用原生的参数解析工具非常繁琐，而click工具入手就非常简单了，而且直观。建立以下这个程序a.py[1], cli会有子命令make，make有选项--work：
1 import click
2
3 @click.group()
4 def cli():
5 print("cli")
6
7 @cli.command()
8 @click.option('--work', default=None)
9 def make(work):
10 print(type(work))
11 print(work)
12
13 if __name__ == '__main__':
14 cli()
a.py在bash下执行：
$ python a.py
Usage: a.py [OPTIONS] COMMAND [ARGS]...
Options:
--help Show this message and exit.
Commands:
make
在bash下执行:
$ python a.py make
cli
None
a.py在bash下执行：
$ python a.py make --work='我'
cli
我
a.py修改, 增加make的参数name:
7 @cli.command()
8 @click.option('--work', default=None)
9 @click.argument('name')
10 def make(work, name):
11 print(u'work: {}, type: {}'.format(work, type(work)))
12 print(u'name: {}'.format(name))
在bash下执行：
$ python a.py make --work='我'
cli
Usage: a.py make [OPTIONS] NAME
Try "a.py make --help" for help.
Error: Missing argument "NAME".
注意执行时提示：Error: Missing argument "NAME"。 表示需要参数NAME。我们重新执行：
$ python a.py make --work='我' '张三'
cli
work: 我, type:
name: 张三
可以用click.Choice限定参数或者选项的取值范围，修改代码：
7 @cli.command()
8 @click.option('--work', default=None, type=click.Choice(['全职', '兼职']))
9 @click.argument('name')
10 def make(work, name):
11 print(u'work: {}, type: {}'.format(work, type(work)))
12 print(u'name: {}'.format(name))
我们重新执行：
$ python a.py make --work='全' '张三'
cli
/home/jzhou/env/wf/lib/python2.7/site-packages/click/types.py:156: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
if value in self.choices:
/home/jzhou/env/wf/lib/python2.7/site-packages/click/types.py:176: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
if normed_value in normed_choices:
Traceback (most recent call last):
File "a.py", line 16, in
cli()
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/core.py", line 764, in __call__
return self.main(*args, **kwargs)
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/core.py", line 717, in main
rv = self.invoke(ctx)
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/core.py", line 1135, in invoke
sub_ctx = cmd.make_context(cmd_name, args, parent=ctx)
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/core.py", line 641, in make_context
self.parse_args(ctx, args)
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/core.py", line 940, in parse_args
value, args = param.handle_parse_result(ctx, opts, args)
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/core.py", line 1469, in handle_parse_result
value = self.full_process_value(ctx, value)
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/core.py", line 1790, in full_process_value
return Parameter.full_process_value(self, ctx, value)
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/core.py", line 1438, in full_process_value
value = self.process_value(ctx, value)
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/core.py", line 1428, in process_value
return self.type_cast_value(ctx, value)
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/core.py", line 1417, in type_cast_value
return _convert(value, (self.nargs != 1) + bool(self.multiple))
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/core.py", line 1415, in _convert
return self.type(value, self, ctx)
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/types.py", line 39, in __call__
return self.convert(value, param, ctx)
File "/home/jzhou/env/wf/lib/python2.7/site-packages/click/types.py", line 180, in convert
(value, ', '.join(self.choices)), param, ctx)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe5 in position 16: ordinal not in range(128)
这个是因为click在python 2环境下没有考虑把参数或者选项转化为unicode，下载click_patch[2], clone后在目录下安装：
$ git clone https://github.com/fininfotech/click_patch.git
Cloning into 'click_patch'...
remote: Enumerating objects: 11, done.
remote: Counting objects: 100% (11/11), done.
remote: Compressing objects: 100% (8/8), done.
remote: Total 11 (delta 1), reused 8 (delta 1), pack-reused 0
Unpacking objects: 100% (11/11), done.
$ cd click_patch
$ python setup.py install
running install
....
修改a.py:
1 # -*- coding:utf-8 -*-
2 import click
3 import click_patch
4
5 @click.group()
6 def cli():
7 print("cli")
8
9 @cli.command()
10 @click.option('--work', default=None, type=click.Choice([u'全职', u'兼职']))
11 @click.argument('name')
12 def make(work, name):
13 print(u'work: {}, type: {}'.format(work, type(work)))
14 print(u'name: {}'.format(name))
15
16 if __name__ == '__main__':
17 cli()
继续执行：
$ python a.py make --work='全' '张三'
cli
Usage: a.py make [OPTIONS] NAME
Try "a.py make --help" for help.
Error: Invalid value for "--work": invalid choice: 全. (choose from 全职, 兼职)
$ python a.py make --work='全职' '张三'
cli
work: 全职, type:
name: 张三
总的来说，click用来做命令行工具非常方便，但是在python 2.7环境下还存在一些字符编码上的问题，可以使用click_patch来改正。
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本文所有代码在fedora 27环境下测试，python 2.7.15。 ↩
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click_patch目前只是参考实现，不建议在生产上使用，如果要在生产上用，请务必自己确认和测试代码。 ↩