|  | Check if module is installed | | |
| | | Kless |  |
|  Posted: Mon Aug 04, 2008 12:25 pm Post subject: Check if module is installed |  |
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
-------------------
Thanks in advance! |
| |
| | | Chris Ortner | |
| | Posted: Mon Aug 04, 2008 12:57 pm Post subject: Re: Check if module is installed | |
On Aug 4, 2:25 pm, Kless <jonas....@googlemail.com> wrote:
| Quote: | try:
import foo
foo_loaded = True
except ImportError:
foo_loaded = False
|
Many projects use this as the standard procedure to check a module's
presence. I assume, this is the best way.
Chris |
| |
| | | Steven D'Aprano | |
| | Posted: Mon Aug 04, 2008 9:12 pm Post subject: Re: Check if module is installed | |
| |  | |
On Mon, 04 Aug 2008 05:25:08 -0700, Kless wrote:
| Quote: | 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 |
| |
| | | Wojtek Walczak | |
| | Posted: Mon Aug 04, 2008 9:54 pm Post subject: Re: Check if module is installed | |
Dnia Mon, 4 Aug 2008 05:25:08 -0700 (PDT), Kless napisa³(a):
| Quote: | 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.
|
You may also be interested in techniques to keep your software
compatible with older versions of python. Take a look at this
example: LINK
--
Regards,
Wojtek Walczak,
LINK |
| |
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