python 基础——常用功能片段

1. 元素去重

data = [1,2,3,4,4,5,5,6]
res = set(data)

2. 元素去重排序

res = sorted(set(data))

2. 打印重复的元素

res = [x for x in data if data.count(x) > 1]

3. 阶乘

num = 10
res = reduce(lambda x, y: x*y, range(num+1)[1:])

6. 列表推导式

origin = ['a', 'b', 'c', 'z']

print [x for x in origin if x is not 'z']    # ['a', 'b', 'c']
print [x for x in list(enumerate(origin, 5)) if x is not 'z']    # [(5, 'a'), (6, 'b'), (7, 'c'), (8, 'z')]

7. 字典推导式

origin = ['a', 'b', 'c', 'z']

res = {x: origin.index(x) for x in origin}    # {'a': 0, 'c': 2, 'b': 1, 'z': 3}
print type(res)    # <type 'dict'>

8. 集合推导式

origin = ['a', 'b', 'c', 'z']

print {x*2 for x in origin}    # set(['aa', 'cc', 'zz', 'bb'])

9. 生成器推导式(有点像元组)

origin = ['a', 'b', 'c', 'z']

res = (x*2 for x in origin)
print res    # <generator object <genexpr> at 0x7fe2ca76d640>
print type(res)    # <type 'generator'>

10.生成器和其它集合的转换

def test():
    for i in [1, 2,3]:
        yield i

res = test()
print res    # <generator object test at 0x7f404d077640>
res1 = set(res)
print res1    # set([1, 2, 3])
res2 = list(res)
print res2    #为空 生成器是有状态的，不能反复调用
res3 = tuple(res)
print res3    #为空 生成器是有状态的，不能反复调用