python 数据类型

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删除列表中重复元素，并保持顺序不变
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def dedupe(items):
    ‘‘‘
    对对可哈希类型排序
    :param items:
    :return:
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    seen=set()
    for item in items:
        if item not in seen:
            yield item
            seen.add(item)

def buha(items,key=None):
    ‘‘‘
    对所有类型排序
    :param items:
    :param key:
    :return:
    ‘‘‘
    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)
if __name__ == ‘__main__‘:
    a=[5,5,2,1,6,7,3]
    print(a)
    print(list(dedupe(a)))

    b=[{‘x‘:2,‘y‘:3},{‘x‘:3,‘y‘:3},{‘x‘:6,‘y‘:4},{‘x‘:2,‘y‘:3},{‘x‘:5,‘y‘:5},{‘x‘:5,‘y‘:3},{‘x‘:5,‘y‘:3},]
    key=lambda b:(b[‘x‘],b[‘y‘])
    print(list(buha(b,key)))

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找出列表中出现次数最多的元素

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from collections import Counter
words=[1,2,33,45,657,4,56,33,22,66,33,22,22]
words_count=Counter(words)
#输出出现次数最多的前三
top_three=words_count.most_common(3)
print(words_count)
print(top_three)

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创建包含1到10平方的列表
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squares=[]
for x in range(1,11):
    squares.append(x**2)
print(squares)
#
squares2=[x**2 for x in range(1,11)]
print(squares2)

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获取0到30，能被3整除的数平方的列表
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sq=[i**2 for i in range(1,31) if i%3 is 0]
print(sq)

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切片
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items=[0,1,2,3,4,5,6]
#切片
print(items[2:4])
#取出所有
print(items[0:-1])
#通过slice切片
a=slice(2,4)
print(items[a])
#倒序
print(items[-1:0:-1])

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获取列表中所有数字
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values=[‘1‘,‘2‘,‘3‘,‘4‘,‘-5‘,‘-‘,‘t‘]

def is_int(val):
    try:
        x=int(val)
        return True
    except ValueError:
        return False
#过滤并存到列表
ivals=list(filter(is_int,values))
print(ivals)