init: add read_key() convenience

Currently the data link library allows users to define a simple
credential file where the api key is anticipated, but requires an
explicit call to read_key().  Introduce convenience logic to set the api
key in global configuration, if the file exist.

Update documentation in support of read_key() convenience.

Signed-off-by: Jamie Couture <[email protected]>

README.md

@@ -38,29 +38,23 @@ nasdaqdatalink.ApiConfig.verify_ssl = False
 
 ### Local API Key file
 
-The default configuration file location is `~/.nasdaq/data_link_apikey`.
+The default configuration file location is `~/.nasdaq/data_link_apikey`.  The
+client will attempt to load this file if it exists.  Note: if the file exists
+and empty, a ValueError will be thrown.
 
-Save api key locally:
+Save your api key locally:
 ```
 import nasdaqdatalink
 nasdaqdatalink.save_key("supersecret")
 print(nasdaqdatalink.ApiConfig.api_key)
 ```
 
-Load the API Key without exposing the key in the script or notebook
-
-```
-import nasdaqdatalink
-nasdaqdatalink.read_key()
-print(nasdaqdatalink.ApiConfig.api_key)
-```
-
-Set a custom location for the API key file, e.g. store the externally outside a docker container
+Set a custom location for the API key file:
 ```
 import nasdaqdatalink
 nasdaqdatalink.save_key("ourcorporateapikey", filename="/srv/data/somecontainer/.corporatenasdaqdatalinkapikey")
 ```
-and call within the docker container with mount point at `/data`
+Requires an explicit read_key() call with the absolute path:
 ```
 import nasdaqdatalink
 nasdaqdatalink.read_key(filepath="/data/.corporatenasdaqdatalinkapikey")

nasdaqdatalink/__init__.py

@@ -15,3 +15,7 @@
 from .export_table import export_table
 from .get_table import get_table
 from .get_point_in_time import get_point_in_time
+
+
+if api_config.default_config_file_exists():
+    read_key()

nasdaqdatalink/api_config.py

@@ -36,6 +36,11 @@ def default_config_filename():
     return os.path.expanduser(config_file)
 
 
+def default_config_file_exists():
+    config_filename = default_config_filename()
+    return os.path.isfile(config_filename)
+
+
 def save_key(apikey, filename=None):
     if filename is None:
         filename = default_config_filename()