gistfile1.txt

	data = {}
	with open("C:/Python27/pythoncbr/data/"+filename,"rb") as f:
		reader = csv.DictReader(f)
		for row in reader:
			if row['Customer ID'] != "":
				key = row['Customer ID']
				data.setdefault(key, [])
				data[key].append(row['prodID'])
			if row['Customer ID'] == "":
				data[key].append(row['prodID'])
	return data
Data in excel is like this 
Cust id, prod id, amount, stockist type
c1        p1      100     large
          p2      200