added dijkstras algorithm [Python]

Python/Dijkstras.py

@@ -0,0 +1,50 @@
+
+import math
+
+def Dijkstras(graph, start, goal):
+    unseenNodes = graph
+    predecessor = {}
+    shortest_distance = {}
+    path = []
+    infinty = math.inf
+
+    for node in unseenNodes:
+        shortest_distance[node] = infinty
+    shortest_distance[start] = 0
+
+    while unseenNodes:
+        minNode = None
+        for node in unseenNodes:
+            if minNode is None:
+                minNode = node
+
+            elif shortest_distance[node] < shortest_distance[minNode]:
+                minNode = node
+
+        for chilNode,weight in graph[minNode].items():
+            if weight + shortest_distance[minNode] < shortest_distance[chilNode]:
+                shortest_distance[chilNode] = weight + shortest_distance[minNode]
+                predecessor[chilNode] = minNode
+
+        unseenNodes.pop(minNode)
+
+
+    currenNode = goal
+    while currenNode != start:
+        try:
+            path.insert(0,currenNode)
+
+            currenNode = predecessor[currenNode]
+        except KeyError:
+            print('path not found')
+            break
+
+    path.insert(0,start)
+
+    if shortest_distance[goal] != infinty:
+        print('The shortest distance is ' + str(shortest_distance[goal]))
+        print('And the path is ' + str(path))
+
+
+graph = {'a':{'b':10,'c':3},'b':{'c':1,'d':2},'c':{'b':4,'d':8,'e':2},'d':{'e':7},'e':{'d':9}}
+Dijkstras(graph, 'a', 'd')