On Mon, 04 Aug 2008 05:25:08 -0700, Kless wrote:
> How to check is a library/module is installed on the system? I use the
> next code but it's possivle that there is a best way.
>
> -------------------
> try:
> import foo
> foo_loaded = True
> except ImportError:
> foo_loaded = False
> -------------------
The "best" way depends on what you expect to do if the module can't be
imported. What's the purpose of foo_loaded? If you want to know whether
foo exists, then you can do this:
try:
foo
except NameError:
print "foo doesn't exist"
Alternatively:
try:
import foo
except ImportError:
foo = None
x = "something"
if foo:
y = foo.function(x)
If the module is required, and you can't do without it, then just fail
gracefully when it's not available:
import foo # fails gracefully with a traceback
Since you can't continue without foo, you might as well not even try. If
you need something more complicated:
try:
import foo
except ImportError:
log(module not found)
print "FAIL!!!"
sys.exit(1)
# any other exception is an unexpected error and
# will fail with a traceback
Here's a related technique:
try:
from module import parrot # fast version
except ImportError:
# fallback to slow version
def parrot(s='pining for the fjords'):
return "It's not dead, it's %s." % s
--
Steven
--
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