[optparse] Problem with getting an option value

[Lucas Malor]

Hello all. I'm trying to do a little script. Simply I want to make a list of all options with them default values. If the option is not specified in the command line, the script must try to read it in a config.ini file. If it's not present also there, it must set the default value.

The problem is I maked a simple list for this:

optname = [
[ "delete", False ],
[ "file", "file" ],
[ "dir", "" ],

But I must check that the option was specified in command line:

(options, args) = parser.parse_args()
for opt in optname :
if not options.opt[0] :
# read the options from config.ini

The problem is options is an instance, so options."delete", for example, is wrong; I should pass options.delete . How can I do?

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[Peter Otten]

Lucas Malor wrote:

Hello all. I'm trying to do a little script. Simply I want to make a list
of all options with them default values. If the option is not specified in
the command line, the script must try to read it in a config.ini file. If
it's not present also there, it must set the default value.

The problem is I maked a simple list for this:

optname = [
[ "delete", False ],
[ "file", "file" ],
[ "dir", "" ],

But I must check that the option was specified in command line:

(options, args) = parser.parse_args()
for opt in optname :
if not options.opt[0] :
# read the options from config.ini

The problem is options is an instance, so options."delete", for example,
is wrong; I should pass options.delete . How can I do?

Use getattr():

for name, default_value in optname:
if getattr(options, name) == default_value:
value = ... # read value from config file
setattr(options, name, value)

Personally, I would always read the config file, use the values found there
to set up the parser and avoid such post-processing.

Peter

[Mel Wilson]

Peter Otten wrote:

Lucas Malor wrote:

>Hello all. I'm trying to do a little script. Simply I want to make a list
of all options with them default values. If the option is not specified in
the command line, the script must try to read it in a config.ini file. If
it's not present also there, it must set the default value.

The problem is I maked a simple list for this:

optname = [
[ "delete", False ],
[ "file", "file" ],
[ "dir", "" ],

But I must check that the option was specified in command line:

(options, args) = parser.parse_args()
for opt in optname :
if not options.opt[0] :
# read the options from config.ini

The problem is options is an instance, so options."delete", for example,
is wrong; I should pass options.delete . How can I do?

Use getattr():

for name, default_value in optname:
if getattr(options, name) == default_value:
value = ... # read value from config file
setattr(options, name, value)

Personally, I would always read the config file, use the values found there
to set up the parser and avoid such post-proc

But then, if the command-line value == the default_value the program
will try to get a value from the config file. If the config file
overrides the defaults, then the command line can't re-override.

Stuck with this, I usually initialize with None, then after all the
option sources have been done, set anything that's still None to the
default. It's not tidy.

If even None could be a valid value, then a new None:

class LikeNothingElse:
'''Not a reasonable option value for anything'''
# ... various code
option_a = LikeNothingElse
option_b = LikeNothingElse
# ... process all the option sources
if option_a == LikeNothingElse:
option_a = None
Mel.