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First steps

Basic usage

To parse command line arguments in the simplest possible way create class that is inheriting after RocketBase. Then for every CLI argument that you want to add, create class field with appropriate type hint:

class MyArgs(RocketBase):
    my_int: int  # for CLI argument --my-int
    my_float: float  # for CLI argument --my-float
    my_str: str  # for CLI argument --my-str

Note

You must provide type hints for class fields so they can be correctly parsed.

Then what you need is to call parse_args() method on class (not instance!) to let all CLI parsing magic happen:

args = MyArgs.parse_args()

Now you can access all fields defined above:

print(args.my_int, args.my_float, args.my_str)

---

Put all above code into some file - let's say main.py:

from rocket_args import RocketBase

class MyArgs(RocketBase):
    my_int: int
    my_float: float
    my_str: str

args = MyArgs.parse_args()
print(args.my_int, args.my_float, args.my_str)

And launch it with arguments:

$ python main.py --my-int 1234 --my-float 12.34 --my-str abcd
1234 12.34 abcd

Also, all arguments specified in class are required - when you don't provide any of them you will get following message:

$ python main.py
usage: scratch.py [-h] --my-int MY_INT --my-float MY_FLOAT --my-str MY_STR
scratch.py: error: the following arguments are required: --my-int, --my-float, --my-str

Pretty-printing CLI arguments

To reduce amount of boilerplate code print your arguments instance directly:

from rocket_args import RocketBase

class MyArgs(RocketBase):
    my_int: int
    my_float: float
    my_str: str

args = MyArgs.parse_args()
print(args)

Now launch it:

$ python main.py --my-int 1234 --my-float 12.34 --my-str abcd
MyArgs(my_int=1234, my_float=12.34, my_str=abcd)

Default values

You can specify default values for your fields:

from rocket_args import RocketBase

class MyArgs(RocketBase):
    my_int: int = 123
    my_float: float = 12.34
    my_str: str = "abcd"

args = MyArgs.parse_args()
print(args)

Every CLI argument whose class field has default value assigned doesn't have to be provided from command line. So launching above script without CLI arguments will work:

$ python main.py
MyArgs(my_int=1234, my_float=12.34, my_str=abcd)

Of course you can overwrite them by providing arguments from command line:

$ python main.py --my-int 5678 --my-float 56.78 --my-str efgh
MyArgs(my_int=5678, my_float=56.78, my_str=efgh)

Help

When you launch above script with --help parameter you will get help message:

$ python main.py --help
usage: main.py [-h] [--my-int MY_INT] [--my-float MY_FLOAT] [--my-str MY_STR]

optional arguments:
  -h, --help           show this help message and exit
  --my-int MY_INT
  --my-float MY_FLOAT
  --my-str MY_STR

Generated CLI argument names

For every class field there will be generated CLI argument following these steps:

1. All underscores will be changed to dashes.
2. Two leading dashes will be added.

For example:

• field arg -> CLI argument --arg
• field long_arg_name -> CLI argument --long-arg-name