[Tutor] Query about getattr used as a dispatcher

[Chris Calloway]

raghu raghu wrote:
> Actually i installed python 2.5 i ran this script and its showing error 
> it could not import statsout. why is it so?

statsout is a *hypothetical* module used for an example only. The 
statsout module does not actually exist. When Dive Into Python wants you 
to type in an example, it will shown either as lines at the Python 
interpreter prompt (>>>), or it will be an example in a Python source 
file included with the Dive Into Python examples bundle. If you look at 
the example using the imaginary statsout module in section 4.12, which 
is not included in any Python source file in the Dive Into Python 
examples bundle, you will see the example is not referenced in a file, 
nor is it shown as being typed at the Python interpreter prompt.

If, however, you had an actual statsout module in your sys.path, you 
could import it. And it that module had top level functions functions 
that took one argument and had function names like "output_text" and 
"output_pdf" and "output_html," then the example would work if you typed 
it in. The example is just showing a hypothetical case of a very simple 
dispatcher. The example is asking you to imagine *if* you had a statsout 
module, and *if* that module had functions by those names in it.

Dive Into Python uses the getattr function in the apihelper.py example 
you are currently reading about. In the next chapter, a more complicated 
example is shown where getattr is used in a dispatcher which finds, not 
just a function by name, but a class by name and dispatches that class 
object to create a new object of that class. So the statsout *imaginary* 
example is just preparing you for a more complicated *real life* 
dispatcher example in the next chapter. Hypothetical examples are often 
shown in programming books to prepare you for more complicated real life 
examples.

-- 
Sincerely,

Chris Calloway
http://www.seacoos.org
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