Avoid os.makedirs race condition.

changes.md

@@ -1,6 +1,7 @@
 ## v0.1.16 - 2017-07-07
 
 - Translate RuntimeError of older versions of the netCDF4 library to IOError.
+- Avoid race conditions when creating directories for new files.
 
 ## v0.1.15 - 2017-06-20
 

pynetcf/base.py

@@ -33,6 +33,7 @@
 """
 
 import os
+import time
 import numpy as np
 import netCDF4
 import datetime
@@ -108,9 +109,7 @@ def __init__(self, filename, name=None, file_format="NETCDF4",
         if self.mode == "a" and not os.path.exists(self.filename):
             self.mode = "w"
         if self.mode == 'w':
-            path = os.path.dirname(self.filename)
-            if not os.path.exists(path):
-                os.makedirs(path)
+            self._create_file_dir()
 
         try:
             self.dataset = netCDF4.Dataset(self.filename, self.mode,
@@ -121,6 +120,20 @@ def __init__(self, filename, name=None, file_format="NETCDF4",
         self.dataset.set_auto_scale(self.autoscale)
         self.dataset.set_auto_mask(self.automask)
 
+    def _create_file_dir(self):
+        """
+        Create directory for file to sit in.
+        Avoid race condition if multiple instances are
+        writing files into the same directory.
+        """
+        path = os.path.dirname(self.filename)
+        if not os.path.exists(path):
+            try:
+                os.makedirs(path)
+            except OSError:
+                time.sleep(1)
+                self._create_file_dir()
+
     def _set_global_attr(self):
         """
         Write global attributes to NetCDF file.