python3输出重复数据的方法

data={
    "1001":"apple",
    "1002":"pear",
    "1003":"peach",
    "1004":"banana",
    "1005":"apple",
"1006":"peach"}

from collections import Counter
counter = Counter(a.values())
for item in counter:
    if counter[item] > 1:
        print(item)

d = {}
for line in open('a.txt'):
    d[line] = d.get(line, 0) + 1 
fd = open('b.txt', 'w')
for k, v in d.items():
    if v > 1: 
        fd.write(k)
fd.close()