from datetime import datetime, timedelta
from sqlalchemy import and_
thirty_days_ago = datetime.today() - timedelta(days = 30)
fifteen_days_ago = datetime.today() - timedelta(days = 15)
# Using and_ IMPLICITLY:
payments = Payment.query.filter(Payment.due_date >= thirty_days_ago,
Payment.due_date <= fifteen_days_ago).all()
# Using and_ explicitly:
payments = Payment.query.filter(and_(Payment.due_date >= thirty_days_ago,
Payment.due_date <= fifteen_days_ago)).all()