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Python Library Reference |  |
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The various option actions all have slightly different requirements and effects. Most actions have several relevant option attributes which you may specify to guide optparse's behaviour; a few have required attributes, which you must specify for any option using that action.
store [relevant: type, dest, nargs, choices]
The option must be followed by an argument, which is
converted to a value according to type and stored in
dest. If nargs > 1, multiple arguments will be consumed
from the command line; all will be converted according to
type and stored to dest as a tuple. See the ``Option
types'' section below.
If choices is supplied (a list or tuple of strings), the type
defaults to choice.
If type is not supplied, it defaults to string.
If dest is not supplied, optparse derives a destination from the
first long option string (e.g., "-foo-bar" implies foo_bar).
If there are no long option strings, optparse derives a destination from
the first short option string (e.g., "-f" implies f).
Example:
parser.add_option("-f")
parser.add_option("-p", type="float", nargs=3, dest="point")
As it parses the command line
-f foo.txt -p 1 -3.5 4 -fbar.txt
optparse will set
options.f = "foo.txt" options.point = (1.0, -3.5, 4.0) options.f = "bar.txt"
store_const [required: const; relevant: dest]
The value const is stored in dest.
Example:
parser.add_option("-q", "--quiet",
action="store_const", const=0, dest="verbose")
parser.add_option("-v", "--verbose",
action="store_const", const=1, dest="verbose")
parser.add_option("--noisy",
action="store_const", const=2, dest="verbose")
If "-noisy" is seen, optparse will set
options.verbose = 2
store_true [relevant: dest]
A special case of store_const that stores a true value
to dest.
store_false [relevant: dest]
Like store_true, but stores a false value.
Example:
parser.add_option("--clobber", action="store_true", dest="clobber")
parser.add_option("--no-clobber", action="store_false", dest="clobber")
append [relevant: type, dest, nargs, choices]
The option must be followed by an argument, which is appended to the
list in dest. If no default value for dest is supplied, an
empty list is automatically created when optparse first encounters this
option on the command-line. If nargs > 1, multiple arguments are
consumed, and a tuple of length nargs is appended to dest.
The defaults for type and dest are the same as for the
store action.
Example:
parser.add_option("-t", "--tracks", action="append", type="int")
If "-t3" is seen on the command-line, optparse does the equivalent of:
options.tracks = []
options.tracks.append(int("3"))
If, a little later on, "-tracks=4" is seen, it does:
options.tracks.append(int("4"))
append_const [required: const; relevant: dest]
Like store_const, but the value const is appended to dest;
as with append, dest defaults to None, and an an empty list is
automatically created the first time the option is encountered.
count [relevant: dest]
Increment the integer stored at dest. If no default value is supplied, dest is set to zero before being incremented the first time.
Example:
parser.add_option("-v", action="count", dest="verbosity")
The first time "-v" is seen on the command line, optparse does the
equivalent of:
options.verbosity = 0 options.verbosity += 1
Every subsequent occurrence of "-v" results in
options.verbosity += 1
callback [required: callback;
relevant: type, nargs, callback_args, callback_kwargs]
Call the function specified by callback, which is called as
func(option, opt_str, value, parser, *args, **kwargs)
See section 14.3.4, Option Callbacks for more detail.
Prints a complete help message for all the options in the
current option parser. The help message is constructed from
the usage string passed to OptionParser's constructor and
the help string passed to every option.
If no help string is supplied for an option, it will still be
listed in the help message. To omit an option entirely, use
the special value optparse.SUPPRESS_HELP.
optparse automatically adds a help option to all OptionParsers, so you do not normally need to create one.
Example:
from optparse import OptionParser, SUPPRESS_HELP
parser = OptionParser()
parser.add_option("-h", "--help", action="help"),
parser.add_option("-v", action="store_true", dest="verbose",
help="Be moderately verbose")
parser.add_option("--file", dest="filename",
help="Input file to read data from"),
parser.add_option("--secret", help=SUPPRESS_HELP)
If optparse sees either "-h" or "-help" on the command line, it
will print something like the following help message to stdout
(assuming sys.argv[0] is "foo.py"):
usage: foo.py [options] options: -h, --help Show this help message and exit -v Be moderately verbose --file=FILENAME Input file to read data from
After printing the help message, optparse terminates your process
with sys.exit(0).
version
Prints the version number supplied to the OptionParser to stdout and
exits. The version number is actually formatted and printed by the
print_version() method of OptionParser. Generally only relevant
if the version argument is supplied to the OptionParser
constructor. As with help options, you will rarely create
version options, since optparse automatically adds them when needed.
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Python Library Reference | |
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