Python函数作为命令行使用

Python函数作为命令行使用

背景

我最近了解了一个快速构建命令行的工具 typer,受到了一些启发。
它可以把一组带有类型注解的 Python 函数,快速地转换成命令行工具。我尝试只用 Python 的内建包,不引入第三方依赖,也实现一个类似的命令行快速构建工具。代码会持续更新,之后会加入更强的功能。

代码实现

TIPS 代码的最新版本在 GitHub Gist 中维护
https://gist.github.com/ChenyangGao/da8b5dc4370425edaef87237cd27fd15

注意:使用下面的代码,请用 Python 3.8 或者以上版本。

文件名称是 func_cmdline.pyPython 实现代码如下:

func_cmdline.py
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#!/usr/bin/env python3
# coding: utf-8

__author__ = "ChenyangGao <https://chenyanggao.github.io/>"
__version__ = (0, 1, 1)
__all__ = ["func_cmdline"]

# Inspired by:
# - https://pypi.org/project/typer/

import inspect

from argparse import ArgumentParser, Namespace, RawDescriptionHelpFormatter
from functools import partial
from textwrap import dedent, indent
from typing import cast, Callable, Optional


def func_cmdline(
fn: Optional[Callable] = None,
/,
parser: Optional[ArgumentParser] = None,
parse_map: dict[type, Callable] = {},
helpinfo_map: dict[str, str] = {},
) -> Callable:
"""装饰器让一个函数,可以作为命令行使用

:param fn: 被装饰的函数
:param parser: 命令行解析器对象
:param parse_map: 不同类型的解析函数的映射,
字符串通过相应的解析函数来转换成对应对象,
如果没有相应的解析函数,则尝试用对象本身
(它的构造器)
:param helpinfo_map: 不同参数的帮助说明,
用于命令行的帮助信息
:param: 返函数`fn`本身,只是它身上绑定了几个属性
.parser 字段,使用的命令行解析器对象
.parse() 方法,解析命令行参数
.run() 方法,解析命令行参数并运行函数`fn`,
返回函数`fn`的执行结果

:return: 被装饰函数本身,添加了几个属性
"""
if fn is None:
return partial(
func_cmdline,
parser=parser,
parse_map=parse_map,
helpinfo_map=helpinfo_map,
)
fn = cast(Callable, fn)
params = inspect.signature(fn).parameters
if parser is None:
parser = ArgumentParser(
formatter_class=RawDescriptionHelpFormatter)
parser = cast(ArgumentParser, parser)
if parser.epilog is None:
parser.epilog = ""
if fn.__doc__ is not None:
parser.epilog += "documentation:\n" + \
indent(fn.__doc__, " ")
parser.epilog += "\n\nsource code:\n" + \
indent(dedent(inspect.getsource(fn)), " ")
abbrs: dict[str, int] = {}
for name, param in params.items():
kargs: dict = {"dest": name, "help": helpinfo_map.get(name)}
kind = param.kind
if kind is inspect._ParameterKind.VAR_POSITIONAL:
kargs["required"] = False
kargs["nargs"] = "*"
kargs["default"] = []
elif kind is inspect._ParameterKind.VAR_KEYWORD:
continue
default = param.default
if default is inspect._empty:
kargs.setdefault("required", True)
else:
kargs["default"] = default
anno = param.annotation
if anno is not inspect._empty:
if anno is bool:
kargs["required"] = False
if "default" in kargs:
if kargs["default"]:
kargs["action"] = "store_false"
else:
kargs["action"] = "store_true"
else:
kargs["action"] = "store_true"
elif anno is list:
kargs["nargs"] = "*"
elif getattr(anno, "__origin__", None) is list and len(anno.__args__) == 1:
kargs["nargs"] = "*"
kargs["type"] = parse_map.get(anno.__args__[0], anno.__args__[0])
else:
kargs["type"] = parse_map.get(anno, anno)
names = []
first_letter = name[0]
n = abbrs.setdefault(first_letter, 0)
if n == 0:
abbr = first_letter
else:
abbr = f"{first_letter}{n}"
abbrs[first_letter] += 1
names.append(f"-{abbr}")
names.append(f"--{name}")
if "_" in name:
names.append(f"--{name.replace('_', '-')}")
parser.add_argument(*names, **kargs)
def parse(argv: Optional[list[str]] = None) -> Namespace:
nonlocal parser
parser = cast(ArgumentParser, parser)
return parser.parse_args(argv)
def run(argv: Optional[list[str]] = None):
"解析命令行参数,默认使用"
nonlocal fn, parser
fn = cast(Callable, fn)
parser = cast(ArgumentParser, parser)
args = parser.parse_args(argv).__dict__
pargs = []
kargs = {}
for name, param in params.items():
kind = param.kind
if name in args:
if kind.value < 2:
pargs.append(args[name])
elif kind.value == 2:
pargs.extend(args[name])
else:
kargs[name] = args[name]
return fn(*pargs, **kargs)
setattr(fn, "parser", parser)
setattr(fn, "parse", parse)
setattr(fn, "run", run)
return fn


if __name__ == "__main__":
from datetime import datetime

@func_cmdline(
parse_map={
datetime: lambda s: datetime.strptime(s, "%Y-%m-%d %H:%M:%S"),
},
helpinfo_map=dict(
a="参数a", b="参数b", c="参数c",
d="参数d", e="参数e",
)
)
def foo(
a: int, /, b: bool = False, *c: float,
d: list[datetime], e: complex = 4,
):
"Example for function as command line."
print(locals())

foo.run()

使用说明

模块 func_cmdline.py 自带了一个实例:

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from datetime import datetime

@func_cmdline(
parse_map={
datetime: lambda s: datetime.strptime(s, "%Y-%m-%d %H:%M:%S"),
},
helpinfo_map=dict(
a="参数a", b="参数b", c="参数c",
d="参数d", e="参数e",
)
)
def foo(
a: int, /, b: bool = True, *c: float,
d: list[datetime], e: complex = 1j,
):
"Example for function as command line."
print(locals())

foo.run()

直接运行模块,输出如下:

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$ python func_cmdline.py -h
usage: func_cmdline.py [-h] -a A [-b] [-c [C ...]] -d [D ...] [-e E]

optional arguments:
-h, --help show this help message and exit
-a A, --a A 参数a
-b, --b 参数b
-c [C ...], --c [C ...]
参数c
-d [D ...], --d [D ...]
参数d
-e E, --e E 参数e

documentation:
Example for function as command line.

source code:
@func_cmdline(
parse_map={
datetime: lambda s: datetime.strptime(s, "%Y-%m-%d %H:%M:%S"),
},
helpinfo_map=dict(
a="参数a", b="参数b", c="参数c",
d="参数d", e="参数e",
)
)
def foo(
a: int, /, b: bool = False, *c: float,
d: list[datetime], e: complex = 1j,
):
"Example for function as command line."
print(locals())

随便传入一些必需的参数,不传可选参数:

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$ python func_cmdline.py --a 1 --d '2021-01-01 00:00:00' '2021-02-01 00:00:00' '2021-03-01 00:00:00'
{'a': 1, 'b': False, 'd': [datetime.datetime(2021, 1, 1, 0, 0), datetime.datetime(2021, 2, 1, 0, 0), datetime.datetime(2021, 3, 1, 0, 0)], 'e': 1j, 'c': ()}

对各个参数随便传入一些可用的值:

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$ python func_cmdline.py --a 1 -b -c 2 3 4 --d '2021-01-01 00:00:00' '2021-02-01 00:00:00' '2021-03-01 00:00:00' -e '5+6j'
{'a': 1, 'b': True, 'd': [datetime.datetime(2021, 1, 1, 0, 0), datetime.datetime(2021, 2, 1, 0, 0), datetime.datetime(2021, 3, 1, 0, 0)], 'e': (5+6j), 'c': (2.0, 3.0, 4.0)}

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