Metadata-Version: 2.1
Name: typed-argument-parser
Version: 1.7.2
Summary: Typed Argument Parser
Home-page: https://github.com/swansonk14/typed-argument-parser
Author: Jesse Michel and Kyle Swanson
Author-email: jessem.michel@gmail.com, swansonk.14@gmail.com
License: MIT
Download-URL: https://github.com/swansonk14/typed-argument-parser/archive/refs/tags/v_1.7.2.tar.gz
Keywords: typing,argument parser,python
Platform: UNKNOWN
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.6
Classifier: Programming Language :: Python :: 3.7
Classifier: Programming Language :: Python :: 3.8
Classifier: Programming Language :: Python :: 3.9
Classifier: Programming Language :: Python :: 3.10
Classifier: License :: OSI Approved :: MIT License
Classifier: Operating System :: OS Independent
Classifier: Typing :: Typed
Description-Content-Type: text/markdown
License-File: LICENSE.txt

<p align="center">
   <img src="images/logo.png" width="40%" align="middle">
</p>

# Typed Argument Parser (Tap)

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Tap is a typed modernization of Python's [argparse](https://docs.python.org/3/library/argparse.html) library.

Tap provides the following benefits:
- Static type checking
- Code completion
- Source code navigation (e.g. go to definition and go to implementation)

![Tap](https://github.com/swansonk14/typed-argument-parser/raw/main/images/tap.png)

See [this poster](https://docs.google.com/presentation/d/1AirN6gpiq4P1L8K003EsXmobVxP3A4AVEIR2KOEQN7Y/edit?usp=sharing), which we presented at [PyCon 2020](https://us.pycon.org/2020/), for a presentation of some of the relevant concepts we used to guide the development of Tap. 

## Installation

Tap requires Python 3.6+

To install Tap from PyPI run: 
```
pip install typed-argument-parser
```

To install Tap from source, run the following commands:

```
git clone https://github.com/swansonk14/typed-argument-parser.git
cd typed-argument-parser
pip install -e .
```

## Table of Contents

* [Installation](#installation)
* [Table of Contents](#table-of-contents)
* [Tap is Python-native](#tap-is-python-native)
* [Tap features](#tap-features)
  + [Arguments](#arguments)
  + [Help string](#help-string)
  + [Flexibility of `configure`](#flexibility-of--configure-)
    - [Adding special argument behavior](#adding-special-argument-behavior)
    - [Adding subparsers](#adding-subparsers)
  + [Types](#types)
    - [`str`, `int`, and `float`](#-str----int---and--float-)
    - [`bool`](#-bool-)
    - [`Optional`](#-optional-)
    - [`List`](#-list-)
    - [`Set`](#-set-)
    - [`Tuple`](#-tuple-)
    - [`Literal`](#-literal-)
    - [`Union`](#-union-)
    - [Complex Types](#complex-types)
  + [Argument processing with `process_args`](#argument-processing-with--process-args-)
  + [Processing known args](#processing-known-args)
  + [Subclassing](#subclassing)
  + [Printing](#printing)
  + [Reproducibility](#reproducibility)
    - [Reproducibility info](#reproducibility-info)
  + [Saving and loading arguments](#saving-and-loading-arguments)
    - [Save](#save)
    - [Load](#load)
    - [Load from dict](#load-from-dict)
  + [Loading from configuration files](#loading-from-configuration-files)

## Tap is Python-native

To see this, let's look at an example:

```python
"""main.py"""

from tap import Tap

class SimpleArgumentParser(Tap):
    name: str  # Your name
    language: str = 'Python'  # Programming language
    package: str = 'Tap'  # Package name
    stars: int  # Number of stars
    max_stars: int = 5  # Maximum stars

args = SimpleArgumentParser().parse_args()

print(f'My name is {args.name} and I give the {args.language} package '
      f'{args.package} {args.stars}/{args.max_stars} stars!')
```

You use Tap the same way you use standard argparse.

```
>>> python main.py --name Jesse --stars 5
My name is Jesse and I give the Python package Tap 5/5 stars!
```

The equivalent argparse code is:
```python
"""main.py"""

from argparse import ArgumentParser

parser = ArgumentParser()
parser.add_argument('--name', type=str, required=True,
                    help='Your name')
parser.add_argument('--language', type=str, default='Python',
                    help='Programming language')
parser.add_argument('--package', type=str, default='Tap',
                    help='Package name')
parser.add_argument('--stars', type=int, required=True,
                    help='Number of stars')
parser.add_argument('--max_stars', type=int, default=5,
                    help='Maximum stars')
args = parser.parse_args()

print(f'My name is {args.name} and I give the {args.language} package '
      f'{args.package} {args.stars}/{args.max_stars} stars!')
```

The advantages of being Python-native include being able to:
- Overwrite convenient built-in methods (e.g. `process_args` ensures consistency among arguments)
- Add custom methods
- Inherit from your own template classes

## Tap features

Now we are going to highlight some of our favorite features and give examples of how they work in practice.

### Arguments

Arguments are specified as class variables defined in a subclass of `Tap`. Variables defined as `name: type` are required arguments while variables defined as `name: type = value` are not required and default to the provided value.

```python
class MyTap(Tap):
    required_arg: str
    default_arg: str = 'default value'
```

### Help string

Single line and/or multiline comments which appear after the argument are automatically parsed into the help string provided when running `python main.py -h`. The type and default values of arguments are also provided in the help string.

```python
"""main.py"""

from tap import Tap

class MyTap(Tap):
    x: float  # What am I?
    pi: float = 3.14  # I'm pi!
    """Pi is my favorite number!"""

args = MyTap().parse_args()
```

Running `python main.py -h` results in the following:

```
>>> python main.py -h
usage: demo.py --x X [--pi PI] [-h]

optional arguments:
  --x X       (float, required) What am I?
  --pi PI     (float, default=3.14) I'm pi! Pi is my favorite number.
  -h, --help  show this help message and exit
```

### Flexibility of `configure`
To specify behavior beyond what can be specified using arguments as class variables, override the `configure` method.
`configure` provides access to advanced argument parsing features such as `add_argument` and `add_subparser`.
Since Tap is a wrapper around argparse, Tap provides all of the same functionality.
We detail these two functions below.

#### Adding special argument behavior
In the `configure` method, call `self.add_argument` just as you would use argparse's `add_argument`. For example,

```python
from tap import Tap

class MyTap(Tap):
    positional_argument: str
    list_of_three_things: List[str]
    argument_with_really_long_name: int

    def configure(self):
        self.add_argument('positional_argument')
        self.add_argument('--list_of_three_things', nargs=3)
        self.add_argument('-arg', '--argument_with_really_long_name')
```

#### Adding subparsers
To add a subparser, override the `configure` method and call `self.add_subparser`. Optionally, to specify keyword arguments (e.g., `help`) to the subparser collection, call `self.add_subparsers`. For example,

```python
class SubparserA(Tap):
    bar: int  # bar help

class SubparserB(Tap):
    baz: Literal['X', 'Y', 'Z']  # baz help

class Args(Tap):
    foo: bool = False  # foo help

    def configure(self):
        self.add_subparsers(help='sub-command help')
        self.add_subparser('a', SubparserA, help='a help')
        self.add_subparser('b', SubparserB, help='b help')
```

### Types

Tap automatically handles all the following types:

```python
str, int, float, bool
Optional, Optional[str], Optional[int], Optional[float], Optional[bool]
List, List[str], List[int], List[float], List[bool]
Set, Set[str], Set[int], Set[float], Set[bool]
Tuple, Tuple[Type1, Type2, etc.], Tuple[Type, ...]  
Literal
```

If you're using Python 3.9+, then you can replace `List` with `list`, `Set` with `set`, and `Tuple` with `tuple`.

Tap also supports `Union`, but this requires additional specification (see [Union](#-union-) section below).

Additionally, any type that can be instantiated with a string argument can be used. For example, in
```python
from pathlib import Path
from tap import Tap

class Args(Tap):
   path: Path

args = Args().parse_args()
```
`args.path` is a `Path` instance containing the string passed in through the command line.

#### `str`, `int`, and `float`

Each is automatically parsed to their respective types, just like argparse.

#### `bool`

If an argument `arg` is specified as `arg: bool` or `arg: bool = False`, then adding the `--arg` flag to the command line will set `arg` to `True`. If `arg` is specified as `arg: bool = True`, then adding `--arg` sets `arg` to `False`.

Note that if the `Tap` instance is created with `explicit_bool=True`, then booleans can be specified on the command line as `--arg True` or `--arg False` rather than `--arg`. Additionally, booleans can be specified by prefixes of `True` and `False` with any capitalization as well as `1` or `0` (e.g. for True, `--arg tRu`, `--arg T`, `--arg 1` all suffice). 

#### `Optional`

These arguments are parsed in exactly the same way as `str`, `int`, `float`, and `bool`. Note bools can be specified using the same rules as above and that `Optional` is equivalent to `Optional[str]`.

#### `List`

If an argument `arg` is a `List`, simply specify the values separated by spaces just as you would with regular argparse. For example, `--arg 1 2 3` parses to `arg = [1, 2, 3]`.

#### `Set`

Identical to `List` but parsed into a set rather than a list.

#### `Tuple`

Tuples can be used to specify a fixed number of arguments with specified types using the syntax `Tuple[Type1, Type2, etc.]` (e.g. `Tuple[str, int, bool, str]`). Tuples with a variable number of arguments are specified by `Tuple[Type, ...]` (e.g. `Tuple[int, ...]`). Note `Tuple` defaults to `Tuple[str, ...]`.

#### `Literal`

Literal is analagous to argparse's [choices](https://docs.python.org/3/library/argparse.html#choices), which specifies the values that an argument can take. For example, if arg can only be one of 'H', 1, False, or 1.0078 then you would specify that `arg: Literal['H', 1, False, 1.0078]`. For instance, `--arg False` assigns arg to False and `--arg True` throws error. The `Literal` type was introduced in Python 3.8 ([PEP 586](https://www.python.org/dev/peps/pep-0586/)) and can be imported with `from typing_extensions import Literal`.

#### `Union`

Union types must include the `type` keyword argument in `add_argument` in order to specify which type to use, as in the example below.

```python
def to_number(string: str) -> Union[float, int]:
    return float(string) if '.' in string else int(string)

class MyTap(Tap):
    number: Union[float, int]

    def configure(self):
        self.add_argument('--number', type=to_number)
```

In Python 3.10+, `Union[Type1, Type2, etc.]` can be replaced with `Type1 | Type2 | etc.`, but the `type` keyword argument must still be provided in `add_argument`.

#### Complex Types

Tap can also support more complex types than the ones specified above. If the desired type is constructed with a single string as input, then the type can be specified directly without additional modifications. For example,

```python
class Person:
    def __init__(self, name: str) -> None:
        self.name = name

class Args(Tap):
    person: Person

args = Args().parse_args('--person Tapper'.split())
print(args.person.name)  # Tapper
```

If the desired type has a more complex constructor, then the `type` keyword argument must be provided in `add_argument`. For example,

```python
class AgedPerson:
    def __init__(self, name: str, age: int) -> None:
        self.name = name
        self.age = age

def to_aged_person(string: str) -> AgedPerson:
    name, age = string.split(',')
    return AgedPerson(name=name, age=int(age))

class Args(Tap):
    aged_person: AgedPerson

    def configure(self) -> None:
        self.add_argument('--aged_person', type=to_aged_person)

args = Args().parse_args('--aged_person Tapper,27'.split())
print(f'{args.aged_person.name} is {args.aged_person.age}')  # Tapper is 27
```


### Argument processing with `process_args`

With complex argument parsing, arguments often end up having interdependencies. This means that it may be necessary to disallow certain combinations of arguments or to modify some arguments based on other arguments.

To handle such cases, simply override `process_args` and add the required logic. `process_args` is automatically called when `parse_args` is called.

```python
class MyTap(Tap):
    package: str
    is_cool: bool
    stars: int

    def process_args(self):
        # Validate arguments
        if self.is_cool and self.stars < 4:
            raise ValueError('Cool packages cannot have fewer than 4 stars')

        # Modify arguments
        if self.package == 'Tap':
            self.is_cool = True
            self.stars = 5
```

### Processing known args

Similar to argparse's `parse_known_args`, Tap is capable of parsing only arguments that it is aware of without raising an error due to additional arguments. This can be done by calling `parse_args` with `known_only=True`. The remaining un-parsed arguments are then available by accessing the `extra_args` field of the Tap object.

```python
class MyTap(Tap):
    package: str

args = MyTap().parse_args(['--package', 'Tap', '--other_arg', 'value'], known_only=True)
print(args.extra_args)  # ['--other_arg', 'value']
```

### Subclassing

It is sometimes useful to define a template Tap and then subclass it for different use cases. Since Tap is a native Python class, inheritance is built-in, making it easy to customize from a template Tap.

In the example below, `StarsTap` and `AwardsTap` inherit the arguments (`package` and `is_cool`) and the methods (`process_args`) from `BaseTap`.

```python
class BaseTap(Tap):
    package: str
    is_cool: bool

    def process_args(self):
        if self.package == 'Tap':
            self.is_cool = True


class StarsTap(BaseTap):
    stars: int


class AwardsTap(BaseTap):
    awards: List[str]
```

### Printing

Tap uses Python's [pretty printer](https://docs.python.org/3/library/pprint.html) to print out arguments in an easy-to-read format.

```python
"""main.py"""

from tap import Tap
from typing import List

class MyTap(Tap):
    package: str
    is_cool: bool = True
    awards: List[str] = ['amazing', 'wow', 'incredible', 'awesome']

args = MyTap().parse_args()
print(args)
```

Running `python main.py --package Tap` results in:

```
>>> python main.py
{'awards': ['amazing', 'wow', 'incredible', 'awesome'],
 'is_cool': True,
 'package': 'Tap'}
```

### Reproducibility

Tap makes reproducibility easy, especially when running code in a git repo.

#### Reproducibility info

Specifically, Tap has a method called `get_reproducibility_info` that returns a dictionary containing all the information necessary to replicate the settings under which the code was run. This dictionary includes:
- Python command
    - The Python command that was used to run the program
    - Ex. `python main.py --package Tap`
- Time
    - The time when the command was run
    - Ex. `Thu Aug 15 00:09:13 2019`
- Git root
    - The root of the git repo containing the code that was run
    - Ex. `/Users/swansonk14/typed-argument-parser`
- Git url
    - The url to the git repo, specifically pointing to the current git hash (i.e. the hash of HEAD in the local repo)
    - Ex. [https://github.com/swansonk14/typed-argument-parser/tree/446cf046631d6bdf7cab6daec93bf7a02ac00998](https://github.com/swansonk14/typed-argument-parser/tree/446cf046631d6bdf7cab6daec93bf7a02ac00998)
- Uncommitted changes
    - Whether there are any uncommitted changes in the git repo (i.e. whether the code is different from the code at the above git hash)
    - Ex. `True` or `False`

### Saving and loading arguments

#### Save

Tap has a method called `save` which saves all arguments, along with the reproducibility info, to a JSON file.

```python
"""main.py"""

from tap import Tap

class MyTap(Tap):
    package: str
    is_cool: bool = True
    stars: int = 5

args = MyTap().parse_args()
args.save('args.json')
```

After running `python main.py --package Tap`, the file `args.json` will contain:

```
{
    "is_cool": true,
    "package": "Tap",
    "reproducibility": {
        "command_line": "python main.py --package Tap",
        "git_has_uncommitted_changes": false,
        "git_root": "/Users/swansonk14/typed-argument-parser",
        "git_url": "https://github.com/swansonk14/typed-argument-parser/tree/446cf046631d6bdf7cab6daec93bf7a02ac00998",
        "time": "Thu Aug 15 00:18:31 2019"
    },
    "stars": 5
}
```

Note: More complex types will be encoded in JSON as a pickle string.

#### Load

Arguments can be loaded from a JSON file rather than parsed from the command line.

```python
"""main.py"""

from tap import Tap

class MyTap(Tap):
    package: str
    is_cool: bool = True
    stars: int = 5

args = MyTap()
args.load('args.json')
```

Note: All required arguments (in this case `package`) must be present in the JSON file if not already set in the Tap object.

#### Load from dict

Arguments can be loaded from a Python dictionary rather than parsed from the command line.

```python
"""main.py"""

from tap import Tap

class MyTap(Tap):
    package: str
    is_cool: bool = True
    stars: int = 5

args = MyTap()
args.from_dict({
    'package': 'Tap',
    'stars': 20
})
```

Note: As with `load`, all required arguments must be present in the dictionary if not already set in the Tap object. All values in the provided dictionary will overwrite values currently in the Tap object.

### Loading from configuration files
Configuration files can be loaded along with arguments with the optional flag `config_files: List[str]`. Arguments passed in from the command line overwrite arguments from the configuration files. Arguments in configuration files that appear later in the list overwrite the arguments in previous configuration files.

For example, if you have the config file `my_config.txt`
```
--arg1 1
--arg2 two
```
then you can write
```python
from tap import Tap

class Args(Tap):
    arg1: int
    arg2: str

args = Args(config_files=['my_config.txt']).parse_args()
```

Config files are parsed using `shlex.split` from the python standard library, which supports shell-style string quoting, as well as line-end comments starting with `#`.

For example, if you have the config file `my_config_shlex.txt`
```
--arg1 21 # Important arg value

# Multi-word quoted string
--arg2 "two three four"
```
then you can write
```python
from tap import Tap

class Args(Tap):
    arg1: int
    arg2: str

args = Args(config_files=['my_config_shlex.txt']).parse_args()
```
to get the resulting `args = {'arg1': 21, 'arg2': 'two three four'}`

The legacy parsing behavior of using standard string split can be re-enabled by passing `legacy_config_parsing=True` to `parse_args`.


