Python命令行参数argv和argparse该如何使用

# test_argv.py

import sys

args = sys.argv
print(f'args = {args}')

>>> output
➜ git:(master) python3 test_argv.py     
args = ['test_argv.py']
➜ git:(master) ✗ python3 test_argv.py 1 2 3
args = ['test_argv.py', '1', '2', '3']
➜ git:(master) ✗ python3 test_argv.py 1 2 3 'hello world !'
args = ['test_argv.py', '1', '2', '3', 'hello world !']

import argparse

# 初始化一个parser对象
parser = argparse.ArgumentParser(description='test module of argparse')

# 指定-n/--number的参数
# 类型为int
# help为简短地说明
parser.add_argument(
  '-n', '--number', type=int,
  help='args of number'
)

# 指定-o/--output参数
# 并限制类型为：['txt', 'csv', 'doc']
parser.add_argument(
  '-o', '--output', type=str,
  choices=['txt', 'csv', 'doc'],
  help='output method'
)

# 指定-d/--default参数
# 并限制类型为：['txt', 'csv', 'doc']
parser.add_argument(
  '-d', '--default', type=int,
  choices=[_ for _ in range(1, 10)],
  default=5,
  help='default'
)

# 指定位置参数foo
parser.add_argument('foo')

args = parser.parse_args()
print(f'args = {args}')

# 获取指定参数
print(
  f'number = {args.number}, type = {type(args.number)}\n'
  f'output = {args.output}, type = {type(args.output)}\n'
  f'default = {args.default}, type = {type(args.default)}\n'
  f'foo = {args.foo}, type = {type(args.foo)}'
)

# -h - 打印help
➜ git:(master) ✗ python3 test_argv.py -h
usage: test_argv.py [-h] [-n NUMBER] [-o {txt,csv,doc}]
          [-d {1,2,3,4,5,6,7,8,9}]
          foo

test module of argparse

positional arguments:
 foo

optional arguments:
 -h, --help      show this help message and exit
 -n NUMBER, --number NUMBER
            args of number
 -o {txt,csv,doc}, --output {txt,csv,doc}
            output method
 -d {1,2,3,4,5,6,7,8,9}, --default {1,2,3,4,5,6,7,8,9}
            default
# 不带参数运行，结果为None
➜ git:(master) ✗ python3 test_argv.py  
args = Namespace(number=None, output=None)
number = None
output = None

# 带参数运行
➜ git:(master) ✗ python3 test_argv.py -n 33 --output txt
args = Namespace(number=33, output='txt')
number = 33, type = class 'int'>
output = txt, type = class 'str'>

# 参数格式错误
➜ git:(master) ✗ python3 test_argv.py -n str     
usage: test_argv.py [-h] [-n NUMBER] [-o {txt,csv,doc}]
test_argv.py: error: argument -n/--number: invalid int value: 'str'
➜ git:(master) ✗ python3 test_argv.py -o excel    
usage: test_argv.py [-h] [-n NUMBER] [-o {txt,csv,doc}]
test_argv.py: error: argument -o/--output: invalid choice: 'excel' (choose from 'txt', 'csv', 'doc')

# 默认参数 
➜ git:(master) ✗ python3 test_argv.py   
args = Namespace(default=5, number=None, output=None)
number = None, type = class 'NoneType'>
output = None, type = class 'NoneType'>
output = 5, type = class 'int'>