Initial commit of item_05

Author: craigem

item_05.py

@@ -0,0 +1,98 @@
+#!/usr/bin/env python3
+
+'''Item 5 from Effective Python'''
+
+import logging
+from pprint import pprint
+from sys import stdout as STDOUT
+
+
+# Example 1
+print('Example 1:\n==========')
+a = [
+        'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
+        'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'
+    ]
+print('First four:', a[:4])
+print('Last four: ', a[-4:])
+print('Middle two:', a[3:-3])
+
+
+# Example 2
+assert a[:5] == a[0:5]
+
+
+# Example 3
+assert a[5:] == a[5:len(a)]
+
+
+# Example 4
+print('\nExample 4:\n==========')
+print(a[:5])
+print(a[:-1])
+print(a[4:])
+print(a[-3:])
+print(a[2:5])
+print(a[2:-1])
+print(a[-3:-1])
+
+
+# Example 5
+a[:]      # ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']
+a[:5]     # ['a', 'b', 'c', 'd', 'e']
+a[:-1]    # ['a', 'b', 'c', 'd', 'e', 'f', 'g']
+a[4:]     #                     ['e', 'f', 'g', 'h']
+a[-3:]    #                          ['f', 'g', 'h']
+a[2:5]    #           ['c', 'd', 'e']
+a[2:-1]   #           ['c', 'd', 'e', 'f', 'g']
+a[-3:-1]  #                          ['f', 'g']
+
+
+# Example 6
+print('\nExample 6:\n==========')
+first_twenty_items = a[:20]
+last_twenty_items= a[-20:]
+print('First twenty items: %s' % first_twenty_items)
+print('Last twenty items:  %s' % last_twenty_items)
+
+
+# Example 7
+print('\nExample 7:\n==========')
+try:
+    a[20]
+except:
+    logging.exception('Expected')
+else:
+    print('a[20] is: %s' % a[20])
+
+
+# Example 8
+print('\nExample 8:\n==========')
+b = a[4:]
+print('Before:    ', b)
+b[1] = 99
+print('After:     ', b)
+print('No change: ', a)
+
+
+# Example 9
+print('\nExample 9:\n==========')
+print('Before ', a)
+a[2:7] = [99, 22, 14]
+print('After ', a)
+
+
+# Example 10
+print('\nExample 10:\n==========')
+b = a[:]
+assert b == a and b is not a
+print(b)
+
+
+# Example 11
+print('\nExample 11:\n==========')
+b = a
+print('Before', a)
+a[:] = [101, 102, 103]
+assert a is b           # Still the same list object
+print('After ', a)      # Now has different contents