Python笔记：argparse 命令行模块的使用_python argparse expected one argument-优快云博客

argparse 是什么

argparse是Python标准库中推荐的命令行解析模块，可以轻松地为命令行参数编写用户友好型命令行界面。

测试环境

Mac
python3

导入模块

#!/usr/bin/env python
# encoding: utf-8

import argparse

必选参数

parser = argparse.ArgumentParser()
parser.add_argument("echo")
args = parser.parse_args()
print(args.echo)

测试：

$ python test.py wowo
wowo

可选参数

parser = argparse.ArgumentParser()
parser.add_argument("-v", "--verbosity", help="increase output verbosity")
args = parser.parse_args()
if args.verbosity:
        print(args) # Namespace(verbosity='2')
        print(args.verbosity) # 2
        print("verbosity turned on") # verbosity turned on

测试：

$ python test.py --verbosity 2
Namespace(verbosity=‘2’)
2
verbosity turned on

默认无参数错误示例

parser = argparse.ArgumentParser()
parser.add_argument("-v", "--verbosity", help="increase output verbosity")
args = parser.parse_args()
if args.verbosity:
        print("verbosity turned on")

测试：

$ python test.py -v
usage: test.py [-h] [-v VERBOSITY]
test.py: error: argument -v/–verbosity: expected one argument

支持无参数的写法

parser = argparse.ArgumentParser()
parser.add_argument("-v", "--verbosity", help="increase output verbosity", action="store_true")
args = parser.parse_args()
if args.verbosity:
        print("verbosity turned on")

测试：

$ python test.py -v
verbosity turned on

type 类型

parser = argparse.ArgumentParser()
parser.add_argument('x', type=int, help="the base")
args = parser.parse_args()
answer = args.x ** 2 # 此处是开方运算
print(answer)

测试：

正确示例：
$ python test.py 3
9
$ python test.py ‘31’
961

错误示例：
$ python test.py ‘31a’
usage: test.py [-h] x
test.py: error: argument x: invalid int value: ‘31a’

支持参数限定范围

parser = argparse.ArgumentParser()
parser.add_argument("square", type=int,
                    help="display a square of a given number")
parser.add_argument("-v", "--verbosity", type=int, choices=[0, 1, 2],
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square ** 2
if args.verbosity == 2:
    print("the square of {} equals {}".format(args.square, answer))
elif args.verbosity == 1:
    print("{}^2 == {}".format(args.square, answer))
else:
    print(answer)

测试：

$ python test.py 1 -v 2
the square of 1 equals 1

$ python test.py 1 -v 1
1^2 == 1

$ python test.py 1 -v 0
1

$ python test.py 1 -v 3
usage: test.py [-h] [-v {0,1,2}] square
test.py: error: argument -v/–verbosity: invalid choice: 3 (choose from 0, 1, 2)

$ python test.py 1
1

全局注释和互斥参数

parser = argparse.ArgumentParser(description="calculate X to the power of Y")
group = parser.add_mutually_exclusive_group()
group.add_argument("-v", "--verbose", action="store_true")
group.add_argument("-q", "--quiet", action="store_true")
parser.add_argument("x", type=int, help="the base")
parser.add_argument("y", type=int, help="the exponent")
args = parser.parse_args()
answer = args.x ** args.y

if args.quiet:
    print(answer)
elif args.verbose:
    print("{} to the power {} equals {}".format(args.x, args.y, answer))
else:
    print("{}^{} == {}".format(args.x, args.y, answer))

测试：

$ python test.py -h
usage: test.py [-h] [-v | -q] x y

calculate X to the power of Y

positional arguments:
x the base
y the exponent

optional arguments:
-h, --help show this help message and exit
-v, --verbose
-q, --quiet

$ python test.py -v 2 3
2 to the power 3 equals 8

$ python test.py -q 2 3
8

$ python test.py 2 3
2^3 == 8

说明：-q 和 -v 是互斥的参数，可以看出，-q和-v不出现，或仅出现一个都可以，同时出现就会报错。

给参数设定默认值

parser = argparse.ArgumentParser(description="calculate X to the power of Y")
parser.add_argument("square", type=int,
                    help="display a square of a given number")
parser.add_argument("-v", "--verbosity", type=int, choices=[0, 1, 2], default=1,
                    help="increase output verbosity")
args = parser.parse_args()
answer = args.square**2
if args.verbosity == 2:
    print("the square of {} equals {}".format(args.square, answer))
elif args.verbosity == 1:
    print("{}^2 == {}".format(args.square, answer))
else:
    print(answer)