diff --git a/README.md b/README.md
index 7fc4f0f0b..106f5907e 100644
--- a/README.md
+++ b/README.md
@@ -18,7 +18,7 @@ Read our [Contribution Guidelines](CONTRIBUTING.md) before you contribute.
 
 ## Community Channel
 
-We're on [Gitter](https://gitter.im/TheAlgorithms)! Please join us.
+We're on [Gitter](https://gitter.im/TheAlgorithms)!  Please join us.
 
 ## List of Algorithms
 
diff --git a/data_structures/binary_tree/segment_tree_other.py b/data_structures/binary_tree/segment_tree_other.py
index 93b603cdc..c3ab493d5 100644
--- a/data_structures/binary_tree/segment_tree_other.py
+++ b/data_structures/binary_tree/segment_tree_other.py
@@ -18,7 +18,7 @@ class SegmentTreeNode(object):
         self.right = right
 
     def __str__(self):
-        return 'val: %s, start: %s, end: %s' % (self.val, self.start, self.end)
+        return "val: %s, start: %s, end: %s" % (self.val, self.start, self.end)
 
 
 class SegmentTree(object):
@@ -131,6 +131,7 @@ class SegmentTree(object):
     >>>
 
     """
+
     def __init__(self, collection: Sequence, function):
         self.collection = collection
         self.fn = function
@@ -197,7 +198,10 @@ class SegmentTree(object):
                 return self._query_range(node.left, i, j)
             else:
                 # range in left child tree and right child tree
-                return self.fn(self._query_range(node.left, i, node.mid), self._query_range(node.right, node.mid + 1, j))
+                return self.fn(
+                    self._query_range(node.left, i, node.mid),
+                    self._query_range(node.right, node.mid + 1, j),
+                )
         else:
             # range in right child tree
             return self._query_range(node.right, i, j)
@@ -217,10 +221,11 @@ class SegmentTree(object):
                     queue.put(node.right)
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     import operator
+
     for fn in [operator.add, max, min]:
-        print('*' * 50)
+        print("*" * 50)
         arr = SegmentTree([2, 1, 5, 3, 4], fn)
         for node in arr.traverse():
             print(node)
diff --git a/data_structures/stacks/stack.py b/data_structures/stacks/stack.py
index a96275aa8..baa0857ee 100644
--- a/data_structures/stacks/stack.py
+++ b/data_structures/stacks/stack.py
@@ -46,11 +46,11 @@ class Stack:
     def size(self):
         """ Return the size of the stack."""
         return len(self.stack)
-    
+
     def __contains__(self, item) -> bool:
         """Check if item is in stack"""
         return item in self.stack
-    
+
 
 class StackOverflowError(BaseException):
     pass
@@ -73,4 +73,3 @@ if __name__ == "__main__":
     num = 5
     if num in stack:
         print(f"{num} is in stack")
-