Prepare for Python3 compatibility [3]

Summary:
A couple small issues pointed out by Ross.

 - Treating bytes as strings with a subprocess' output :/
 - Controling precision of logged floats using a workaround instead of
   FLOAT_REPR which doesn't work with newer versions of Python3.

Reviewed By: rbgirshick

Differential Revision: D9724292

fbshipit-source-id: a6aa1730f25df5d165291dc30b9350a9fff6fca6

detectron/datasets/json_dataset_evaluator.py

@@ -24,6 +24,7 @@ import json
 import logging
 import numpy as np
 import os
+import six
 import uuid
 
 from pycocotools.cocoeval import COCOeval
@@ -86,6 +87,16 @@ def _write_coco_segms_results_file(
         'Writing segmentation results json to: {}'.format(
             os.path.abspath(res_file)))
     with open(res_file, 'w') as fid:
+        # "counts" is an array encoded by mask_util as a byte-stream. Python3's
+        # json writer which /always produces strings/ cannot serialize a bytestream
+        # unless you decode it. Thankfully, utf-8 works out (which is also what
+        # the pycocotools/_mask.pyx does.
+        if six.PY3:
+            for r in results:
+                rle = r['segmentation']
+                if 'counts' in rle:
+                    rle['counts'] = rle['counts'].decode("utf8")
+
         json.dump(results, fid)
 
 

detectron/utils/c2.py

@@ -160,6 +160,7 @@ def get_nvidia_info():
 def get_nvidia_smi_output():
     try:
         info = subprocess.check_output(["nvidia-smi"], stderr=subprocess.STDOUT)
+        info = info.decode("utf8")
     except Exception as e:
         info = "Executing nvidia-smi failed: " + str(e)
     return info.strip()

detectron/utils/logging.py

@@ -28,11 +28,13 @@ import numpy as np
 import smtplib
 import sys
 
-# Print lower precision floating point values than default FLOAT_REPR
-json.encoder.FLOAT_REPR = lambda o: format(o, '.6f')
-
 
 def log_json_stats(stats, sort_keys=True):
+    # hack to control precision of top-level floats
+    stats = {
+        k: '{:.6f}'.format(v) if isinstance(v, float) else v
+        for k, v in stats.items()
+    }
     print('json_stats: {:s}'.format(json.dumps(stats, sort_keys=sort_keys)))
 
 

detectron/utils/subprocess.py

@@ -93,7 +93,7 @@ def process_in_parallel(
     outputs = []
     for i, p, start, end, subprocess_stdout in processes:
         log_subprocess_output(i, p, output_dir, tag, start, end)
-        if isinstance(subprocess_stdout, file):  # NOQA (Python 2 for now)
+        if i > 0:
             subprocess_stdout.close()
         range_file = os.path.join(
             output_dir, '%s_range_%s_%s.pkl' % (tag, start, end)
@@ -119,10 +119,10 @@ def log_subprocess_output(i, p, output_dir, tag, start, end):
     logger.info('# ' + '-' * 76 + ' #')
     if i == 0:
         # Stream the piped stdout from the first subprocess in realtime
-        with open(outfile, 'w') as f:
+        with open(outfile, 'wb') as f:
             for line in iter(p.stdout.readline, b''):
-                print(line.rstrip())
-                f.write(str(line))
+                print(line.rstrip().decode("utf8"))
+                f.write(line)
         p.stdout.close()
         ret = p.wait()
     else: