An optparse question

[T]

I have a short program using optparse.OptionParser that prints out help
message with -h flag:

% myprog.py -h
usage: myprog.py [options] input_file

options:
-h, --help show this help message and exit
-v, --verbose print program's version number and exit
-o FILE Output file


My question is, is there a way to print a blank line (or any string)
before "usage: myprog.py [options] input_file" ? I tried using
callbacks without success. I think somehow I need to modify the
behavior of optparse.OptionParser.print_usage() function?

 

[fuzzylollipop]

I have a short program using optparse.OptionParser that prints out help
message with -h flag:

% myprog.py -h
usage: myprog.py [options] input_file

options:
-h, --help show this help message and exit
-v, --verbose print program's version number and exit
-o FILE Output file


My question is, is there a way to print a blank line (or any string)
before "usage: myprog.py [options] input_file" ? I tried using
callbacks without success. I think somehow I need to modify the
behavior of optparse.OptionParser.print_usage() function?

you can make the usage line anything you want.

....
usage = 'This is a line before the usage line\nusage %prog [options]
input_file'
parser = OptionsParser(usage=usage)
parser.print_help()
....

 

[T]

you can make the usage line anything you want.

...
usage = 'This is a line before the usage line\nusage %prog [options]
input_file'
parser = OptionsParser(usage=usage)
parser.print_help()
...

No, that affects the string printed only *after* the "usage = " string.
What I would like to do is insert some string *before* the "usage = "
string, which is right after the command I type at the command prompt.
So I would like to make it look like this:

% myprog.py -h
************ THIS IS NEWLY INSERTED STRING ************
usage: myprog.py [options] input_file


options:
-h, --help show this help message and exit
-v, --verbose print program's version number and exit
-o FILE Output file

 

[dan.gass]

No, that affects the string printed only *after* the "usage = " string.

What I would like to do is insert some string *before* the "usage = "
string, which is right after the command I type at the command prompt.
So I would like to make it look like this:

The example was fine (except for a typo) as far as demonstrating the
concept. Try this corrected version:

from optparse import OptionParser

usage = '************ THIS IS NEWLY INSERTED STRING
************\nusage: %prog [options] input_file'
parser = OptionParser(usage=usage)
parser.print_help()

 

[Simon Forman]

you can make the usage line anything you want.

...
usage = 'This is a line before the usage line\nusage %prog [options]
input_file'
parser = OptionsParser(usage=usage)
parser.print_help()
...

No, that affects the string printed only *after* the "usage = " string.
What I would like to do is insert some string *before* the "usage = "
string, which is right after the command I type at the command prompt.
So I would like to make it look like this:

% myprog.py -h
************ THIS IS NEWLY INSERTED STRING ************
usage: myprog.py [options] input_file


options:
-h, --help show this help message and exit
-v, --verbose print program's version number and exit
-o FILE Output file

It's possible, but it ain't easy:

from optparse import OptionParser, _, IndentedHelpFormatter

class MyFormatter(IndentedHelpFormatter):
pre_usage = "Hi there!\n"
def format_usage(self, usage):
return _("%susage: %s\n") % (self.pre_usage, usage)

parser = OptionParser(formatter=MyFormatter())


The above filthy hack will print "Hi there!" before the usual usage
message.

 

[Simon Forman]

No, that affects the string printed only *after* the "usage = " string.
What I would like to do is insert some string *before* the "usage = "
string, which is right after the command I type at the command prompt.
So I would like to make it look like this:

The example was fine (except for a typo) as far as demonstrating the
concept. Try this corrected version:

from optparse import OptionParser

usage = '************ THIS IS NEWLY INSERTED STRING
************\nusage: %prog [options] input_file'
parser = OptionParser(usage=usage)
parser.print_help()

Nope. That only *nearly* does what T wants. The usage message will
still be printed immediately *after* the 'usage: ' string.
usage: ************ THIS IS NEWLY INSERTED STRING************
usage: lopts.py [options] input_file

options:
-h, --help show this help message and exit


I had the same problem, and in order to get something printed before
the usage message, I found one easy-ish way was to subclass the
Formatter passed in to the Parser.

IMHO, optparse does a tricky task well, but it's implemented in a hard
to follow, inflexible manner. My "favorite" pet peeve is that the
options "dictionary" it returns isn't a dict. I wound up doing this to
it to get something [I considered] useful:

o, a = parser.parse_args()
o = o.__dict__.copy()


Peace,
~Simon

 

[Steve Holden]

you can make the usage line anything you want.

...
usage = 'This is a line before the usage line\nusage %prog [options]
input_file'
parser = OptionsParser(usage=usage)
parser.print_help()
...

No, that affects the string printed only *after* the "usage = " string.
What I would like to do is insert some string *before* the "usage = "
string, which is right after the command I type at the command prompt.
So I would like to make it look like this:

% myprog.py -h
************ THIS IS NEWLY INSERTED STRING ************
usage: myprog.py [options] input_file


options:
-h, --help show this help message and exit
-v, --verbose print program's version number and exit
-o FILE Output file

Do a Google search for "monkey patching". You probably want to
monkey-patch the class's usage method.

regards
Steve

 

[dan.gass]

Nope. That only *nearly* does what T wants. The usage message will
still be printed immediately *after* the 'usage: ' string.
usage: ************ THIS IS NEWLY INSERTED STRING************
usage: lopts.py [options] input_file

options:
-h, --help show this help message and exit

Yes, I see what T meant now. Behavior expectations (assumptions) has a
way of clouding one's vision.

Thanks

 

[John J. Lee]

What I would like to do is insert some string *before* the "usage = "
string, which is right after the command I type at the command prompt.
So I would like to make it look like this:

% myprog.py -h
************ THIS IS NEWLY INSERTED STRING ************
usage: myprog.py [options] input_file


options:
-h, --help show this help message and exit
-v, --verbose print program's version number and exit
-o FILE Output file

HelpFormatter is what you need. Seems undocumented in the official
docs, but doesn't look risky to use (famous last words). Seems just
that nobody got around to documenting it.

import optparse

class NonstandardHelpFormatter(optparse.HelpFormatter):

def __init__(self,
indent_increment=2,
max_help_position=24,
width=None,
short_first=1):
optparse.HelpFormatter.__init__(
self, indent_increment, max_help_position, width, short_first)

def format_usage(self, usage):
return "************ THIS IS NEWLY INSERTED STRING ************\nusage: %s\n" % usage

def format_heading(self, heading):
return "%*s%s:\n" % (self.current_indent, "", heading)

parser = optparse.OptionParser(
usage="%prog [options] input_file",
formatter=NonstandardHelpFormatter())
parser.parse_args()


John