iterating_through_submasks is added with doctests

Author: faizan2700

dynamic_programming/iterating_through_submasks.py

@@ -1,10 +1,13 @@
-'''
+"""
+Author : Syed Faizan (3rd Year Student IIIT Pune) 
+github : faizan2700
 You are given a bitmask m and you want to efficiently iterate through all of
 its submasks. The mask s is submask of m if only bits that were included in
 bitmask are set
-'''
+"""
 
-def list_of_submasks(mask)->list:
+
+def list_of_submasks(mask) -> list:
 
     """
     Args:
@@ -21,26 +24,36 @@ def list_of_submasks(mask)->list:
     [15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
     >>> list_of_submasks(13)
     [13, 12, 9, 8, 5, 4, 1]
+    >>> list_of_submasks(-7)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+        ...
+    AssertionError: mask needs to be positive integer, your input -7
+    >>> list_of_submasks(0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+        ...
+    AssertionError: mask needs to be positive integer, your input 0
     
     """
 
     fmt = "n needs to be positive integer, your input {}"
     assert isinstance(mask, int) and mask > 0, fmt.format(mask)
-    
-    '''
+
+    """
     first submask iterated will be mask itself then operation will be performed
     to get other submasks till we reach empty submask that is zero ( zero is not
     included in final submasks list )
-    '''
+    """
     all_submasks = []
     submask = mask
 
     while submask:
         all_submasks.append(submask)
-        submask = (submask-1) & mask
-    
+        submask = (submask - 1) & mask
+
     return all_submasks
 
-if __name__ == '__main__':
+
+if __name__ == "__main__":
     import doctest
+
     doctest.testmod()