question about imports in a class

[Diez B. Roggisch]

J schrieb:
> Just a little newbie confusion about OS imports...
> 
> Why does this give me an error:
> 
> class Windows:
> 
>     def __init__(self):
>         '''
>         Constructor
>         '''
>         import os
>         self.dmidecodePath="" #final path to dmidecode binary
> 
>     def parseDMI(self):
>         # First, find dmidecode.exe
> 
>         for root,dirs,files in os.walk('C:\\'):
>             for file in files:
>                 if file == "dmidecode.exe":
> 
> self.dmidecodePath=[os.path.normcase(os.path.join(root,file))]
>                     return "Found DMIDecode.exe at %s" % self.dmidecodePath
>                     break
> 
> Keep in mind that this is very early stage code and does nothing so
> far other than telling me where to find dmidecode.exe...
> 
> But why does importing in the init not make os available to every
> other function in the class?  Do I have to import OS into every
> function like this:
> 
> class ClassA():
> 
>     def func1(self):
>         import os
> 
>     def func2(self):
>         import os


No, you don't have to - you just import it once at the module level.



> Also, when I DO have the import statement inside the function
> definition, I'm screwing up the join and getting this:
> "C:\\dmidecod\\sbin\\dmidecode.exe"
> 
> What am I doing that's creating the two \ characters??

No, you don't screw it up, "\\" is escape-codes for backslash, and I 
guess what you see is because you work in the interactive interpreter 
that calls repr() on a string when it's displayed - like this:

 >>> "\\"
'\\'
 >>> print "\\"
\
 >>> print repr("\\")
'\\'




> 
> Anyway, the first question I'm just asking because I'm still trying to
> figure out the heirarchy and how classes work in Python, the other is
> because I'm just annoyed...
> 
> Also, that brings up a third question:
> 
> So in my class, I import OS.  Now, in my calling script, do I also
> import OS, or will I inheirit OS as part of the class object?

No, it doesn't, and I'd say you better forget about importing inside 
functions (methods or normal ones) until you have firmer grasp on how 
python namespaces work.

> 
> IOW:
> 
> script.py
> 
> thisclass=myclass():  #where myclass imports os
> 
> for r,d,f in os.walk(path)
> 
> or would I have to do something like:
> 
> for r,d,f in thisclass.os.wall(path)
> 
> Or do I just have to also import OS into script.py??

Yes, you do.


Diez