passing arguments

[Jeff Elkins]

I'm sure this is obvious, but how the heck do pass an argument(s) to a python
script from the command line?

Thanks,

Jeff Elkins

[James Stroud]

import sys

try:
arg1 = sys.argv[1]
except IndexError:
print "This script takes an argument, you boob!"
sys.exit(1)

OR, way better: See the optparse module.

--
James Stroud
UCLA-DOE Institute for Genomics and Proteomics
Box 951570
Los Angeles, CA 90095

http://www.jamesstroud.com/

[Jeff Elkins]

On Friday 20 May 2005 06:46 pm, James Stroud wrote:
> import sys
>
> try:
> arg1 = sys.argv[1]
> except IndexError:
> print "This script takes an argument, you boob!"
> sys.exit(1)
>
> OR, way better: See the optparse module.
>
> On Friday 20 May 2005 03:26 pm, Jeff Elkins wrote:
> > I'm sure this is obvious, but how the heck do pass an argument(s) to a
> > python script from the command line?
> >
> > Thanks,
> >
> > Jeff Elkins

Thanks!

[Steven Bethard]

James Stroud wrote:
> import sys
>
> try:
> arg1 = sys.argv[1]
> except IndexError:
> print "This script takes an argument, you boob!"
> sys.exit(1)

Also possible, to guarantee that exactly one argument was given:

try:
arg1, = sys.argv
except ValueError:

print "This script takes an argument, you boob!"
sys.exit(1)

If you want to get, say, 3 arguments, just change that line to:

arg1, arg2, arg3 = sys.argv

> OR, way better: See the optparse module.

Definitely. Though depending on what kind of arguments your script
takes, you still may need to deal with the args that optparse returns.

STeVe

[Philippe C. Martin]

Hi,

look at sys.argv

Regards,

Philippe

[Steve Holden]

Steven Bethard wrote:
> James Stroud wrote:
>
>>import sys
>>
>>try:
>> arg1 = sys.argv[1]
>>except IndexError:
>> print "This script takes an argument, you boob!"
>> sys.exit(1)
>
>
> Also possible, to guarantee that exactly one argument was given:
>
> try:
> arg1, = sys.argv
> except ValueError:
> print "This script takes an argument, you boob!"
> sys.exit(1)
>

Aren't we forgetting argv[0] here, or am I overlooking something (like,
you chopped it off without telling me?)?

Surely this would give an unpacking error if command-line arguments
*were* present.

> If you want to get, say, 3 arguments, just change that line to:
>
> arg1, arg2, arg3 = sys.argv
>

Similarly. Or are you just calling sys.argv[0] arg1 to confuse me? ;-)

>
>>OR, way better: See the optparse module.
>
>
> Definitely. Though depending on what kind of arguments your script
> takes, you still may need to deal with the args that optparse returns.
>

Anyway it's always good to know about the underlying mechanisms.

regards
Steve
--
Steve Holden +1 703 861 4237 +1 800 494 3119
Holden Web LLC http://www.holdenweb.com/
Python Web Programming http://pydish.holdenweb.com/

[Steve Holden]

Dennis Lee Bieber wrote:
> On Sun, 22 May 2005 16:12:06 -0400, Steve Holden <st...@holdenweb.com>
> declaimed the following in comp.lang.python:

>
>
>
>>Aren't we forgetting argv[0] here, or am I overlooking something (like,
>>you chopped it off without telling me?)?
>>
>

> argv[0] is often just the invocation name of the program/script
> itself, not really an argument to the function of the program.
>
And you think I don't know this? I was questioning the correctness of
the assertions of the post to which I was replying. Whether it's a real
argument or not in undoubtedly occupies an entry in sys.argv.

> script1.py
> -=-=-=-=-=-=-=-=-
> import sys
>
> for x in range(len(sys.argv)):
> print "Argument %s is %s" % (x, sys.argv[x])
> -=-=-=-=-=-=-=-=-
>
> (watch out for line wrapping)
>
> E:\UserData\Dennis Lee Bieber\My Documents>script1.py "These are the"
> Voyages
> Argument 0 is E:\UserData\Dennis Lee Bieber\My Documents\Script1.py
> Argument 1 is These are the
> Argument 2 is Voyages
>
> E:\UserData\Dennis Lee Bieber\My Documents>python script1.py "quoted
> arg" regular args
> Argument 0 is script1.py
> Argument 1 is quoted arg
> Argument 2 is regular
> Argument 3 is args
>
> E:\UserData\Dennis Lee Bieber\My Documents>
>
>
So?

[Steven Bethard]

Steve Holden wrote:

> Steven Bethard wrote:
>>
>> Also possible, to guarantee that exactly one argument was given:
>>
>> try:
>> arg1, = sys.argv
>> except ValueError:
>> print "This script takes an argument, you boob!"
>> sys.exit(1)
>>
> Aren't we forgetting argv[0] here

Oops. Yup. Change all "sys.argv" to "sys.argv[1:]". Sorry, I never
use sys.argv directly anymore; I always get my argv through optparse,
which kindly strips off sys.argv[0]. Good catch, thanks!

STeVe