added comments to code

Author: Xceptions

BrowserHistory/backend.py

@@ -1,4 +1,9 @@
 class DLL:
+    """
+        a doubly linked list that holds the current page,
+        next page, and previous page.
+        Used to enforce order in operations
+    """
     def __init__(self, val: str =None):
         self.val = val
         self.nxt = None
@@ -7,15 +12,30 @@ def __init__(self, val: str =None):
 
 class BrowserHistory:
     """
-        This class designs the operations of a
-        broswer history
+    This class designs the operations of a browser history
+
+    It works by using a doubly linked list to hold the urls
     """
 
     def __init__(self, homepage: str):
+        """
+        Returns - None
+        Input - None
+        ----------
+        - Initialize doubly linked list which will serve as the
+            browser history and sets the current page
+        """
         self.head = DLL(homepage)
         self.curr = self.head
 
     def visit(self, url: str) -> None:
+        """
+        Returns - None
+        Input - str
+        ----------
+        - Adds the current url to the DLL
+        - sets both the next and previous values
+        """
         url_node = DLL(url)
         self.curr.nxt = url_node
         url_node.prev = self.curr
@@ -24,13 +44,27 @@ def visit(self, url: str) -> None:
 
 
     def back(self, steps: int) -> str:
+        """
+        Returns - str
+        Input - int
+        ----------
+        - Iterates through the DLL backwards `step` number of times
+        - returns the appropriate value
+        """
         while steps > 0 and self.curr.prev:
             self.curr = self.curr.prev
             steps -= 1
         return self.curr.val
 
 
     def forward(self, steps: int) -> str:
+        """
+        Returns - str
+        Input - int
+        ----------
+        - Iterates through the DLL forewards `step` number of times
+        - returns the appropriate value
+        """
         while steps > 0 and self.curr.nxt:
             self.curr = self.curr.nxt
             steps -= 1