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124 lines
4.3 KiB
Markdown
124 lines
4.3 KiB
Markdown
# Using utils.IRCParser()
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**As of 22/02/2017 (1.2-dev), PyLink allows plugin creators to either parse command arguments themselves
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or use a sub-classed instance of [argparse.ArgumentParser()](https://docs.python.org/3/library/argparse.html)
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to parse their arguments.**
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First off, you will already have access to IRCParser due to importing `utils`.
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Otherwise, this is how to include it...
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```python
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from pylinkirc import utils
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```
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When you add a command that you want to use `utils.IRCParser()` with, the following is a guide on how to add arguments.
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**Note**: Most if not all the examples are from Python's argparse documentation, linked above.
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#### Positional (Named) Arguments
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```python
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SomeParser.add_argument('argname')
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```
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#### Flag Arguments / Switch Arguments
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```python
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SomeParser = utils.IRCParser()
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SomeParser.addargument('-a', '--argumentname')
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```
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##### Action
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Actions define what to do when given an argument (i.e. whether it is used by itself or as some other sort of value).
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Here are some of the actions that `argparse` defines:
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* `store` - just stores the value given. This is the default when an action isn't provided.
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```python
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>>> parser = argparse.ArgumentParser()
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>>> parser.add_argument('--foo')
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>>> parser.parse_args('--foo 1'.split())
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Namespace(foo='1')
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```
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* `store_true`/`store_false` - used when you just want to check if an argument was used.
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```python
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>>> parser = argparse.ArgumentParser()
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>>> parser.add_argument('--foo', action='store_true')
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>>> parser.add_argument('--bar', action='store_false')
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>>> parser.add_argument('--baz', action='store_false')
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>>> parser.parse_args('--foo --bar'.split())
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Namespace(foo=True, bar=False, baz=True)
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```
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* `append` - additively stores arguments if a switch is given multiple times.
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```python
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>>> parser = argparse.ArgumentParser()
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>>> parser.add_argument('--foo', action='append')
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>>> parser.parse_args('--foo 1 --foo 2'.split())
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Namespace(foo=['1', '2'])
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```
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* `count` - counts how many times an argument was used (for flag/switch arguments only)
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```python
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>>> parser = argparse.ArgumentParser()
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>>> parser.add_argument('--verbose', '-v', action='count')
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>>> parser.parse_args(['-vvv'])
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Namespace(verbose=3)
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```
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You can also specify an arbitrary `Action` by sub-classing Action. If you want
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to do this, you must `import argparse` in your plugin.
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More info on that is available [here](https://docs.python.org/3/library/argparse.html#action).
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##### Type Constraints
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If you want an argument to be of a certain type, you can include a `type=TYPE` keyword, done like so.
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```python
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SomeParser.add_argument('argname', type=int)
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```
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As such this will return an error if the input can not be converted to an `int`.
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Types usable are `str` and `int`,
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there may be more that are allowed in this keyword argument,
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but `str` and `int` are the only ones we have throughly used.
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**Note**: TYPE can be technically any callable. More about that [here](https://docs.python.org/3/library/argparse.html#type)!
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##### Choices
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If you want to limit what the user can enter for an argument,
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like if they have to choose something from a pre-existing list.
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This can be used by adding `choices=['A', 'AAAA', 'CNAME']` into the
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`SomeParser.add_argument()` call along with the option entries (-a/--argname).
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```python
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SomeParser.add_argument('argname', choices=['A', 'AAAA', 'CNAME'])
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```
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##### Needed Args (aka. nargs)
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The keyword argument `nargs` or Needed Args associates a different number of arguments to an action.
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* `N` - this is an integer; N arguments will be gathered into a list. nargs=1 produces a list of one item, while the default (not using nargs) produces just the argument itself.
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* `'?'` - One argument will be used. If `default` is defined in the call, then default will be used if there is no given argument.
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* `'*'` - All arguments are gathered into a list. It only makes sense to use this once in a command handler.
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* `'+'` - Like '*' but raises an error if there wasn't at least one argument given.
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* `utils.IRCParser.REMAINDER` - remaining arguments are gathered into a list; this is usually used when you need to get a phrase stored, such as the 'quote' text of a quote, a service bot part reason, etc. This is an alias to `argparse.REMAINDER`.
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