organization in the src structure, modification of README

src/builtin_structures/dicts/Counter_example.py

@@ -0,0 +1,33 @@
+#!/usr/bin/python3
+# mari von steinkirch @2013
+# steinkirch at gmail
+
+from collections import Counter
+
+def  Counter_example():
+    ''' show some examples for Counter ''' 
+    ''' it is a dictionary that maps the items to the number of occurences '''
+    seq1 = [1, 2, 3, 5, 1, 2, 5, 5, 2, 5, 1, 4]
+    seq_counts = Counter(seq1)
+    print(seq_counts)
+    
+    ''' we can increment manually or use the update() method '''
+    seq2 = [1, 2, 3]
+    seq_counts.update(seq2)
+    print(seq_counts)
+    
+    seq3 = [1, 4, 3]
+    for key in seq3:
+        seq_counts[key] += 1
+    print(seq_counts)
+        
+    ''' also, we can use set operations such as a-b or a+b '''
+    seq_counts_2 = Counter(seq3)
+    print(seq_counts_2)  
+    print(seq_counts + seq_counts_2)  
+    print(seq_counts - seq_counts_2)
+    
+if __name__ == '__main__':
+    Counter_example()
+
+