There is a bug in #1. The condition should be `i % 2 == 0` to get even numbers: def halves_of_evens(nums): for i in nums: div, mod = divmod(i

There is a bug in #1. The condition should be `i % 2 == 0` to get even numbers: def halves_of_evens(nums): for i in nums: div, mod = divmod(i, 2) #NOTE: it might be slower if mod == 0: #NOTE: `not mod` is not explicit enough yield div #2: Function level import is a bad practice though it might be justified in this case. #3: `users` is not defined. `sqlalchemy` names are not defined. The file should be opened for writing in the json example. #5 It is simpler to allow the animal to know its kind: def identify(animal): return animal.__class__.__name__ or just: animal.kind #6 `elem.xpath('./a/@href')` is simpler than [a.attrib[’href’] for a in elem.find(’./a’) if ’href’ in a.attrib] Also `elem.iterlinks()` could be used http://codespeak.net/lxml/lxmlhtml.html#working-with-links http://codespeak.net/lxml/lxmlhtml.html#working-with-links There is no `lxml.CSSSelector` (python-lxml 2.2.6-1). Use `elem.cssselect` #7 You don't need to add `ifmain` stub in every module: $ python -mdoctest module_with_doctests.py $ python -munittest module_with_unittests.py # 8 & 9: The first variant of `make_counter()` won't work without `nonlocal i` -- it leads to `UnboundLocalError` otherwise. Despite the fact that it works on my machine on all available Python implementations such code should be avoided: assert float(’0.20000000000000007’) == 1.1 - 0.9 #XXX horror! # 10 & 11: Use stdlib's version: try: import json except ImportError: import simplejson as json It is a matter of preference but it makes testing more predictable. #13 `__builtins__` is not defined on jython: try: import __builtin__ as builtins except ImportError: import builtins # py3k