learning dict

Author: greyshell

ds_algorithm/README.md ds_algo/README.mdds_algorithm/README.md renamed to ds_algo/README.md

@@ -0,0 +1,43 @@
+# !/usr/bin/env python3
+
+# author: greyshell
+# description: play with dict
+
+
+def main():
+    """
+    - TBD
+    :return:
+    """
+    # create a empty dict
+    a = {}
+    d = dict()
+
+    # initialise
+    name_dept = {
+        "alice": "cse",
+        "bob": "ee",
+        "carol": "it"
+    }
+
+    # look up: method 1
+    try:
+        dept = name_dept["no_key"]  # throws exception when the key is not found
+        print(f"{dept}")
+    except KeyError as e:
+        print(f"error: {e}")
+
+    # look up: method 2
+    if "no_key" in name_dept:  # inefficient because it queries the dict twice
+        dept = name_dept["no_key"]
+        print(f"{dept}")
+
+    # look up: method 3 (recommended)
+    dept = name_dept.get("alice", "no_key")  # provides the support for default value
+    print(f"{dept}")
+
+    # add items
+
+
+if __name__ == '__main__':
+    main()

ds_algo/dict/test/test_dict.py

@@ -9,8 +9,8 @@ def main():
     - python list is backed by dynamic array, so occasionally it needs to be resized when item is added / removed
     - it does not guarantee the stable O(1) push and pop
     - however, it provides the amortize time complexity is O(1) when the item is added / remove at the end of list
-    - adding / removing from front is much slower and it takes O(n) time as shifting of existing elements are required
-    - IndexError => pop from an empty list
+    - adding / removing from front / middle is much slower and it takes O(n) time as shifting of existing elements
+    are required
     - no parallel processing support / it handles locking and unlocking
     :return:
     """
@@ -29,8 +29,12 @@ def main():
     print(f"peek the stack top: {data}")
 
     # pop: O(1), stack shrinks from right to left
-    data = s.pop()
-    print(f"popped: {data}")
+    # raise IndexError => pop from an empty list
+    try:
+        data = s.pop()
+        print(f"popped: {data}")
+    except IndexError as e:
+        print(f"{e}")
 
     print(f"display the stack elements: {list(s)}")
 

ds_algorithm/graph/dijkstra.py ds_algo/graph/dijkstra.pyds_algorithm/graph/dijkstra.py renamed to ds_algo/graph/dijkstra.py

@@ -10,7 +10,6 @@ def main():
     """
     - deque is backed by doubly linked list
     - it that guarantees the stable O(1) push and pop
-    - IndexError => pop from an empty list
     - no parallel processing support / it handles locking and unlocking
     :return:
     """
@@ -30,8 +29,12 @@ def main():
     print(f"peek the stack top: {data}")
 
     # pop: O(1), stack shrinks from right to left
-    data = s.pop()
-    print(f"popped: {data}")
+    # raise IndexError => pop from an empty list
+    try:
+        data = s.pop()
+        print(f"popped: {data}")
+    except IndexError as e:
+        print(f"{e}")
 
     print(f"display the stack elements: {list(s)}")
 

ds_algorithm/heap/continuous_median.py ds_algo/heap/continuous_median.pyds_algorithm/heap/continuous_median.py renamed to ds_algo/heap/continuous_median.py

@@ -23,8 +23,16 @@ def main():
     # not found any method for peek and display stack elements
 
     # pop: O(1)
-    data = s.get_nowait()  # not wait for producer to add the element if the stack is empty
-    print(f"popped: {data}")
+    data = s.get_nowait()
+    data = s.get_nowait()
+
+    try:
+        data = s.get_nowait()  # not wait for producer to add the element if the stack is empty
+        print(f"popped: {data}")
+    except Exception as e:
+        print(f"{e}")
+
+    exit(0)
 
     data = s.get()  # poped out the last stack element
     data = s.get()  # waits for ever as the stack is empty, producer needs to add an element