How to parse AND store arguments in python?

Question

Currently I am using argparse for parsing arguments in this fashion :

outputFile = ""
input

def getArguments():
    parser = argparse.ArgumentParser(description='Execute the given pig script and pipe the output to given  outFile.')
    parser.add_argument('-o','--outputFile', help='Output file where pig file execution output is stored.', required=True)
    input = parser.parse_args()
    print ("========================================")
    print ("Argument to the script")
    print ("outputFile = %s" % input.outputFile )
    return input
input = getArguments()
outputFile = input.outputFile
print ("outputFile = %s" % outputFile )

My question is, is there a way a better AND/OR more compact way of writing parsing in this way ?

Note : I am especially trying to look for binding of parsed argument to the variable in the file. I hope to not to use "input" variable every-time I access input-argument nor do I want to have explicit variable declared just to copy the parameters from the argument-string to a variable.

@MartijnPieters : Sorry there was a typo when copy pasting. I am returning input. AND then there are bunch of lines doing essentially the following arg1 = input.arg1 — Ajeet Ganga, Sep 20 '13 at 21:39
As a representative of the Pig related tags, Hey! It seems like you are doing this for a python wrapper. Feel free to open a more specific question in `Pig`, we need more questions on this topic. — mr2ert, Sep 20 '13 at 21:40
@Ajeet: But what is wrong with `options.arg1`? There is no need to re-assign all the options to locals here. There is no real advantage to doing so. — Martijn Pieters, Sep 20 '13 at 21:40
Nothing wrong in options.arg1 I want to use arg1 instead :options.arg1 — Ajeet Ganga, Sep 20 '13 at 21:41

score 0 · Answer 1 · edited May 23 '17 at 10:25

As @MartijinPieters points out in the comments, there is nothing wrong with options.arg1. Firstly, I want to echo this. There isn't a very clean (or clear IMHO) way of doing what you are asking for.

What you'll need to do is convert the options object into a dictionary. This can be done using vars:

opt_dict = vars(parser.parse_args())

Then you'll have to load all the values in the dictionary into the locals. I found this question that shows examples of how to do this. I like Ken's answer for its clarity:

for item in opt_dict.iteritems():
    eval('{0} = {1}'.format(*item))

But it allows for the possibility of dangerous input sneaking in. Also, this will have to be done outside of the getArguments() function.

However, I agree that the accepted answer on the previously linked question is probably the best way of doing this, which is to use the opt_dict to update globals.

NOTE: If you are doing this for a Pig python wrapper, like I suspect, then loading the the variables into the locals will actually be counter productive. The variables need to be passed into bind as a dictionary.

Using `eval()` is a terrible idea, really. If the OP needs *globals* (which is true for the sample), then a `globals().update(vars(parser.parse_args))` would suffice. And then confuse the hell out of everyone that has to ever read or maintain that code. — Martijn Pieters, Sep 21 '13 at 10:56
@MartijnPieters I agree, I just like the `eval` method because, IMO, it is more readable. I'll highlight the part of the answer where I mention it is a bad idea. — mr2ert, Sep 21 '13 at 11:18

How to parse AND store arguments in python?

1 Answers1