On Wed, Aug 17, 2016 at 10:14 PM, Shiyao Ma <i...@introo.me> wrote: > Hi, > > I am using Python2. > > For the following snippet, > > http://ideone.com/i36pKO > > I'd suppose the dummy_func would be invoked, but seems not. > > Indeed, heapq.heapify does invoke cmp_lt per here: > https://hg.python.org/cpython/file/2.7/Lib/heapq.py#l136 > > So why this way of monkey patching failed?
Because of this: https://hg.python.org/cpython/file/2.7/Lib/heapq.py#l351 When you call heapq.heapify, it's not actually calling the reference implementation in that file. It's actually calling a C implementation that totally ignores everything in that module. If you really want to do this, you can disable the C implementation by adding this before importing heapq: import sys sys.modules['_heapq'] = None This marks the _heapq module as not found in the module cache, which prevents he module loader from trying to import it, resulting in heapq using the reference implementation instead. I don't recommend doing this, however. You'd be disabling the more efficient implementation in order to monkey-patch an undocumented function that should be considered an implementation detail. For example, that cmp_lt function doesn't even exist in Python 3: https://hg.python.org/cpython/file/tip/Lib/heapq.py -- https://mail.python.org/mailman/listinfo/python-list
