if we must argue over the/they, we can just remove the unecessary word

Doc/tut/tut.tex

@@ -4405,7 +4405,7 @@ Some simple generators can be coded succinctly as expressions using a syntax
 similar to list comprehensions but with parentheses instead of brackets.  These
 expressions are designed for situations where the generator is used right
 away by an enclosing function.  Generator expressions are more compact but
-less versatile than full generator definitions and they tend to be more memory
+less versatile than full generator definitions and tend to be more memory
 friendly than equivalent list comprehensions.
 
 Examples: