>
> Dynamic typing is a feature, but that doesn't relieve you of the
> necessary tests.


Your point would be important if the question were "How can I tell if x
is an empty string?" On the other hand, "How to check if a string is
empty?" implies that the OP already knows it is a string. Maybe he's
been using string methods on it, maybe he got it from a function that he
knows provides a string. Maybe he's checked its type. It doesn't really
matter, if he's aware it is a string he doesn't have to test it for
stringness.


---
-Bill Hamilton
 
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