The most complete summary | talk about several ways of Python command line parameterization!

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1. Preface

Hello everyone , I'm Ango ！

In daily writing Python In the process of scripting , We often need to pass in some variable parameters in combination with command line parameters , Make the project more flexible and convenient

In this article, I will list the build Python Of command line arguments 4 There are two common ways

They are ：

• built-in  sys.argv modular

• built-in  argparse modular

• built-in  getopt modular

• Third party dependency Library  click

2. sys.argv

Easiest to build command line parameters 、 A common way is to use the built-in 「 sys.argv 」 modular

It passes parameters in an ordered list , Therefore, the order of parameter transfer must be fixed

therefore , This method is applicable to projects with few parameters and fixed scenarios

import sys
if __name__ == '__main__':
    #  Get parameter list
    #  Be careful ：sys.argv[0]  Represents the first parameter , namely ： Script name 「1_sys.argv.py」
    #  List of other parameters
    args = sys.argv[1:]
    #  Number of parameters
    args_length = len(sys.argv) if sys.argv else 0
    print(" Exclude run master file parameters , Other parameter lists are :", args)
    print(" Total number of parameters ：", args_length)
#  Use
# python3 1_sys.argv.py arg1 arg2
#  Exclude run master file parameters , Other parameter lists are : [arg1, arg1]
#  Total number of parameters ：3

It should be noted that , Pass... In the script 「 sys.argv 」 Get the parameter list , The first parameter represents the name of the script main file

3. argparse

Built in argparse The module can easily write friendly command line parameter scripts , And it can automatically generate help manuals , Clear error messages can be thrown when the user passes invalid parameters into the program

Official documents ：

https://docs.python.org/zh-cn/3.10/library/argparse.html

Use it to build command line arguments that contain 3 A step ：

• Build a parameter resolution object and add parameters

• Add parameter

• Analytical parameters
  

3-1 Build command line parameter parsing object 

import argparse
...
#  Build a command line parameter parsing object
parser = argparse.ArgumentParser(description=' Command line arguments ')
...

3-2 Add command line arguments 

 It's important to point out that ,--arg1 Used to specify the parameter name ,-a1 representative dest Target variable value （ Abbreviation ）

...
#  Set up 3 Parameters
#  Parameters 1：arg1, integer , It is not necessary to pass in parameters
#  Parameters 2：arg2, character string , It is not necessary to pass in parameters , Include default values 「xag」
#  Parameters 3：arg3, String type , Parameters that must be passed in
parser.add_argument('--arg1', '-a1', type=int, help=' Parameters 1, Not a required parameter ')
parser.add_argument('--arg2', '-a2', type=str, help=' Parameters 2, Not a required parameter , Include default values ', default='xag')
parser.add_argument('--arg3', '-a3', type=str, help=' Parameters 3, Necessary parameters ', required=True)
...

3-3 Analyze the parameter value 

...
#  Analytical parameters , Get all command line parameters （Namespace）, Then turn it into a dictionary
args = vars(parser.parse_args())
#  Get all parameters
print(" All command line parameters are :")
for key in args:
    print(f" Command line parameter name :{key}, Parameter values :{args[key]}")
...

 When you use it , We can go through 「 -h / --help 」 Command parameters view help documentation 

#  View the command line parameter help documentation
python3 2_argparse.py --help
#  or
python3 2_argparse.py -h

Added above 3 Parameters , Parameters arg1、arg2 Non mandatory value transfer ,arg3 Must pass value , Another parameter arg2 Default value specified

#  Parameters arg3 must , Parameters arg1 And parameters arg2 Not necessary , The parameter arg2 Set the default value
#  Pass in the parameter arg3
# python3 2_argparse.py --arg3 123
# python3 2_argparse.py -a3 123 
[email protected] args % python3 2_argparse.py -a3 123  
All command line parameters are :
Command line parameter name :arg1, Parameter values :None
Command line parameter name :arg2, Parameter values :xag
Command line parameter name :arg3, Parameter values :123
#  Pass in the parameter arg1、arg3
[email protected] args % python3 2_argparse.py -a1 111  -a3 123  
All command line parameters are :
Command line parameter name :arg1, Parameter values :111
Command line parameter name :arg2, Parameter values :xag
Command line parameter name :arg3, Parameter values :123
#  Pass in the parameter arg1、arg2、arg3
[email protected] args % python3 2_argparse.py -a1 111 -a2 222  -a3 123
All command line parameters are :
Command line parameter name :arg1, Parameter values :111
Command line parameter name :arg2, Parameter values :222
Command line parameter name :arg3, Parameter values :123

4. getopt

getopt yes Python A built-in standard module in , Can combine sys.argv modular , Directly parse script runtime parameters

Use format ：getopt(args,shortopts,longopts = [])

among

• args

  parameter list , Can pass sys.argv obtain , You can refer to the above

• shortopts A string consisting of short parameters

  Define short parameters , If the parameter has a value , You need to append a... After the short parameter 「 : 」 Symbol

  How to use parameters ：-n 23

• longopts Long parameter list

  When defining a long parameter list , If a parameter has a value , You need to append a... After the short parameter 「 = 」 Symbol

  How to use parameters ：--port 8080

Take the incoming database connection parameters as an example （ Parameters include ip、 user name 、 password 、 Database name ） Explain

from getopt import getopt
import sys
#  To obtain parameters
# sys.argv[1:]： Get all the command line parameters except the script file name
# opts： A tuple list of all options and their input values
# args： Remove the rest of the useful input
opts, args = getopt(sys.argv[1:], 'i:u:p:d:', ['ip=', 'user=', 'pwd=', 'db='])
#  Get parameter value
#  Short parameters
# python3 4_getopt.py -i 127.0.0.1 -u root -p 123456 -d mysqldb
#  Long parameters
# python3 4_getopt.py --ip 127.0.0.1 -u root -p 123456 -d mysqldb
ip_pre = [item[1] for item in opts if item[0] in ('-i', '--ip')]
ip = ip_pre[0] if len(ip_pre) > 0 else None
print(" Parameters ip：", ip)
user_pre = [item[1] for item in opts if item[0] in ('-u', '--user')]
user = user_pre[0] if len(user_pre) > 0 else None
print(" Parameters user：", user)
pwd_pre = [item[1] for item in opts if item[0] in ('-p', '--pwd')]
pwd = pwd_pre[0] if len(pwd_pre) > 0 else None
print(" Parameters pwd：", pwd)
db_pre = [item[1] for item in opts if item[0] in ('-d', '--db')]
db = db_pre[0] if len(db_pre) > 0 else None
print(" Parameters db：", db)

When running the script , We can use 「  Short parameters  」 or 「  Long parameters  」 Transfer in form

#  test
#  Short parameters
python3 4_getopt.py -i 127.0.0.1 -u root -p 123456 -d mysqldb
#  Long parameters
python3 4_getopt.py --ip 127.0.0.1 --user root --pwd 123456 --db mysqldb

5. click

click As a third-party dependent Library , It encapsulates a number of methods for command-line tools , It is very convenient to implement command line parameters

Project address ：https://pypi.org/project/click/

First , We need to install dependency Libraries  click

import click
#  Installation dependency
# pip3 install -U click
@click.command()
@click.option('--arg1', default='111', help=' Parameters arg1, The default value is 「111」')
@click.option('--arg2', type=int, help=' Parameters arg2')
@click.option('--arg3', type=str, help=' Parameters arg3')
def start(arg1, arg2, arg3):
    """
     Based on parameters arg1、 Parameters arg2、 Parameters arg3 Run the project
    :param arg1:
    :param arg2:
    :param arg3:
    :return:
    """
    print(" Parameters arg1 The value is :", arg1)
    print(" Parameters arg2 The value is :", arg2)
    print(" Parameters arg3 The value is :", arg3)
if __name__ == '__main__':
    start()

then , You can configure parameters on the main running function through the decorator

such as , The above defines 3 Two command line arguments arg1、arg2、arg3, And set the parameter type and default value

Last , When running the script, you only need to pass the corresponding value according to the parameter settings

#  No parameters
[email protected] args % python3 3_click.py 
Parameters arg1 The value is : 111
Parameters arg2 The value is : None
Parameters arg3 The value is : None
#  Include parameters arg1
[email protected] args % python3 3_click.py --arg1 test1
Parameters arg1 The value is : test1
Parameters arg2 The value is : None
Parameters arg3 The value is : None
#  Include parameters arg1、arg2
#  Be careful ：arg2 The parameter type of is integer , The passed in parameter must be able to be converted to an integer , Otherwise, an error will be reported
[email protected] args % python3 3_click.py --arg1 test1 --arg2 222  
Parameters arg1 The value is : test1
Parameters arg2 The value is : 222
Parameters arg3 The value is : None
#  Include parameters arg1、arg2、arg3
[email protected] args % python3 3_click.py --arg1 test1 --arg2 222 --arg3 test3
Parameters arg1 The value is : test1
Parameters arg2 The value is : 222
Parameters arg3 The value is : test3

6. Last

The above explains the implementation through an example Python Command line arguments are common 4 Ways of planting

For some simple and informal scenarios , Personally, I think we can consider using sys.argv Modules quickly build command line parameters ; For some parameters, there are many 、 Formal production environment for users , It is suggested to make use of argparse Module or click Dependency to create command line parameters

I have uploaded the source code to the background , Reply key 「 args 」 Get all the source code

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