Summary of methods for obtaining command line parameters in Python

Introducing python's method of obtaining command line parameters: getopt module and argparse module.

Python version: 2.7

1. getopt module

Mainly uses the functions in the module:

options, args = getopt.getopt(args, shortopts, longopts=[])

Parameter args: usually sys.argv[1:]. Filter out sys.argv[0], which is the name of the executed script and is not counted as a command line parameter.

Parameter shortopts: short format analysis string. For example: "hp:i:", there is no colon after h, which means there are no parameters; there are colons after p and i, which means there are parameters.

Parameter longopts: long format analysis string list. For example: ["help", "ip=", "port="], there is no equal sign after help, which means there are no parameters; there is a colon after ip and port, which means there are parameters.

The return value options is a list with tuples as elements. The form of each tuple is: (option string, additional parameters), such as: ('-i', '192.168.0.1')

The return value args is a list, the elements of which are parameters that do not contain '-' or '--'.

Run the following command on the command line:

python test_getopt.py -i 192.168.0.1 -p 80 123 a

or

python test_getopt.py -ip=192.168.0.1 --port=80 123 a

test_getopt.py code is as follows:

#encoding=utf-8

import getopt
import sys

def main(argv):
    try:
        options, args = getopt.getopt(argv, "hp:i:", ["help", "ip=", "port="])
    except getopt.GetoptError:
        sys.exit()

    for option, value in options:
        if option in ("-h", "--help"):
            print("help")
        if option in ("-i", "--ip"):
            print("ip is: {0}".format(value))
        if option in ("-p", "--port"):
            print("port is: {0}".format(value))

    print("error args: {0}".format(args))

if __name__ == '__main__':
    main(sys.argv[1:])

The running results are as follows:

2. argparse module

A standard module used to parse command line options and parameters.

Usage steps:

1: import argparse　#Import module

2: parser = argparse.ArgumentParser()　#Create parsing object

3: parser .add_argument()　#Add the command line options and parameters used to the object

4: parser.parser_args()　#Parse the command line

Next details Introducing the methods ArgumentParser and add_argument:

ArgumentParser(prog=None, usage=None, description=None, epilog=None, parents=[], formatter_class=argparser.HelpFormatter, prefix_chars='-', fromfile_prefix_chars= None, argument_default=None, conflict_handler='error', add_help=True)

The parameters have default values. When running the program due to incorrect parameters or when calling the parser.print_help() method, it will Print these descriptions. Generally, only the parameter description needs to be passed.

add_argument(name or flags... [, action] [, nargs] [, const] [, default] [, type] [, choices] [, required] [, help] [, metavar] [, dest])

The common parameters are explained as follows:

name or flags: command line parameter name or option, such as -p, --port

action:

Store: The default action mode, stores the value to the specified variable

Store_const: The storage value is specified in the const part of the parameter, often used to implement non-Boolean command line flags

store_true/store_false: Boolean switch. The default value of store_true is False. If the Boolean switch is entered on the command line, the value is True. The opposite of store_false

Append: Store the value into the list, this parameter can be reused

Append_const: Store the value into the list, the stored value is specified in the const part of the parameter

count: Statistics The number of input parameter abbreviations

Version: Output version information, and then exit the script

nargs: The number of command line parameters, generally represented by wildcards: ? means only one is used, * means 0 to more, + means 1 to more

default: Default value

type: The type of parameter, the default is string type, it can also be float, Types such as int and Boolean

choices: the range of input values ​​

required: the default is False, if True, it means that the parameter must be entered

help: the help prompt used Information

dest: The corresponding variable name of the parameter in the program, such as: add_argument("-a", dest="code_name"), use parser.code_name in the script to access the value of the command line option

The sample script test_argparse.py code is as follows:

 1 #encoding=utf-8 2 import argparse 3  4 def main(args): 5     print("--address {0}".format(args.code_address))    #args.address会报错，因为指定了dest的值 6     print("--flag {0}".format(args.flag))   #如果命令行中该参数输入的值不在choices列表中，则报错 7     print("--port {0}".format(args.port))   #prot的类型为int类型，如果命令行中没有输入该选项则报错 8     print("-l {0}".format(args.log))  #如果命令行中输入该参数，则该值为True。因为为短格式"-l"指定了别名"--log"，所以程序中用args.log来访问 9 10 if __name__ == '__main__':11     parser = argparse.ArgumentParser(usage="it's usage tip.", description="help info.")12     parser.add_argument("--address", default=80, help="the port number.", dest="code_address")13     parser.add_argument("--flag", choices=['.txt', '.jpg', '.xml', '.png'], default=".txt", help="the file type")14     parser.add_argument("--port", type=int, required=True, help="the port number.")15     parser.add_argument("-l", "--log", default=False, action="store_true", help="active log info.")16 17     args = parser.parse_args()18     main(args)

Run the following commands respectively:

python test_argparse.py

##python test_argparse.py --port 80

##python test_argparse.py --port 80 --flag apk

python test_argparse.py --port 80 -l

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