easy-flags 0.2.0

Simplified flags definition.

The goal of this nano-project is to provide simple alternative for argparse by adding some new features:

1. typechecking
2. configuration reusability
3. config print out

Installation

pip install easy_flags

Basic example

configs.py

from easy_flags import BaseConfig

# main config with model parameters
class ModelConfig(BaseConfig):
    layers = 4
    dropout = 0.4, 'this is docstring for this field'  # type: float
    leaky = True, 'use leaky relu'  # type: bool

# extend model config with training flags
class TrainingConfig(ModelConfig):
    lr = 0.001, 'learning rate'  # type: float
    e = 100, 'number of epochs'  # type: int

class PredictConfig(ModelConfig):
    load_path = 'path/to/model/checkpoint'

train.py

from configs import TrainingConfig

conf = TrainingConfig()  # instantiate config object

def train(epochs: int, lr: float, layers: int, dropout: float, leaky_relu: bool):
    # or use `conf` directly inside function
    ...

def main():
    train(conf.e, conf.lr, conf.layers, conf.dropout, conf.leaky)

if __name__ == "__main__":
    conf.define()  # read/parse flags from sys.argv and fill up `conf` with values
    conf.print()  # pretty-print all flags and their values
    main()

python train.py --layers 2 --lr 0.1 -e 42 --no-leaky

predict.py

from configs import PredictConfig

conf = PredictConfig()

def predict(load_path: str, layers: int):
    ...

def main():
    predict(conf.load_path, conf.layers)

if __name__ == "__main__":
    conf.define()
    conf.print()
    main()

python predict.py --layers 2 --load_path "not/default/path/to/model" --no-leaky

Docstrings

If you want to add help message for field (which will be displayed if you run script with --help flag), then you need to add it after flags’ default value:

class ExampleConfig(BaseConfig):
    foo = 5.0, 'Some float field.'
    bar = 'field with only default docstring'

./script.py --help
usage: test_base.py [-h] [--bar BAR] [--foo FOO]

optional arguments:
  -h, --help  show this help message and exit
  --bar BAR   String field, default='field with default docstring'.
  --foo FOO   Float field, default=5.0. Some float field.

Booleans

Boolean flag with spefied in config name will set destination value to True, and the same flag prefixed with ‘no-‘ will set value to False

class ExampleConfig(BaseConfig):
    cache = True
    f = False

./script --cache -f
# cache=True, f=True

./script --no-cache --no-f
# cache=False, f=False

Short flag names

If flag name consists only from one letter then it can be specified with one dash instead of two.

class ExampleConfig(BaseConfig):
    e = 100, 'number of epochs'
    b = True

./train.py -e 42 -b
# also valid with two dashes
./train.py --e 42 --b
./train.py --e 42 --no-b

Specify type for tuples

class ExampleConfig(BaseConfig):
    lr = 0.001, 'learning rate'
conf = ExampleConfig()
conf.define()

In example above pre-defined conf.lr is obviously not a float and some IDE/linters after typechecking will make a warning that they expected a float as argument for some function but got tuple instead. Fortunately we can help IDE by adding special comment with proper after-define type:

class ExampleConfig(BaseConfig):
    lr = 0.001, 'learning rate'  # type: float

Global FLAGS

Globally available easy_flags.FLAGS is pointing to the latest defined config or to None if no config was defined. You can specify type after import:

from easy_flags import FLAGS
from configs import ExampleConfig

FLAGS: ExampleConfig = FLAGS

# or just import config object from script that defines it
from train import conf