Added Buy and Sell support

Added buy_btc and sell_btc functions which buy or sell a specified
quantity of bitcoins through Coinbase. Also added CoinbaseError class
which currently only contains the list of strings returned by the
'errors' index into the response. Tested with api_key.

Author: kroberts

coinbase/__init__.py

@@ -45,7 +45,7 @@
 #from decimal import Decimal
 
 from coinbase.config import COINBASE_ENDPOINT
-from coinbase.models import CoinbaseAmount, CoinbaseTransaction, CoinbaseUser, CoinbaseTransfer
+from coinbase.models import CoinbaseAmount, CoinbaseTransaction, CoinbaseUser, CoinbaseTransfer, CoinbaseError
 
 
 class CoinbaseAccount(object):
@@ -193,6 +193,10 @@ def contacts(self):
         response = self.session.get(url, params=self.global_request_params)
         return [contact['contact'] for contact in response.json()['contacts']]
 
+
+
+
+
     def buy_price(self, qty=1):
         """
         Return the buy price of BitCoin in USD
@@ -225,6 +229,48 @@ def sell_price(self, qty=1):
     #     response = self.session.get(url)
     #     return response.json()
 
+
+    def buy_btc(self, qty, pricevaries=False):
+        """
+        Buy BitCoin from Coinbase for USD
+        :param qty: BitCoin quantity to be bought
+        :param pricevaries: Boolean value that indicates whether or not the transaction should
+                be processed if Coinbase cannot gaurentee the current price. 
+        :return: CoinbaseTransfer with all transfer details on success or 
+                 CoinbaseError with the error list received from Coinbase on failure
+        """
+        url = COINBASE_ENDPOINT + '/buys'
+        request_data = {
+            "qty": qty,
+            "agree_btc_amount_varies": pricevaries
+        }
+        response = self.session.post(url=url, data=json.dumps(request_data), params=self.global_request_params)
+        response_parsed = response.json()
+        if response_parsed['success'] == False:
+            return CoinbaseError(response_parsed['errors'])
+
+        return CoinbaseTransfer(response_parsed['transfer'])
+
+
+    def sell_btc(self, qty):
+        """
+        Sell BitCoin to Coinbase for USD
+        :param qty: BitCoin quantity to be sold
+        :return: CoinbaseTransfer with all transfer details on success or 
+                 CoinbaseError with the error list received from Coinbase on failure
+        """
+        url = COINBASE_ENDPOINT + '/sells'
+        request_data = {
+            "qty": qty,
+        }
+        response = self.session.post(url=url, data=json.dumps(request_data), params=self.global_request_params)
+        response_parsed = response.json()
+        if response_parsed['success'] == False:
+            return CoinbaseError(response_parsed['errors'])
+
+        return CoinbaseTransfer(response_parsed['transfer'])       
+
+
     def request(self, from_email, amount, notes='', currency='BTC'):
         """
         Request BitCoin from an email address to be delivered to this account

coinbase/models/__init__.py

@@ -4,4 +4,5 @@
 from transaction import CoinbaseTransaction
 from transfer import CoinbaseTransfer
 from contact import CoinbaseContact
-from user import CoinbaseUser
+from user import CoinbaseUser
+from error import CoinbaseError

coinbase/models/error.py

@@ -0,0 +1,8 @@
+__author__ = 'kroberts'
+
+
+
+class CoinbaseError(object):
+
+    def __init__(self, errorList):
+        self.error = errorList

coinbase/models/transfer.py

@@ -18,7 +18,7 @@ def __init__(self, transfer):
         self.fees_bank = CoinbaseAmount(fees_bank_cents, fees_bank_currency_iso)
 
         self.payout_date = transfer['payout_date']
-        self.transaction_id = transfer['transaction_id']
+        self.transaction_id = transfer.get('transaction_id','')
         self.status = transfer['status']
 
         btc_amount = transfer['btc']['amount']
@@ -33,7 +33,7 @@ def __init__(self, transfer):
         total_currency = transfer['total']['currency']
         self.total_amount = CoinbaseAmount(total_amount, total_currency)
 
-        self.description = transfer['description']
+        self.description = transfer.get('description','')
 
     def refresh(self):
         pass