Issue 116 - Save and read API Key from local file

README.md

@@ -37,6 +37,34 @@ quandl.ApiConfig.api_version = '2015-04-09'
 
 `quandl.ApiConfig.api_version` is optional however it is strongly recommended to avoid issues with rate-limiting. For premium databases, datasets and datatables `quandl.ApiConfig.api_key` will need to be set to identify you to our API. Please see [API Documentation](https://www.quandl.com/docs/api) for more detail.
 
+
+### Local API Key file
+Save local key to `$HOME/.quandl_apikey` file
+```
+import quandl
+quandl.save_key("supersecret")
+print(quandl.ApiConfig.api_key)
+```
+
+Load the API Key without exposing the key in the script or notebook
+```
+import quandl
+quandl.read_key()
+print(quandl.ApiConfig.api_key)
+```
+
+Set a custom location for the API key file, e.g. store the externally outside a docker container
+```
+import quandl
+quandl.save_key("ourcorporateapikey", filename="/srv/data/somecontainer/.corporatequandlapikey")
+```
+and call within the docker container with mount point at `/data`
+```
+import quandl
+quandl.read_key(filepath="/data/.corporatequandlapikey")
+```
+
+
 ## Retrieving Data
 
 There are two methods for retrieving data in Python: the Quick method and the Detailed method. The latter is more suitable to application programming. Both methods work with Quandl's two types of data structures: time-series (dataset) data and non-time series (datatable).

quandl/__init__.py

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-from .api_config import ApiConfig
+from .api_config import ApiConfig, save_key, read_key
 
 from .errors.quandl_error import *
 

quandl/api_config.py

@@ -3,3 +3,32 @@ class ApiConfig:
     api_base = 'https://www.quandl.com/api/v3'
     api_version = None
     page_limit = 100
+
+
+def save_key(apikey, filename=None):
+    if filename is None:
+        import pathlib
+        filename = str(pathlib.Path.home()) + "/.quandl_apikey"
+
+    fileptr = open(filename, 'w')
+    fileptr.write(apikey)
+    fileptr.close()
+    ApiConfig.api_key = apikey
+
+
+def read_key(filename=None):
+    if filename is None:
+        import pathlib
+        filename = str(pathlib.Path.home()) + "/.quandl_apikey"
+
+    try:
+        fileptr = open(filename, 'r')
+        apikey = fileptr.read()
+        fileptr.close()
+
+        if apikey:
+            ApiConfig.api_key = apikey
+        else:
+            raise Exception("File '{:s}' is empty.".format(filename))
+    except ValueError:
+        raise Exception("File '{:s}' not found.".format(filename))