add parsing OS env vars (#4022)

* add parsing OS env vars

* fix env

* Apply suggestions from code review

* overwrite init

* Apply suggestions from code review

pytorch_lightning/trainer/connectors/env_vars_connector.py

@@ -0,0 +1,43 @@
+# Copyright The PyTorch Lightning team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from functools import wraps
+from typing import Callable
+
+from pytorch_lightning.utilities.argparse_utils import parse_env_variables, get_init_arguments_and_types
+
+
+def overwrite_by_env_vars(fn: Callable) -> Callable:
+    """
+    Decorator for :class:`~pytorch_lightning.trainer.trainer.Trainer` methods for which
+    input arguments should be moved automatically to the correct device.
+
+    """
+    @wraps(fn)
+    def overwrite_by_env_vars(self, *args, **kwargs):
+        # get the class
+        cls = self.__class__
+        if args:  # inace any args passed move them to kwargs
+            # parse only the argument names
+            cls_arg_names = [arg[0] for arg in get_init_arguments_and_types(cls)]
+            # convert args to kwargs
+            kwargs.update({k: v for k, v in zip(cls_arg_names, args)})
+        # update the kwargs by env variables
+        # todo: maybe add a warning that some init args were overwritten by Env arguments
+        kwargs.update(vars(parse_env_variables(cls)))
+
+        # all args were already moved to kwargs
+        return fn(self, **kwargs)
+
+    return overwrite_by_env_vars

pytorch_lightning/trainer/properties.py

@@ -112,6 +112,10 @@ class TrainerProperties(ABC):
     def parse_argparser(cls, arg_parser: Union[ArgumentParser, Namespace]) -> Namespace:
         return argparse_utils.parse_argparser(cls, arg_parser)
 
+    @classmethod
+    def match_env_arguments(cls) -> Namespace:
+        return argparse_utils.parse_env_variables(cls)
+
     @classmethod
     def add_argparse_args(cls, parent_parser: ArgumentParser) -> ArgumentParser:
         return argparse_utils.add_argparse_args(cls, parent_parser)

pytorch_lightning/trainer/trainer.py

@@ -28,6 +28,7 @@ from pytorch_lightning.loggers import LightningLoggerBase
 from pytorch_lightning.profiler import BaseProfiler
 from pytorch_lightning.trainer.callback_hook import TrainerCallbackHookMixin
 from pytorch_lightning.trainer.configuration_validator import ConfigValidator
+from pytorch_lightning.trainer.connectors.env_vars_connector import overwrite_by_env_vars
 from pytorch_lightning.trainer.data_loading import TrainerDataLoadingMixin
 from pytorch_lightning.trainer.logging import TrainerLoggingMixin
 from pytorch_lightning.trainer.model_hooks import TrainerModelHooksMixin
@@ -79,6 +80,7 @@ class Trainer(
     TrainerTrainingTricksMixin,
     TrainerDataLoadingMixin,
 ):
+    @overwrite_by_env_vars
     def __init__(
         self,
         logger: Union[LightningLoggerBase, Iterable[LightningLoggerBase], bool] = True,

pytorch_lightning/utilities/argparse_utils.py

@@ -1,4 +1,5 @@
 import inspect
+import os
 from argparse import ArgumentParser, Namespace
 from typing import Union, List, Tuple, Any
 from pytorch_lightning.utilities import parsing
@@ -7,6 +8,7 @@ from pytorch_lightning.utilities import parsing
 def from_argparse_args(cls, args: Union[Namespace, ArgumentParser], **kwargs):
     """
     Create an instance from CLI arguments.
+    Eventually use varibles from OS environement which are defined as "PL_<CLASS-NAME>_<CLASS_ARUMENT_NAME>"
 
     Args:
         args: The parser or namespace to take arguments from. Only known arguments will be
@@ -22,8 +24,11 @@ def from_argparse_args(cls, args: Union[Namespace, ArgumentParser], **kwargs):
         >>> args = Trainer.parse_argparser(parser.parse_args(""))
         >>> trainer = Trainer.from_argparse_args(args, logger=False)
     """
+    # fist check if any args are defined in environment for the class and set as default
+
     if isinstance(args, ArgumentParser):
         args = cls.parse_argparser(args)
+    # if other arg passed,  update parameters
     params = vars(args)
 
     # we only want to pass in valid Trainer args, the rest may be user specific
@@ -61,6 +66,35 @@ def parse_argparser(cls, arg_parser: Union[ArgumentParser, Namespace]) -> Namesp
     return Namespace(**modified_args)
 
 
+def parse_env_variables(cls, template: str = "PL_%(cls_name)s_%(cls_argument)s") -> Namespace:
+    """Parse environment arguments if they are defined.
+
+    Example:
+        >>> from pytorch_lightning import Trainer
+        >>> parse_env_variables(Trainer)
+        Namespace()
+        >>> import os
+        >>> os.environ["PL_TRAINER_GPUS"] = '42'
+        >>> os.environ["PL_TRAINER_BLABLABLA"] = '1.23'
+        >>> parse_env_variables(Trainer)
+        Namespace(gpus=42)
+        >>> del os.environ["PL_TRAINER_GPUS"]
+    """
+    cls_arg_defaults = get_init_arguments_and_types(cls)
+
+    env_args = {}
+    for arg_name, _, _ in cls_arg_defaults:
+        env = template % {'cls_name': cls.__name__.upper(), 'cls_argument': arg_name.upper()}
+        val = os.environ.get(env)
+        if not (val is None or val == ''):
+            try:  # converting to native types like int/float/bool
+                val = eval(val)
+            except Exception:
+                pass
+            env_args[arg_name] = val
+    return Namespace(**env_args)
+
+
 def get_init_arguments_and_types(cls) -> List[Tuple[str, Tuple, Any]]:
     r"""Scans the Trainer signature and returns argument names, types and default values.
 

tests/trainer/flags/test_env_vars.py

@@ -0,0 +1,28 @@
+import os
+
+from pytorch_lightning import Trainer
+
+
+def test_passing_env_variables(tmpdir):
+    """Testing overwriting trainer arguments """
+    trainer = Trainer()
+    assert trainer.logger is not None
+    assert trainer.max_steps is None
+    trainer = Trainer(False, max_steps=42)
+    assert trainer.logger is None
+    assert trainer.max_steps == 42
+
+    os.environ['PL_TRAINER_LOGGER'] = 'False'
+    os.environ['PL_TRAINER_MAX_STEPS'] = '7'
+    trainer = Trainer()
+    assert trainer.logger is None
+    assert trainer.max_steps == 7
+
+    os.environ['PL_TRAINER_LOGGER'] = 'True'
+    trainer = Trainer(False, max_steps=42)
+    assert trainer.logger is not None
+    assert trainer.max_steps == 7
+
+    # this has to be cleaned
+    del os.environ['PL_TRAINER_LOGGER']
+    del os.environ['PL_TRAINER_MAX_STEPS']