Reflects @aanand's feedback.

docker/utils/__init__.py

@@ -2,7 +2,7 @@
     compare_version, convert_port_bindings, convert_volume_binds,
     mkbuildcontext, tar, parse_repository_tag, parse_host,
     kwargs_from_env, convert_filters, create_host_config,
-    create_container_config, parse_bytes, ping_registry
+    create_container_config, parse_bytes, ping_registry, parse_env_file
 ) # flake8: noqa
 
 from .types import Ulimit, LogConfig # flake8: noqa

docker/utils/utils.py

@@ -519,13 +519,32 @@ def create_host_config(
     return host_config
 
 
+def parse_env_file(env_file):
+    """
+    Reads a line-separated environment file.
+    The format of each line should be "key=value".
+    """
+    environment = []
+
+    if isinstance(env_file, str):
+        if os.path.isfile(env_file):
+            with open(env_file, 'r') as f:
+                for line in csv.reader(f, delimiter='='):
+                    if len(line) == 2:
+                        k = line[0].strip()
+                        v = line[1].strip()
+                        environment.append('{0}={1}'.format(k, v))
+
+    return environment
+
+
 def create_container_config(
     version, image, command, hostname=None, user=None, detach=False,
     stdin_open=False, tty=False, mem_limit=None, ports=None, environment=None,
     dns=None, volumes=None, volumes_from=None, network_disabled=False,
     entrypoint=None, cpu_shares=None, working_dir=None, domainname=None,
     memswap_limit=None, cpuset=None, host_config=None, mac_address=None,
-    labels=None, volume_driver=None, env_file=None
+    labels=None, volume_driver=None
 ):
     if isinstance(command, six.string_types):
         command = shlex.split(str(command))
@@ -536,24 +555,6 @@ def create_container_config(
             for k, v in six.iteritems(environment)
         ]
 
-    if isinstance(env_file, str):
-        if os.path.isfile(env_file):
-
-            # Re-classify None to list if needed
-            if isinstance(environment, type(None)):
-                environment = []
-
-            # Re-classify string to list if needed
-            if isinstance(environment, str):
-                environment = environment.split(',')
-
-            with open(env_file, 'r') as f:
-                for line in csv.reader(f, delimiter='='):
-                    if len(line) == 2:
-                        k = line[0].strip()
-                        v = line[1].strip()
-                        environment.append('{0}={1}'.format(k, v))
-
     if labels is not None and compare_version('1.18', version) < 0:
         raise errors.InvalidVersion(
             'labels were only introduced in API version 1.18'

docs/api.md

@@ -207,11 +207,6 @@ where unit = b, k, m, or g)
 * ports (list of ints): A list of port numbers
 * environment (dict or list): A dictionary or a list of strings in the
 following format `["PASSWORD=xxx"]` or `{"PASSWORD": "xxx"}`.
-* env_file (file): A line-separated list of environment variables, such as:
-```
-USERNAME=jdoe
-PASSWORD=secret
-```
 * dns (list): DNS name servers
 * volumes (str or list):
 * volumes_from (str or list): List of container names or Ids to get volumes
@@ -239,6 +234,27 @@ from. Optionally a single string joining container id's with commas
  'Warnings': None}
 ```
 
+### parse_env_file
+
+A utility for parsing an environment file.
+
+The expected format of the file is as follows:
+
+```
+USERNAME=jdoe
+PASSWORD=secret
+```
+
+The utility can be used as follows:
+
+```python
+>> import docker.utils
+>> my_envs = docker.utils.parse_env_file('/path/to/file')
+>> docker.utils.create_container_config('1.18', '_mongodb', 'foobar',  environment=my_envs)
+```
+
+You can now use this with 'environment' for `create_container`.
+
 ## diff
 
 Inspect changes on a container's filesystem