diff --git a/robinhood/robinhood.py b/robinhood/robinhood.py
index cd27ae3..705fb5b 100644
--- a/robinhood/robinhood.py
+++ b/robinhood/robinhood.py
@@ -1,6 +1,7 @@
 import json
 import requests
 import getpass
+import os
 
 session = requests.Session()
 account_url = None
@@ -11,6 +12,8 @@ def oauth(payload):
 
     url = 'https://api.robinhood.com/oauth2/token/'
     r = session.post(url, json=payload)
+    if r.status_code == 500:
+        raise RuntimeError('Missing or incorrect credentials.')
     session.headers.pop('challenge_id', None)
     response = r.json()
 
@@ -27,26 +30,35 @@ def oauth(payload):
     return r
 
 
-def login(username=None, password=None, device_token='c77a7142-cc14-4bc0-a0ea-bdc9a2bf6e68'):
-    """generates OAuth2 bearer token"""
+def login(username: str = None, password: str = None, device_token: str = 'c77a7142-cc14-4bc0-a0ea-bdc9a2bf6e68',
+          bearer_token: str = None, no_input: bool = False) -> str:
+    """generates and returns OAuth2 bearer token"""
     global session
 
-    # check if bearer token exists and is valid
-    with open('tokens.json') as file:
-        try:
-            tokens = json.loads(file.read())
-            if 'bearer_token' in tokens:
-                session.headers['Authorization'] = 'Bearer ' + tokens['bearer_token']
-                if user():
-                    return
-                else:
-                    del session.headers['Authorization']
-        except json.decoder.JSONDecodeError:
-            pass
+    if bearer_token is not None:
+        session.headers['Authorization'] = 'Bearer ' + bearer_token
+        if user():
+            return bearer_token
+        else:
+            print('Invalid/expired bearer token')
+    # check if bearer token exists and is valid. create tokens.json if does not exist.
+    if os.path.isfile('tokens.json'):
+        with open('tokens.json', 'r') as file:
+            try:
+                tokens = json.loads(file.read())
+                if 'bearer_token' in tokens:
+                    bearer_token = tokens['bearer_token']
+                    session.headers['Authorization'] = 'Bearer ' + bearer_token
+                    if user():
+                        return bearer_token
+                    else:
+                        del session.headers['Authorization']
+            except json.decoder.JSONDecodeError:
+                pass
 
-    if username is None:
+    if username is None and not no_input:
         username = input('Enter email or username: ')
-    if password is None:
+    if password is None and not no_input:
         password = getpass.getpass('Enter password: ')
 
     payload = {
@@ -59,13 +71,15 @@ def login(username=None, password=None, device_token='c77a7142-cc14-4bc0-a0ea-bd
 
     r = oauth(payload)
     if r.status_code == 400:
-        if r.json()['detail'] == 'Request blocked, challenge type required.':
+        r = r.json()
+        if 'detail' in r and r['detail'] == 'Request blocked, challenge type required.':
             challenge_type = None
             while challenge_type not in ['1', '2']:
                 print('Unfamiliar device detected.')
-                challenge_type = input("We're sending you a code to verify your login. Do you want us to:\n"
-                                       "  1: Text you the code\n"
-                                       "  2: Email it to you?\n")
+                challenge_type = '1' if no_input else \
+                    input("We're sending you a code to verify your login. Do you want us to:\n"
+                          "  1: Text you the code\n"
+                          "  2: Email it to you?\n")
                 if challenge_type == '1':
                     print('Texting...')
                     payload['challenge_type'] = 'sms'
@@ -94,10 +108,11 @@ def login(username=None, password=None, device_token='c77a7142-cc14-4bc0-a0ea-bd
             del session.headers['X-ROBINHOOD-CHALLENGE-RESPONSE-ID']
         else:
             raise RuntimeError('Unable to log in with provided credentials.')
-    user()
+
+    return r.json()['access_token']
 
 
-def user():
+def user() -> bool:
     """checks whether user is logged in"""
     url = "https://api.robinhood.com/user/"
     r = session.get(url)
diff --git a/setup.py b/setup.py
index a15446e..eb85adb 100644
--- a/setup.py
+++ b/setup.py
@@ -8,7 +8,7 @@
     description="the unofficial Robinhood API",
     long_description=long_description,
     long_description_content_type="text/markdown",
-    version="0.0.3",
+    version="0.0.4",
     url="https://github.com/james-yun/robinhood",
     author="James Yun",
     author_email="jameswyun99@gmail.com",