ch02

ch02/final_considerations.py

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+# final_considerations.py
+
+
+>>> a = 1000000
+>>> b = 1000000
+>>> id(a) == id(b)
+False
+
+
+>>> a = 5
+>>> b = 5
+>>> id(a) == id(b)
+True
+
+
+# how to choose data structures
+# example customer objects
+customer1 = {'id': 'abc123', 'full_name': 'Master Yoda'}
+customer2 = {'id': 'def456', 'full_name': 'Obi-Wan Kenobi'}
+customer3 = {'id': 'ghi789', 'full_name': 'Anakin Skywalker'}
+# collect them in a tuple
+customers = (customer1, customer2, customer3)
+# or collect them in a list
+customers = [customer1, customer2, customer3]
+# or maybe within a dictionary, they have a unique id after all
+customers = {
+    'abc123': customer1,
+    'def456': customer2,
+    'ghi789': customer3,
+}
+
+
+# negative indexing
+>>> a = list(range(10))  # `a` has 10 elements. Last one is 9.
+>>> a
+[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+>>> len(a)  # its length is 10 elements
+10
+>>> a[len(a) - 1]  # position of last one is len(a) - 1
+9
+>>> a[-1]  # but we don't need len(a)! Python rocks!
+9
+>>> a[-2]  # equivalent to len(a) - 2
+8
+>>> a[-3]  # equivalent to len(a) - 3
+7