class Field(object):

	def __init__(self, fid, sid, name, unit):
		self.fid = fid
		self.sid = sid
		self.name = name
		self.unit = unit

	@staticmethod
	def get_by_fid(fid):
		with sqlite3.connect("db.sqlite") as conn:
			results = conn.execute("SELECT * FROM fields WHERE fid=?;",[fid])
			result = results[0]
			return Field(result[0], result[1], result[2], result[3])

	@staticmethod
	def get_by_name(sid, name):
		with sqlite3.connect("db.sqlite") as conn:
			results = conn.execute("SELECT * FROM fields WHERE sid=? AND name=?;",[sid,name])
			result = results[0]
			return Field(result[0], result[1], result[2], result[3])

my_field = Field.get_by_fid(123)
print("Field name is: {}".format(my_field.name))