PEP 572: Change toy example to not be a simple pair

pep-0572.rst

@@ -52,26 +52,29 @@ Example usage
 These list comprehensions are all approximately equivalent::
 
     # Calling the function twice
-    stuff = [[f(x), f(x)] for x in range(5)]
+    stuff = [[f(x), x/f(x)] for x in range(5)]
 
     # External helper function
-    def pair(value): return [value, value]
+    def pair(value): return [value, x/value]
     stuff = [pair(f(x)) for x in range(5)]
 
     # Inline helper function
-    stuff = [(lambda y: [y,y])(f(x)) for x in range(5)]
+    stuff = [(lambda y: [y,x/y])(f(x)) for x in range(5)]
 
     # Extra 'for' loop - see also Serhiy's optimization
-    stuff = [[y, y] for x in range(5) for y in [f(x)]]
+    stuff = [[y, x/y] for x in range(5) for y in [f(x)]]
+
+    # Iterating over a genexp (similar to the above but reordered)
+    stuff = [[y, x/y] for y in (f(x) for x in range(5))]
 
     # Expanding the comprehension into a loop
     stuff = []
     for x in range(5):
         y = f(x)
-        stuff.append([y, y])
+        stuff.append([y, x/y])
 
     # Using a statement-local name
-    stuff = [[(f(x) as y), y] for x in range(5)]
+    stuff = [[(f(x) as y), x/y] for x in range(5)]
 
 If calling ``f(x)`` is expensive or has side effects, the clean operation of
 the list comprehension gets muddled. Using a short-duration name binding