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Metadata-Version: 2.1
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Name: autocommand
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Version: 2.2.2
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Summary: A library to create a command-line program from a function
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Home-page: https://github.com/Lucretiel/autocommand
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Author: Nathan West
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License: LGPLv3
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Project-URL: Homepage, https://github.com/Lucretiel/autocommand
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Project-URL: Bug Tracker, https://github.com/Lucretiel/autocommand/issues
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Platform: any
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Classifier: Development Status :: 6 - Mature
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Classifier: Intended Audience :: Developers
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Classifier: License :: OSI Approved :: GNU Lesser General Public License v3 (LGPLv3)
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Classifier: Programming Language :: Python
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Classifier: Programming Language :: Python :: 3
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Classifier: Programming Language :: Python :: 3 :: Only
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Classifier: Topic :: Software Development
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Classifier: Topic :: Software Development :: Libraries
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Classifier: Topic :: Software Development :: Libraries :: Python Modules
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Requires-Python: >=3.7
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Description-Content-Type: text/markdown
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License-File: LICENSE
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[](https://badge.fury.io/py/autocommand)
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# autocommand
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A library to automatically generate and run simple argparse parsers from function signatures.
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## Installation
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Autocommand is installed via pip:
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```
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$ pip install autocommand
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```
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## Usage
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Autocommand turns a function into a command-line program. It converts the function's parameter signature into command-line arguments, and automatically runs the function if the module was called as `__main__`. In effect, it lets your create a smart main function.
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```python
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from autocommand import autocommand
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# This program takes exactly one argument and echos it.
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@autocommand(__name__)
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def echo(thing):
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print(thing)
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```
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```
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$ python echo.py hello
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hello
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$ python echo.py -h
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usage: echo [-h] thing
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positional arguments:
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thing
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optional arguments:
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-h, --help show this help message and exit
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$ python echo.py hello world # too many arguments
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usage: echo.py [-h] thing
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echo.py: error: unrecognized arguments: world
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```
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As you can see, autocommand converts the signature of the function into an argument spec. When you run the file as a program, autocommand collects the command-line arguments and turns them into function arguments. The function is executed with these arguments, and then the program exits with the return value of the function, via `sys.exit`. Autocommand also automatically creates a usage message, which can be invoked with `-h` or `--help`, and automatically prints an error message when provided with invalid arguments.
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### Types
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You can use a type annotation to give an argument a type. Any type (or in fact any callable) that returns an object when given a string argument can be used, though there are a few special cases that are described later.
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```python
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@autocommand(__name__)
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def net_client(host, port: int):
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...
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```
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Autocommand will catch `TypeErrors` raised by the type during argument parsing, so you can supply a callable and do some basic argument validation as well.
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### Trailing Arguments
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You can add a `*args` parameter to your function to give it trailing arguments. The command will collect 0 or more trailing arguments and supply them to `args` as a tuple. If a type annotation is supplied, the type is applied to each argument.
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```python
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# Write the contents of each file, one by one
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@autocommand(__name__)
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def cat(*files):
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for filename in files:
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with open(filename) as file:
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for line in file:
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print(line.rstrip())
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```
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```
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$ python cat.py -h
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usage: ipython [-h] [file [file ...]]
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positional arguments:
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file
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optional arguments:
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-h, --help show this help message and exit
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```
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### Options
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To create `--option` switches, just assign a default. Autocommand will automatically create `--long` and `-s`hort switches.
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```python
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@autocommand(__name__)
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def do_with_config(argument, config='~/foo.conf'):
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pass
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```
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```
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$ python example.py -h
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usage: example.py [-h] [-c CONFIG] argument
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positional arguments:
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argument
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optional arguments:
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-h, --help show this help message and exit
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-c CONFIG, --config CONFIG
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```
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The option's type is automatically deduced from the default, unless one is explicitly given in an annotation:
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```python
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@autocommand(__name__)
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def http_connect(host, port=80):
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print('{}:{}'.format(host, port))
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```
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```
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$ python http.py -h
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usage: http.py [-h] [-p PORT] host
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positional arguments:
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host
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optional arguments:
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-h, --help show this help message and exit
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-p PORT, --port PORT
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$ python http.py localhost
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localhost:80
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$ python http.py localhost -p 8080
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localhost:8080
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$ python http.py localhost -p blah
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usage: http.py [-h] [-p PORT] host
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http.py: error: argument -p/--port: invalid int value: 'blah'
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```
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#### None
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If an option is given a default value of `None`, it reads in a value as normal, but supplies `None` if the option isn't provided.
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#### Switches
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If an argument is given a default value of `True` or `False`, or
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given an explicit `bool` type, it becomes an option switch.
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```python
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@autocommand(__name__)
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def example(verbose=False, quiet=False):
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pass
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```
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```
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$ python example.py -h
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usage: example.py [-h] [-v] [-q]
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optional arguments:
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-h, --help show this help message and exit
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-v, --verbose
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-q, --quiet
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```
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Autocommand attempts to do the "correct thing" in these cases- if the default is `True`, then supplying the switch makes the argument `False`; if the type is `bool` and the default is some other `True` value, then supplying the switch makes the argument `False`, while not supplying the switch makes the argument the default value.
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Autocommand also supports the creation of switch inverters. Pass `add_nos=True` to `autocommand` to enable this.
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```
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@autocommand(__name__, add_nos=True)
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def example(verbose=False):
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pass
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```
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```
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$ python example.py -h
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usage: ipython [-h] [-v] [--no-verbose]
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optional arguments:
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-h, --help show this help message and exit
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-v, --verbose
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--no-verbose
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```
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Using the `--no-` version of a switch will pass the opposite value in as a function argument. If multiple switches are present, the last one takes precedence.
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#### Files
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If the default value is a file object, such as `sys.stdout`, then autocommand just looks for a string, for a file path. It doesn't do any special checking on the string, though (such as checking if the file exists); it's better to let the client decide how to handle errors in this case. Instead, it provides a special context manager called `smart_open`, which behaves exactly like `open` if a filename or other openable type is provided, but also lets you use already open files:
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```python
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from autocommand import autocommand, smart_open
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import sys
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# Write the contents of stdin, or a file, to stdout
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@autocommand(__name__)
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def write_out(infile=sys.stdin):
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with smart_open(infile) as f:
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for line in f:
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print(line.rstrip())
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# If a file was opened, it is closed here. If it was just stdin, it is untouched.
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```
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```
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$ echo "Hello World!" | python write_out.py | tee hello.txt
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Hello World!
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$ python write_out.py --infile hello.txt
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Hello World!
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```
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### Descriptions and docstrings
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The `autocommand` decorator accepts `description` and `epilog` kwargs, corresponding to the `description <https://docs.python.org/3/library/argparse.html#description>`_ and `epilog <https://docs.python.org/3/library/argparse.html#epilog>`_ of the `ArgumentParser`. If no description is given, but the decorated function has a docstring, then it is taken as the `description` for the `ArgumentParser`. You can also provide both the description and epilog in the docstring by splitting it into two sections with 4 or more - characters.
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```python
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@autocommand(__name__)
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def copy(infile=sys.stdin, outfile=sys.stdout):
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'''
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Copy an the contents of a file (or stdin) to another file (or stdout)
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----------
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Some extra documentation in the epilog
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'''
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with smart_open(infile) as istr:
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with smart_open(outfile, 'w') as ostr:
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for line in istr:
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ostr.write(line)
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```
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```
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$ python copy.py -h
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usage: copy.py [-h] [-i INFILE] [-o OUTFILE]
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Copy an the contents of a file (or stdin) to another file (or stdout)
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optional arguments:
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-h, --help show this help message and exit
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-i INFILE, --infile INFILE
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-o OUTFILE, --outfile OUTFILE
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Some extra documentation in the epilog
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$ echo "Hello World" | python copy.py --outfile hello.txt
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$ python copy.py --infile hello.txt --outfile hello2.txt
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$ python copy.py --infile hello2.txt
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Hello World
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```
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### Parameter descriptions
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You can also attach description text to individual parameters in the annotation. To attach both a type and a description, supply them both in any order in a tuple
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```python
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@autocommand(__name__)
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def copy_net(
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infile: 'The name of the file to send',
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host: 'The host to send the file to',
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port: (int, 'The port to connect to')):
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'''
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Copy a file over raw TCP to a remote destination.
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'''
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# Left as an exercise to the reader
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```
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### Decorators and wrappers
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Autocommand automatically follows wrapper chains created by `@functools.wraps`. This means that you can apply other wrapping decorators to your main function, and autocommand will still correctly detect the signature.
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```python
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from functools import wraps
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from autocommand import autocommand
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def print_yielded(func):
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'''
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Convert a generator into a function that prints all yielded elements
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'''
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@wraps(func)
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def wrapper(*args, **kwargs):
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for thing in func(*args, **kwargs):
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print(thing)
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return wrapper
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@autocommand(__name__,
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description= 'Print all the values from START to STOP, inclusive, in steps of STEP',
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epilog= 'STOP and STEP default to 1')
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@print_yielded
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def seq(stop, start=1, step=1):
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for i in range(start, stop + 1, step):
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yield i
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```
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```
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$ seq.py -h
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usage: seq.py [-h] [-s START] [-S STEP] stop
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Print all the values from START to STOP, inclusive, in steps of STEP
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positional arguments:
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stop
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optional arguments:
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-h, --help show this help message and exit
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-s START, --start START
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-S STEP, --step STEP
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STOP and STEP default to 1
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```
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Even though autocommand is being applied to the `wrapper` returned by `print_yielded`, it still retreives the signature of the underlying `seq` function to create the argument parsing.
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### Custom Parser
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While autocommand's automatic parser generator is a powerful convenience, it doesn't cover all of the different features that argparse provides. If you need these features, you can provide your own parser as a kwarg to `autocommand`:
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```python
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from argparse import ArgumentParser
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from autocommand import autocommand
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parser = ArgumentParser()
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# autocommand can't do optional positonal parameters
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parser.add_argument('arg', nargs='?')
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# or mutually exclusive options
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group = parser.add_mutually_exclusive_group()
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group.add_argument('-v', '--verbose', action='store_true')
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group.add_argument('-q', '--quiet', action='store_true')
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@autocommand(__name__, parser=parser)
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def main(arg, verbose, quiet):
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print(arg, verbose, quiet)
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```
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```
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$ python parser.py -h
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usage: write_file.py [-h] [-v | -q] [arg]
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positional arguments:
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arg
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optional arguments:
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-h, --help show this help message and exit
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-v, --verbose
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-q, --quiet
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$ python parser.py
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None False False
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$ python parser.py hello
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hello False False
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$ python parser.py -v
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None True False
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$ python parser.py -q
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None False True
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$ python parser.py -vq
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usage: parser.py [-h] [-v | -q] [arg]
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parser.py: error: argument -q/--quiet: not allowed with argument -v/--verbose
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```
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Any parser should work fine, so long as each of the parser's arguments has a corresponding parameter in the decorated main function. The order of parameters doesn't matter, as long as they are all present. Note that when using a custom parser, autocommand doesn't modify the parser or the retrieved arguments. This means that no description/epilog will be added, and the function's type annotations and defaults (if present) will be ignored.
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## Testing and Library use
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The decorated function is only called and exited from if the first argument to `autocommand` is `'__main__'` or `True`. If it is neither of these values, or no argument is given, then a new main function is created by the decorator. This function has the signature `main(argv=None)`, and is intended to be called with arguments as if via `main(sys.argv[1:])`. The function has the attributes `parser` and `main`, which are the generated `ArgumentParser` and the original main function that was decorated. This is to facilitate testing and library use of your main. Calling the function triggers a `parse_args()` with the supplied arguments, and returns the result of the main function. Note that, while it returns instead of calling `sys.exit`, the `parse_args()` function will raise a `SystemExit` in the event of a parsing error or `-h/--help` argument.
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```python
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@autocommand()
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def test_prog(arg1, arg2: int, quiet=False, verbose=False):
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if not quiet:
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print(arg1, arg2)
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if verbose:
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print("LOUD NOISES")
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return 0
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print(test_prog(['-v', 'hello', '80']))
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```
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```
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$ python test_prog.py
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hello 80
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LOUD NOISES
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0
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```
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If the function is called with no arguments, `sys.argv[1:]` is used. This is to allow the autocommand function to be used as a setuptools entry point.
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## Exceptions and limitations
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- There are a few possible exceptions that `autocommand` can raise. All of them derive from `autocommand.AutocommandError`.
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- If an invalid annotation is given (that is, it isn't a `type`, `str`, `(type, str)`, or `(str, type)`, an `AnnotationError` is raised. The `type` may be any callable, as described in the `Types`_ section.
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- If the function has a `**kwargs` parameter, a `KWargError` is raised.
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- If, somehow, the function has a positional-only parameter, a `PositionalArgError` is raised. This means that the argument doesn't have a name, which is currently not possible with a plain `def` or `lambda`, though many built-in functions have this kind of parameter.
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- There are a few argparse features that are not supported by autocommand.
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- It isn't possible to have an optional positional argument (as opposed to a `--option`). POSIX thinks this is bad form anyway.
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- It isn't possible to have mutually exclusive arguments or options
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- It isn't possible to have subcommands or subparsers, though I'm working on a few solutions involving classes or nested function definitions to allow this.
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## Development
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Autocommand cannot be important from the project root; this is to enforce separation of concerns and prevent accidental importing of `setup.py` or tests. To develop, install the project in editable mode:
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```
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$ python setup.py develop
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```
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This will create a link to the source files in the deployment directory, so that any source changes are reflected when it is imported.
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Reference in New Issue
Block a user