Encapsulating conditional execution based on list membership - how do you do it?

[metaperl]

I have a series of scripts which retrieve files. None of these scripts
should continue if the file to be retrieved already exists in the
archive. Here is the code:

if f in path(self.stora ge.archive).fil es('*'):
print f, "exists in archive. Not continuing"
sys.exit()


self.storage is a class which gives me object-oriented access to the
filesystem directories that will be manipulated by the script. E.g.
self.storage.ar chive is a string which refers to a certain directory.
Initializing this object initializes all the members (input, archive,
output, workfiles) and makes all the correct directories.

ok, so I'm thinking of adding a method to the storage class so I can do
this:

self.storage.ar chive_has(f, print_msg=True) and sys.exit()

but really there is no need to hardcode which storage directory. So I'm
thinking:

self.storage.me mberof('archive ', f, print_msg=Tree) and sys.exit()


Is that the best solution you can think of?

[Gabriel Genellina]

Re: Encapsulating conditional execution based on listmembership - how do you do it?

At Monday 11/12/2006 12:23, metaperl wrote:

>ok, so I'm thinking of adding a method to the storage class so I can do
>this:
>
>self.storage.a rchive_has(f, print_msg=True) and sys.exit()
>
>but really there is no need to hardcode which storage directory. So I'm
>thinking:
>
>self.storage.m emberof('archiv e', f, print_msg=Tree) and sys.exit()
>
>
>Is that the best solution you can think of?

This is just _my_ opinion, of course.
I don't like the construct "blablabla( ) and sys.exit()" or
"blablabla( ) or sys.exit()", I prefer an explicit check "if not
blablabla(): exit()"
I'm not sure what you mean by "archive" but instead of a string, make
it an object so you can write self.storage.ar chive.has_file( f). The
check should do just *that*, return a boolean without side effects;
if you want to print a message, make the caller print it.
If you alias .has_file as .__contains__, you could also write: if f
in self.storage.ar chive, which looks even better.


--
Gabriel Genellina
Softlab SRL

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