Functional Programming HowTo, near the end, has a section Small functions and the lambda expression http://docs.python.org/3/howto/functional.html#small-functions-and-the-lambda-expression To illustrate, it starts with adder = lambda x, y: x+y print_assign = lambda name, value: name + '=' + str(value) which are now proscribed by PEP 8. "Always use a def statement instead of an assignment statement that binds a lambda expression directly to a name." The text goes on to give the def equivalents and to discourage lambdas. "Which alternative is preferable? That’s a style question; my usual course is to avoid using lambda." But I think the section should instead start with lambda examples that would be acceptable in the stdlib.
I would just change "my usual course is to avoid using lambda" to "PEP 8 prescribes using def." Note that PEP 8 itself displays f = lambda x: 2*x as an example of what not to do. I see no problem with the current examples.
IMHO that part should not suggest to use lambdas as small functions, so I would drop the example with adder/print_assign and the discussion about lambdas vs defs (the example that uses defs can stay), and keep the rest (from the "reduce" example).
