ch02

ch02/defaultdict.py

@@ -0,0 +1,18 @@
+# defaultdict.py
+
+
+>>> d = {}
+>>> d['age'] = d.get('age', 0) + 1  # age not there, we get 0 + 1
+>>> d
+{'age': 1}
+>>> d = {'age': 39}
+>>> d['age'] = d.get('age', 0) + 1  # age is there, we get 40
+>>> d
+{'age': 40}
+
+
+>>> from collections import defaultdict
+>>> dd = defaultdict(int)  # int is the default type (0 the value)
+>>> dd['age'] += 1  # short for dd['age'] = dd['age'] + 1
+>>> dd
+defaultdict(<class 'int'>, {'age': 1})  # 1, as expected