以下是一个示例代码，演示如何按照特定键计算字典中的重复项：

def count_duplicates(dictionary, key):
    count = {}
    for item in dictionary:
        if dictionary[item][key] in count:
            count[dictionary[item][key]] += 1
        else:
            count[dictionary[item][key]] = 1
    return count

# 示例字典
my_dict = {
    'item1': {'key1': 'value1', 'key2': 'value2'},
    'item2': {'key1': 'value3', 'key2': 'value4'},
    'item3': {'key1': 'value1', 'key2': 'value5'},
    'item4': {'key1': 'value3', 'key2': 'value6'},
    'item5': {'key1': 'value1', 'key2': 'value7'}
}

# 按照 key1 计算重复项
duplicates = count_duplicates(my_dict, 'key1')

# 输出结果
for key, value in duplicates.items():
    print(f"键 {key} 有 {value} 个重复项")

输出结果将会是：

键 value1 有 3 个重复项
键 value3 有 2 个重复项