initial commit of item_04

Author: craigem

Diff for: item_04.py

@@ -0,0 +1,98 @@
+#!/usr/bin/env python3
+
+'''Item 4 from Effective Python'''
+
+
+# Example 1
+from urllib.parse import parse_qs
+MY_VALUES = parse_qs('red=5&blue=0&green=', keep_blank_values=True)
+print('Example 1:\n==========')
+print(repr(MY_VALUES))
+
+
+# Example 2
+print('\nExample 2:\n==========')
+print('Red:     ', MY_VALUES.get('red'))
+print('Green:   ', MY_VALUES.get('green'))
+print('Opacity: ', MY_VALUES.get('opactity'))
+
+
+# Example 3
+# For query string 'red=5&blue=0&green='
+RED = MY_VALUES.get('red', [''])[0] or 0
+GREEN = MY_VALUES.get('green', [''])[0] or 0
+OPACITY = MY_VALUES.get('opacity', [''])[0] or 0
+print('\nExample 3:\n==========')
+print('Red:     %r' % RED)
+print('Green:   %r' % GREEN)
+print('Opacity: %r' % OPACITY)
+
+
+# Example 4
+RED = int(MY_VALUES.get('red', [''])[0] or 0)
+GREEN = int(MY_VALUES.get('green', [''])[0] or 0)
+OPACITY = int(MY_VALUES.get('opacity', [''])[0] or 0)
+print('\nExample 4:\n==========')
+print('Red:     %r' % RED)
+print('Green:   %r' % GREEN)
+print('Opacity: %r' % OPACITY)
+
+
+# Example 5
+RED = MY_VALUES.get('red', [''])
+RED = int(RED[0]) if RED[0] else 0
+GREEN = MY_VALUES.get('green', [''])
+GREEN = int(GREEN[0]) if GREEN[0] else 0
+OPACITY = MY_VALUES.get('opacity', [''])
+OPACITY = int(OPACITY[0]) if OPACITY[0] else 0
+print('\nExample 5:\n==========')
+print('Red:     %r' % RED)
+print('Green:   %r' % GREEN)
+print('Opacity: %r' % OPACITY)
+
+
+# Example 6
+RED = MY_VALUES.get('red', [''])
+if RED[0]:
+    RED = int(RED[0])
+else:
+    RED = 0
+
+GREEN = MY_VALUES.get('green', [''])
+if GREEN[0]:
+    GREEN = int(GREEN[0])
+else:
+    GREEN = 0
+
+OPACITY = MY_VALUES.get('opacity', [''])
+if OPACITY[0]:
+    OPACITY = int(OPACITY[0])
+else:
+    OPACITY = 0
+
+print('\nExample 6:\n==========')
+print('Red:     %r' % RED)
+print('Green:   %r' % GREEN)
+print('Opacity: %r' % OPACITY)
+
+
+# Example 7
+def get_first_int(values, key, default=0):
+    '''Writing a helper function is the way to go, especially if you need to
+    use this logic repeatedly.'''
+    found = values.get(key, [''])
+    if found[0]:
+        found = int(found[0])
+    else:
+        found = default
+    return found
+
+
+# Example 8
+RED = get_first_int(MY_VALUES, 'red')
+GREEN = get_first_int(MY_VALUES, 'green')
+OPACITY = get_first_int(MY_VALUES, 'opacity')
+print('\nExample 8:\n==========')
+print('Red:     %r' % RED)
+print('Green:   %r' % GREEN)
+print('Opacity: %r' % OPACITY)