Optparse module makes easy to write command-line tools. It allows argument parsing in the python program.
- optparse make it easy to handle the command-line argument.
- It comes default with python.
- It allows dynamic data input to change the output
Code: Creating an OptionParser object.
Python3
import optparseparser = optparse.OptionParser() |
Defining options:
It should be added one at a time using the add_option(). Each Option instance represents a set of synonymous command-line option string.
Way to create an Option instance are:
OptionParser.add_option(option)
OptionParser.add_option(*opt_str, attr=value, ...)
To define an option with only a short option string:
parser.add_option("-f", attr=value, ....)
And to define an option with only a long option string:
parser.add_option("--foo", attr=value, ....)
Standard Option Actions:
- “store”: store this option’s argument (default).
- “store_const”: store a constant value.
- “store_true”: store True.
- “store_false”: store False.
- “append”: append this option’s argument to a list.
- “append_const”: append a constant value to a list.
Standard Option Attributes:
- Option.action: (default: “store”)
- Option.type: (default: “string”)
- Option.dest: (default: derived from option strings)
- Option.default: The value to use for this option’s destination if the option is not seen on the command line.
Here’s an example of using optparse module in a simple script:
Python3
# import OptionParser class # from optparse module.from optparse import OptionParser# create a OptionParser# class objectparser = OptionParser()# add optionsparser.add_option("-f", "--file", dest = "filename", help = "write report to FILE", metavar = "FILE")parser.add_option("-q", "--quiet", action = "store_false", dest = "verbose", default = True, help = "don't print status messages to stdout")(options, args) = parser.parse_args() |
With these few lines of code, users of your script can now do the “usual thing” on the command-line, for example:
<yourscript> --file=outfile -q
Lets, understand with an example:
Code: Writing python script for print table of n.
Python3
# import optparse moduleimport optparse# define a function for # table of ndef table(n, dest_cheak): for i in range(1,11): tab = i*n if dest_cheak: print(tab) return tab# define a function for # adding optionsdef Main(): # create OptionParser object parser = optparse.OptionParser() # add options parser.add_option('-n', dest = 'num', type = 'int', help = 'specify the n''th table number to output') parser.add_option('-o', dest = 'out', type = 'string', help = 'specify an output file (Optional)') parser.add_option("-a", "--all", action = "store_true", dest = "print", default = False, help = "print all numbers up to N") (options, args) = parser.parse_args() if (options.num == None): print (parser.usage) exit(0) else: number = options.num # function calling result = table(number, options.print) print ("The " + str(number)+ "th table is " + str(result)) if (options.out != None): # open a file in append mode f = open(options.out,"a") # write in the file f.write(str(result) + '\n')# Driver codeif __name__ == '__main__': # function calling Main() |
Output:
python file_name.py -n 4
python file_name.py -n 4 -o
file.txt created
python file_name.py -n 4 -a
For knowing more about this module click here.
