Fixed PYTHONPATH for ddp test model (#4528)

* Fixed PYTHONPATH for ddp test model

* Removed debug calls

* Apply suggestions from code review

Co-authored-by: Jirka Borovec <Borda@users.noreply.github.com>
Co-authored-by: chaton <thomas@grid.ai>
Co-authored-by: Sean Naren <sean.narenthiran@gmail.com>

tests/backends/ddp_model.py

@@ -14,20 +14,24 @@
 """
 Runs either `.fit()` or `.test()` on a single node across multiple gpus.
 """
+import os
 from argparse import ArgumentParser
 
+import tests as pl_tests
 from pytorch_lightning import Trainer, seed_everything
 from tests.base import EvalModelTemplate
-import os
+
 import torch
 
 
 def main():
     seed_everything(1234)
+
     parser = ArgumentParser(add_help=False)
     parser = Trainer.add_argparse_args(parser)
     parser.add_argument('--trainer_method', default='fit')
     parser.add_argument('--tmpdir')
+    parser.add_argument('--workdir')
     parser.set_defaults(gpus=2)
     parser.set_defaults(distributed_backend="ddp")
     args = parser.parse_args()
@@ -38,14 +42,26 @@ def main():
     result = {}
     if args.trainer_method == 'fit':
         trainer.fit(model)
-        result = {'status': 'complete', 'method': args.trainer_method, 'result': None}
+        result = {
+            'status': 'complete',
+            'method': args.trainer_method,
+            'result': None
+        }
     if args.trainer_method == 'test':
         result = trainer.test(model)
-        result = {'status': 'complete', 'method': args.trainer_method, 'result': result}
+        result = {
+            'status': 'complete',
+            'method': args.trainer_method,
+            'result': result
+        }
     if args.trainer_method == 'fit_test':
         trainer.fit(model)
         result = trainer.test(model)
-        result = {'status': 'complete', 'method': args.trainer_method, 'result': result}
+        result = {
+            'status': 'complete',
+            'method': args.trainer_method,
+            'result': result
+        }
 
     if len(result) > 0:
         file_path = os.path.join(args.tmpdir, 'ddp.result')

tests/utilities/distributed.py

@@ -29,11 +29,10 @@ def call_training_script(module_file, cli_args, method, tmpdir, timeout=60):
 
     # need to set the PYTHONPATH in case pytorch_lightning was not installed into the environment
     env = os.environ.copy()
-    env['PYTHONPATH'] = f'{pytorch_lightning.__file__}:' + env.get('PYTHONPATH', '')
+    env['PYTHONPATH'] = env.get('PYTHONPATH', '') + f'{pytorch_lightning.__file__}:'
 
     # for running in ddp mode, we need to lauch it's own process or pytest will get stuck
     p = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, env=env)
-
     try:
         std, err = p.communicate(timeout=timeout)
         err = str(err.decode("utf-8"))
@@ -42,5 +41,4 @@ def call_training_script(module_file, cli_args, method, tmpdir, timeout=60):
     except TimeoutExpired:
         p.kill()
         std, err = p.communicate()
-
     return std, err