obj: reify for python

gistfile1.py

# Writing some unit tests in Python, I found myself homesick for Clojure's `reify`.

from functools import partial

class Blank(object): pass

def obj(*fs):
    o = Blank()
    for f in fs:
        setattr(o, f.func_name, partial(f, o))
    return o
    
#Use it like this:

from nose.tools import eq_
import json

def cut_suffix_strict(s, suffix):
    ok_(s.endswith(suffix), '%s does not end with %s' % (s, suffix))
    return s[:-len(suffix)]

def fake_conn(bucket_name, folder_name, mappings):
    def get_bucket(self, passed_bucket_name):
        eq_(bucket_name, passed_bucket_name)
        def get_key(self, path):
            passed_folder, full_key = path.split('/')
            eq_(passed_folder, folder_name)
            key = cut_suffix_strict(full_key, '.json')
            def get_contents_as_string(self):
                return json.dumps(mappings[key])
            return obj(get_contents_as_string)
        return obj(get_key)
    return obj(get_bucket)

# Calling fake_conn() gets you an object mocking boto's S3Connection class.
# You can call get_bucket() on it to get a fake bucket, call get_key() on that to get a fake key, etc.
# Unlike reify, you don't pass in an interface/protocol -- none of those in Python.
# Like reify, your functions should take a self param.