Python序列删除重复数据

## 对于列表来说，若不保持原有顺序，可以直接转换为set删除重复数据

 nums = [1,2,32,2,2,4,3,2,3,42]
 nums = list(set(nums))
 print(nums)
 # [32, 1, 2, 3, 4, 42]  # 删除了重复数据，但是原有顺序也改变了

## 删除数据并保持原有顺序

 def dedupe(items, key=None):
     """
     items: 哈希或者不可哈希的序列
     key: 若items为不可哈希的序列(dict等)则需要指定一个函数
     """
     seen = set()
     for item in items:
         val = item if key is None else key(item)
         if val not in seen:
             yield item
             seen.add(val)

 nums = [1,2,32,2,2,4,3,2,3,42]
 print(list(dedupe(nums)))
 # [1, 2, 32, 4, 3, 42]

 students = [
     {"name": "Stanley", "score": 88},
     {"name": "Lily", "score": 92},
     {"name": "Bob", "score": 91},
     {"name": "Well", "score": 80},
     {"name": "Bob", "score": 90},
     {"name": "Peter", "score": 80}
 ]
 deduped_students = list(dedupe(students, key=lambda s: s['name']))
 print(deduped_students)
 """
 [{'name': 'Stanley', 'score': 88},
 {'name': 'Lily', 'score': 92},
 {'name': 'Bob', 'score': 91},
 {'name': 'Well', 'score': 80},
 {'name': 'Peter', 'score': 80}]   # 删除了相同姓名的元素
 """
 # 删除姓名和分数都相同的元素
 deduped_students = list(dedupe(students, key=lambda s: (s['name'], s['score'])))

参考资料：
　　Python Cookbook, 3rd edition, by David Beazley and Brian K. Jones (O’Reilly).