diff --git a/.travis.yml b/.travis.yml
index 80ea1302990d..7da52e98080d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,5 @@
 language: python
-python: 3.7
+python: 3.8
 cache: pip
 before_install: pip install --upgrade pip setuptools
 install: pip install -r requirements.txt
diff --git a/data_structures/linked_list/deque_doubly.py b/data_structures/linked_list/deque_doubly.py
index d858333220e9..abc7bc1f769f 100644
--- a/data_structures/linked_list/deque_doubly.py
+++ b/data_structures/linked_list/deque_doubly.py
@@ -7,31 +7,36 @@
     4. remove from the end -> O(1)
 """
 
+
 class _DoublyLinkedBase:
     """ A Private class (to be inherited) """
+
     class _Node:
-        __slots__ = '_prev', '_data', '_next'
+        __slots__ = "_prev", "_data", "_next"
+
         def __init__(self, link_p, element, link_n):
             self._prev = link_p
             self._data = element
             self._next = link_n
-        
+
         def has_next_and_prev(self):
-            return " Prev -> {0}, Next -> {1}".format(self._prev != None, self._next != None)
-    
+            return " Prev -> {0}, Next -> {1}".format(
+                self._prev != None, self._next != None
+            )
+
     def __init__(self):
         self._header = self._Node(None, None, None)
         self._trailer = self._Node(None, None, None)
         self._header._next = self._trailer
         self._trailer._prev = self._header
         self._size = 0
-    
+
     def __len__(self):
         return self._size
-    
+
     def is_empty(self):
         return self.__len__() == 0
-    
+
     def _insert(self, predecessor, e, successor):
         # Create new_node by setting it's prev.link -> header
         # setting it's next.link -> trailer
@@ -40,11 +45,11 @@ def _insert(self, predecessor, e, successor):
         successor._prev = new_node
         self._size += 1
         return self
-    
+
     def _delete(self, node):
         predecessor = node._prev
         successor = node._next
-        
+
         predecessor._next = successor
         successor._prev = predecessor
         self._size -= 1
@@ -53,8 +58,8 @@ def _delete(self, node):
         del node
         return temp
 
+
 class LinkedDeque(_DoublyLinkedBase):
-    
     def first(self):
         """ return first element 
         >>> d = LinkedDeque()
@@ -62,11 +67,11 @@ def first(self):
         'A'
         >>> d.add_first('B').first()
         'B'
-        """ 
+        """
         if self.is_empty():
-            raise Exception('List is empty')
+            raise Exception("List is empty")
         return self._header._next._data
-    
+
     def last(self):
         """ return last element
         >>> d = LinkedDeque()
@@ -76,27 +81,27 @@ def last(self):
         'B'
         """
         if self.is_empty():
-            raise Exception('List is empty')
+            raise Exception("List is empty")
         return self._trailer._prev._data
-    
+
     ### DEque Insert Operations (At the front, At the end) ###
-    
+
     def add_first(self, element):
         """ insertion in the front
         >>> LinkedDeque().add_first('AV').first()
         'AV'
         """
         return self._insert(self._header, element, self._header._next)
-    
+
     def add_last(self, element):
         """ insertion in the end
         >>> LinkedDeque().add_last('B').last()
         'B'
         """
         return self._insert(self._trailer._prev, element, self._trailer)
-    
+
     ### DEqueu Remove Operations (At the front, At the end) ###
-    
+
     def remove_first(self):
         """ removal from the front
         >>> d = LinkedDeque()
@@ -114,9 +119,9 @@ def remove_first(self):
         True
         """
         if self.is_empty():
-            raise IndexError('remove_first from empty list')
+            raise IndexError("remove_first from empty list")
         return self._delete(self._header._next)
-    
+
     def remove_last(self):
         """ removal in the end
         >>> d = LinkedDeque()
@@ -134,5 +139,5 @@ def remove_last(self):
         True
         """
         if self.is_empty():
-            raise IndexError('remove_first from empty list')
+            raise IndexError("remove_first from empty list")
         return self._delete(self._trailer._prev)
diff --git a/requirements.txt b/requirements.txt
index 2c4ac59d3e09..16fca79cfcec 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,7 +4,7 @@ fake_useragent
 flake8
 matplotlib
 mypy
-numpy>=1.17.4
+numpy>=1.18.1
 opencv-python
 pandas
 pillow
@@ -14,4 +14,4 @@ requests
 scikit-fuzzy
 sklearn
 sympy
-tensorflow
+tensorflow==2.1.0rc2
diff --git a/sorts/recursive_bubble_sort.py b/sorts/recursive_bubble_sort.py
index 88c13cbb95b5..616044778a4a 100644
--- a/sorts/recursive_bubble_sort.py
+++ b/sorts/recursive_bubble_sort.py
@@ -24,17 +24,18 @@ def bubble_sort(list1):
     
     """
 
-    for i, num in enumerate(list1): 
-        try: 
-            if list1[i+1] < num: 
-                list1[i] = list1[i+1] 
-                list1[i+1] = num 
-                bubble_sort(list1) 
-        except IndexError: 
+    for i, num in enumerate(list1):
+        try:
+            if list1[i + 1] < num:
+                list1[i] = list1[i + 1]
+                list1[i + 1] = num
+                bubble_sort(list1)
+        except IndexError:
             pass
-    return list1 
+    return list1
 
-if __name__ == "__main__":     
-    list1 = [33,99,22,11,66]    
-    bubble_sort(list1)     
+
+if __name__ == "__main__":
+    list1 = [33, 99, 22, 11, 66]
+    bubble_sort(list1)
     print(list1)