Added source code for 'Swap nodes in pairs' problem in Python

Recursion/python/Swap_Nodes_In_Pairs.py

@@ -0,0 +1,17 @@
+# Given a linked list, swap every two adjacent nodes and return its head.
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+
+def swapPairs(head):
+    # Base condition for recursive solution
+    if head is not None:
+        if head.next is None:
+            return head
+        # next element of head will be swapped head
+        new_head = head.next
+        # Swapping algorithm: recursion
+        new_head.next, head.next = head, swapPairs(new_head.next)
+        return new_head