how generate complex AND query using Q() in django

how generate complex AND query using Q() in django

queries = request.POST.get('query', '')
print "quires -->", queries
if queries:
queries = json.loads(queries)
print "json queries -->", queries
q = Q()
for field, condition, query in queries:
print "field -->", field
print "condition -->", condition
print "query -->", query
q = q & Q(**{str(field)+"__"+str(condition):query})
print "query output -->", q
book = Book.objects.filter(q & Q(library=library_id)).order_by(*s)

output:
-------
quires --> [["author","icontains","saju"],["editor","startswith","a"]]
json queries --> [[u'author', u'icontains', u'saju'], [u'editor', u'startswith', u'a']]

field -->author
condition-->icontains
query -->saju

field -->editor
condition-->startswith
query -->a

query output --> (AND: ('author__icontains', u'saju'), ('editor__startswith', u'a'))

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** --> Means keyword argument
* --> Means positional argument

Q() --> can accept keyword argument
order_by() --> can accept positional argument

Q(**{str(field)+"__"+str(condition):query})
order_by(*s)

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for field, condition, query in queries:
Q(**{str(field)+"__"+str(condition):query})

is equivalent to

Q(**{'author__icontains':'saju', 'editor__startswith':'a'})

that is Q() with keyword arguments

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