Mongo Query Ops

def both(a,b):
	return equals('$and', [a,b])

def exists(fieldname):
	d = {}
	d[str(fieldname)] = {'$exists': True }
	return d

def equals(fieldname, value):
	d = {}
	d[str(fieldname)] = value
	return d

# 'in' is a python keyword
def contains(fieldname, array):
	d = {}
	d[str(fieldname)] = {'$in': array}
	return d

def not_in(fieldname, array):
	d = {}
	d[str(fieldname)] = {'$nin': array}
	return d

def combine(*docs):
	d = {}
	for doc in docs: 
		d.update(doc)
	return d

def update(fieldname, value):
	return { '$set': { str(fieldname): value}}

def _get(fieldname):
	return { str(fieldname): True }

def by(key):
	return equals(ID, key)

class Is(object):
	def __init__(self, value):
		self.value = value
	def __getattr__(self, name):
		return equals(name, self.value)

true = Is(True)
false = Is(False)

class Get(object):
	def __call__(self, fieldname):
		return _get(fieldname)
	def __getattr__(self, fieldname):
		return _get(fieldname)
	
get = Get()

ID = '_id'
pk = get(ID)