Question

我正在尝试解决一个练习，我必须转换这个

L = ([[4,1],[2,2],[2,"test"],[3,3],[1,"bonjour"]])
decompress (L)

进入这个

[1,1,1,1,2,2,"test","test",3,3,3,"bonjour"]

这就是我开始的方式：

def por(L):
    result = []
    n = len(L)
    for i in range(n):
        m = len(L[i])
        for j in range(m):
            mult = L[j]*L[j-1]
            result.append(mult)
    return result

por([[4,1],[2,2],[2,"test"],[3,3],[1,"bonjour"]])

Traceback (most recent call last):
File "<pyshell#50>", line 1, in <module>
por([[4,1],[2,2],[2,"test"],[3,3],[1,"bonjour"]])
File "<pyshell#49>", line 7, in por
mult = L[j]*L[j-1]
TypeError: can't multiply sequence by non-int of type 'list'

我没有弄错，有人可以帮助我，这是我的考试!!!!

Answer 1

def por(L):
    # add each sublist element 1  sublist element 0 times
    return [sub_list[1]  for sub in L for _ in xrange(sub_list[0])]

或者：

def por(L):
    return [ele  for times, ele in L for _ in xrange(times)]

使用与您自己的代码类似的东西：

def por(L):
    result = []
    # loop over each sublist
    for sub_list in L:
        # get first sublist element and loop in that range
        times = sub_list[0] # actually accessing the first element of each sublist
        for _ in xrange(times): # use range for python 3
            # here we are adding each sublist element 1 element 0 times
            result.append(sub_list[1])
    return result

在您的代码中，您尝试将L[j]* L[j-1]乘以两个列表，就像您在代码中添加print L[j],L[j-1]时所看到的那样：

[4, 1] [1, 'bonjour']
[2, 2] [4, 1]
[4, 1] [1, 'bonjour']
[2, 2] [4, 1]
[4, 1] [1, 'bonjour']
[2, 2] [4, 1]
[4, 1] [1, 'bonjour']
[2, 2] [4, 1]
[4, 1] [1, 'bonjour']
[2, 2] [4, 1]

Answer 2

也许最简单：

result = []
for repetitions, contents in L:
    for _ in range(repetitions):
        result.append(contents)

是的，有更好的方法，其中一些已经发布，但也许这个的简单性会有所帮助。

避免len调用和索引，有利于循环遍历列表并将其每个项目解压缩到repetitions和content，我觉得有助于简单化;所以从一个重复的append调用的空列表中构建结果，而不是更加惯用但可能更模糊，更初学者使用列表推导和＆amp; c。

Answer 3

我个人觉得itertools可以让我们的生活更容易解决这些问题：

def por(L):
    chains = (itertools.repeat(b, a) for a, b in L)
    return list(itertools.chain_from_iterable(chains))

或者，一行：

>>> list(itertools.chain_from_iterable(itertools.repeat(b, a) for a, b in L))
[1, 1, 1, 1, 2, 2, 'test', 'test', 3, 3, 3, 'bonjour']

Answer 4

>>> L = ([[4,1],[2,2],[2,"test"],[3,3],[1,"bonjour"]])
>>> [y for x, y in  L for i in range(x)]
[1, 1, 1, 1, 2, 2, 'test', 'test', 3, 3, 3, 'bonjour']

TypeError：不能将序列乘以'list'类型的非int

4 个答案: