How Python obtains command-line arguments

This article describes the SYS in Python and the getopt module handles command-line arguments

If you want to pass parameters to the Python script, what is the corresponding argc in Python, argv (command-line arguments for the C language)?
Module Required: SYS
Number of parameters: Len (SYS.ARGV)
Script Name: sys.argv[0]
Parameter 1:sys.argv[1]
Parameter 2:sys.argv[2]

test.py

1 Import sys

2 print "Script name:", Sys.argv[0]

3 for I in range (1, Len (SYS.ARGV)):

4 print "Parameters", I, Sys.argv[i]
>>>python test.py Hello World
Script Name: test.py
Parameter 1 Hello
Parameter 2 World

Use command-line options in Python:
For example we need a convert.py script. It works by processing one file and outputting the processed results to another file.
The script is required to meet the following criteria:
1. Use the-I-O option to distinguish whether the parameter is an input file or an output file.
>>> python convert.py-i inputfile-o outputfile
2. If you do not know what parameters convert.py need, print out the help information with-H
>>> python convert.py-h

getopt function Prototype:
Getopt.getopt (args, options[, long_options])

convert.py

Import SYS, getopt

02

opts, args = Getopt.getopt (sys.argv[1:], "Hi:o:")

Input_file= ""

Output_file= ""

06

On OP, value in opts:

If op = = "-I":

Input_file = value

Ten elif op = = "-O":

Output_file = value

Elif op = = "-H":

Usage ()

Sys.exit ()

Code Explanation:
A) Sys.argv[1:] for the parameter list to be processed, sys.argv[0] is the script name, so use sys.argv[1:] To filter out the script name.
b) "Hi:o:" When an option simply represents a switch state, that is, the option character is written in the parse string when no additional parameters are followed. When an optional item is followed by an additional parameter, the Write option character in the parse string is appended with a ":" Number. So "Hi:o:" means "h" is a switch option; "I:" and "O:" means that a parameter should be followed.
c) Call the Getopt function. The function returns two lists: OPTs and args. OPTs the format information for the analysis. Args is the remaining command-line argument that is not part of the format information. OPTs is a two-tuple list. Each element is: (option string, additional parameter). Empty string If no additional parameters are available.

The third parameter of the GETOPT function [, Long_options] is an optional long option parameter, and the example above is a short option (such as-i-o)
Examples of long option formats:
--version
--file=error.txt
Allow a script to support both short and long options
Getopt.getopt (sys.argv[1:], "Hi:o:", ["Version", "file="])

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How Python obtains command-line arguments