I am new to argparser in python . I am trying to create argparser for file which contains two functions download and upload file on/from box. It will do only one functionality at once according according to that i am trying to create parser for that file as follows but it's not working for me:
parser = argparse.ArgumentParser(description='Download or Upload file on box.')
parser.add_argument('-df', '--download', required=True,
help='download file box')
parser.add_argument('-uf', '--upload', nargs='+', required=True,
help='upload file of box')
parser.add_argument('-fp', '--filepath', required=True,
help='file path to upload(which file to upload) or download(where to download file)')
parser.add_argument('-fn', '--filename', required=True,
help='what should be the name of file on box')
parser.add_argument('-fi', '--fileid', required=True,
help='file id of file to download from box')
args = vars(parser.parse_args())
NOTE :- every time only -df or -uf options will be there, -fp is mandatory for both and if it is -df then -fi is only option and it is mandatory and if -uf then -fn is only option and it's mandatory.
How do I achieve this, following are example how will i pass argument to file
pyhton abc.py -df -fp 'Download/boxfile/xyz.txt' -fi 123
python abc.py -uf -fp 'Download/boxfile/xyz.txt' -fn 'qwe.txt'
As written all 5 of the arguments are required - you made that explicit. If that's what you really want, all the rest of the question is irrelevant. You'll have to provide all 5 regardless.
But the comments indicate that you want to use either -df or -uf, but probably not both (though that bit's unclear).
While there is a mutually_exclusive_mechanism in argparse, there isn't a inclusive equivalent - something that says if -f is present, then -g must also be given.
But subparsers mechanism can be used that way. You could define an download subparser, with a required -fi argument. And an upload with its own argument.
Another option is to set -df to take 2 arguments (nargs=2), both its box and its file.
If -df and -uf are mutually exclusive, why not use the same argument for the name of the file? That is, replace -fn and -fi with one file argument.
Another option is to make all (or most) of the arguments not-required, and check for the correct combinations after parsing. It's easier to implement complicated logic in your own code than to force argparse to do it for you.
e.g.
if args.download is not None: # not default
<check for `args.filename`> etc
It can also be a good idea to provide defaults for optional arguments. That way the code can run even if the user doesn't provide all items.
On a matter of style. Short option flags, with on - are usually a single character. -d, -u, etc. The ability to combine several into one string only works in that case, e.g. -df foo. In this case it probably doesn't matter since none of your arguments are store_true.
I'm not incredibly familiar with argparse, however from reading the documentation I don't believe there's a way to use mutually_exclusive_group and required to force this. It seems conditional statements or equivalent are necessary to confirm that valid parameter combinations were passed.
See: Python Argparse conditionally required arguments
I'd suggest that you get rid of most of these arguments, maybe all, and think about standard Unix ways of doing things.
Consider scp, which has a syntax of: scp source destination
For instance: scp Download/boxfile/xyz.txt qwe.txt
If you don't supply a destination, it infers that you want the file to be called the same thing, and land right here, so these two things are equivalent:
scp Download/boxfile/xyz.txt xyz.txt
scp Download/boxfile/xyz.txt
Of course, scp can talk to machines across the internet, so there is a format for that:
scp hostname:Download/boxfile/xyz.txt xyz.txt
And if you are uploading, you simple switch the order:
scp xyz.txt hostname:Download/boxfile/xyz.txt
Related
I'm trying to build a program that takes the first argument as an action (like program list, program create, program delete, etc.), and then uses the rest of the provided options in context to the action (like -c, --all, etc.).
How can I define the same optional argument several times, for each action I define in the first argument?
#hpaulj's comment helped me solve this. I've used subparsers and created separated contexts to store a config for each main action that I have in my script.
An example can be found here: https://stackoverflow.com/a/53324772/901925
You can use something like this:
parser = argparse.ArgumentParser()
parser.add_argument("action", type=str, help="action like create or delete")
parser.add_argument("-c", action="count", default=0)
in this case, the first argument given without -c will be stored in action variable.
using argparse:
parser.add_argument("-o", "--output", help="Log to file")
I want to achieve the following behavior:
The user doesn't specify the -o flag - no logging should be done.
User specifies the -o with nothing - I should log to a default location,
defined within my program.
User specifies -o and a string(path) - I should log there.
Does anyone know the best way to use add_argument to achieve that? I saw a similar example with int values, but in my case, it doesn't get my default value.
You can use nargs='?' for this:
parser.add_argument('-o', '--output',
nargs='?', default=None, const='my_default_location')
If not present, it will produce the default value, if present but without a value it'll use const, otherwise it'll use the supplied value.
Also read through the other examples in the docs, there's a sample for an optional output file which could be useful.
I have a python script that I'd like to supply with an argument (usually) containing wildcards, referring to a series of files that I'd like to do stuff with. Example here:
#!/usr/bin/env python
import argparse
import glob
parser = argparse.ArgumentParser()
parser.add_argument('-i', action="store", dest="i")
results = parser.parse_args()
print 'argument i is: ', results.i
list_of_matched_files = glob.glob(results.i)
In this case, everything works great if the user adds quotes to the passed argument like so:
./test_script.py -i "foo*.txt"
...but often times the users forget to add quotes to the argument and are stumped when the list only contains the first match because UNIX already expanded the list and argparse only then gets the first list element.
Is there a way (within the script) to prevent UNIX from expanding the list before passing it to python? Or maybe even just to test if the argument doesn't contain quotes and then warn the user?
No. Wildcards are expanded by the shell (Bash, zsh, csh, fish, whatever) before the script even runs, and the script can't do anything about them. Testing whether the argument contains quotes also won't work, as the shell similarly strips the quotes from "foo*.txt" before passing the argument to the script, so all Python sees is foo*.txt.
Its not UNIX that is doing the expansion, it is the shell.
Bash has an option set -o noglob (or -f) which turns off globbing (filename expansion), but that is non-standard.
If you give an end-user access to the command-line then they really should know about quoting. For example, the commonly used find command has a -name parameter which can take glob constructs but they have to be quoted in a similar manner. Your program is no different to any other.
If users can't handle that then maybe you should give them a different interface. You could go to the extreme of writing a GUI or a web/HTML front-end, but that's probably over the top.
Or why not prompt for the filename pattern? You could, for example, use a -p option to indicate prompting, e.g:
import argparse
import glob
parser = argparse.ArgumentParser()
parser.add_argument('-i', action="store", dest="i")
parser.add_argument('-p', action="store_true", default=False)
results = parser.parse_args()
if results.p:
pattern = raw_input("Enter filename pattern: ")
else:
pattern = results.i
list_of_matched_files = glob.glob(pattern)
print list_of_matched_files
(I have assumed Python 2 because of your print statement)
Here the input is not read by the shell but by python, which will not expand glob constructs unless you ask it to.
You can disable the expansion using set -f from the command line. (re-enable with set +f).
As jwodder correctly says though, this happens before the script is run, so the only way I can think of to do this is to wrap it with a shell script that disables expansion temporarily, runs the python script, and re-enables expansion. Preventing UNIX from expanding the list before passing it to python is not possible.
Here is an example for the Bash shell that shows what #Tom Wyllie is talking about:
alias sea='set -f; search_function'
search_function() { perl /home/scripts/search.pl $# ; set +f; }
This defines an alias called "sea" that:
Turns off expansion ("set -f")
Runs the search_function function which is a perl script
Turns expansion back on ("set +f")
The problem with this is that if a user stops execution with ^C or some such then the expansion may not be turned back on leaving the user puzzling why "ls *" is not working. So I'm not necessarily advocating using this. :).
This worked for me:
files = sys.argv[1:]
Even though only one string is on the command line, the shell expands the wildcards and fills sys.argv[] with the list.
I want to use the argparser module with multiple command-line and some of them should have no arguments.
Example:
parser.add_argument('-website', type=str, nargs='*')
parser.add_argument('-auth', type=str, nargs='*')
parser.add_argument('-dothis', action='store_true')
So I want to call in a command line following commands:
- python script.py -website www.website.com www.website2.com -dothis
In this case the -dothis command should only be use for the second website not for the first one, but it is used for both websites.
Another example:
-python script.py -website www.website1.com www.website2.com -auth username/password
In this case the second website has a authentication not the first one.
So what I want is:
- python script.py www.webstie1.com -dothis www.website2.com -auth u:p -dothis www.website3.com -auth u:p www.website4.com
or:
- python script.py -site www.website1.com -auth u:p -site www.website2.com -site www.website3.com -auth u2:p2
so how my script knows which auth is for which website?
How can I fix it?
Your examples are inconsistent. One has '-website' with 2 values, an other has '-site' repeated (append action?), and the third repeated positionals.
Your goal runs into several fundamental issues with argparse:
optionals are parsed in an order independent manner
arguments normally don't interact
usage does not have provision for displaying interactions
I can write a set of custom Action classes that perform the kind of interaction that you want. But are you really interested?
The basic parsing strategy of argparse is to handle the 'positionals' in order, but 'optionals' (flagged) arguments can occur in any order. So the resulting args namespace does not have information about the order of the commands strings. Old parsers like getopt and optparse aren't much better, since they focus on collecting the optionals, and returning the rest as a undifferentiate list.
An alterantive to custom Action classes is to parse sys.argv yourself. Just iterate through the strings. A string without '--' is a site; any '--' flags the follow apply to that site, etc.
A twist on your desired API is to define '--website' as an append that takes multiple arguments.
parser.add_argument('--website','-w','--site',dest='site',nargs='+',action='append',
help='website plus flags; may repeat')
possible commandlines and Namespaces:
--site www.webwsite.com dothig --site www.website2.com
NS(site=[['www.website.con','dothis'],['website2']])
--site site1 username/pass --site site2
NS(site=[['site1','username/pass'],['site2']])
So for each element in args.site, you can interpret the 1st item as the site name, a parse the rest to find the dothis flag and the auth name.
My apology in advance if it's already answered somewhere; I've been in the python site since last hr. but didn't quite figure out how I can I do this. My script should take the options like this:
myScript.py -f <file-name> -e [/ -d]
myScript.py -s <string> -e [/ -d]
myScript.py -f <file-name> [/ -s <string>] -e -w [<file_name>]
i.e. -f/-s,-e/-d are mandatory options but -f&-s cannot be used together and the same as with -e&-d options - cannot be used together. How can I put the check in place?
Another question, if I may ask at the same time: How can I use -w option (when used) with or w/o a value? When no value is supplied, it should take the default value otherwise the supplied one.
Any help greatly appreciated. Cheers!!
It's been a while since I did anything with optparse, but I took a brief look through the docs and an old program.
"-f/-s,-e/-d are mandatory options but -f&-s cannot be used together and the same as with -e&-d options - cannot be used together. How can I put the check in place?"
For mutual exclusivity, you have to do the check yourself, for example:
parser.add_option("-e", help="e desc", dest="e_opt", action="store_true")
parser.add_option("-d", help="d desc", dest="d_opt", action="store_true")
(opts, args) = parser.parse_args()
if (parser.has_option("-e") and parser.has_option("-d")):
print "Error! Found both d and e options. You can't do that!"
sys.exit(1)
Since the example options here are boolean, you could replace the if line above with:
if (opts.e_opt and opts.d_opt):
See the section How optparse handles errors for more.
"How can I use -w option (when used) with or w/o a value?"
I've never figured out a way to have an optparse option for which a value is, well, optional. AFAIK, you have to set the option up to have values or to not have values. The closest I've come is to specify a default value for an option which must have a value. Then that entry doesn't have to be specified on the command line. Sample code :
parser.add_option("-w", help="warning", dest="warn", default=0)
An aside with a (hopefully helpful) suggestion:
If you saw the docs, you did see the part about how "mandatory options" is an oxymoron, right? ;-p Humor aside, you may want to consider re-designing the interface, so that:
Required information isn't entered using an "option".
Only one argument (or group of arguments) enters data which could be mutually exclusive. In other words, instead of "-e" or "-d", have "-e on" or "-e off". If you want something like "-v" for verbose and "-q" for quiet/verbose off, you can store the values into one variable:
parser.add_option("-v", help="verbose on", dest="verbose", action="store_true")
parser.add_option("-q", help="verbose off", dest="verbose", action="store_false")
This particular example is borrowed (with slight expansion) from the section Handling boolean (flag) options. For something like this you might also want to check out the Grouping Options section; I've not used this feature, so won't say more about it.
You should try with argparse if you are using 2.7+.
This section should be what you want.
Tl;dr:
parser = argparse.ArgumentParser()
group = parser.add_mutually_exclusive_group()
group.add_argument('--foo', action='store_true')
group.add_argument('--bar', action='store_false')
makes --foo and --bar mutually exclusive. See detailed argparse usage for more informations on using ArgumentParsers
Remember that optparse is deprecated, so using argparse is a good idea anyway.