python 蟒蛇| 如何将元素随机附加到列表中
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Python | How to append elements to a list randomly
提问by Switch
Is there a way to append elements to a list randomly, built in function
有没有办法将元素随机附加到列表中，内置函数
ex:
前任：
def random_append():
lst = ['a']
lst.append('b')
lst.append('c')
lst.append('d')
lst.append('e')
return print lst
this will out put ['a', 'b', 'c', 'd', 'e']
这将输出 ['a', 'b', 'c', 'd', 'e']
But I want it to add elements randomly and out put something like this:
['b', 'd', 'b', 'e', 'c']
但我希望它随机添加元素并输出如下内容：
['b', 'd', 'b', 'e', 'c']
And yes there's a function random.shuffle() but it shuffles a list at once which I don't require, I just want to perform random inserts only.
是的，有一个函数 random.shuffle() 但它一次洗牌一个我不需要的列表，我只想执行随机插入。
采纳答案by Ants Aasma
If you need to perform single insert in a random position then the already given trivial exapmle works:
如果您需要在随机位置执行单个插入，那么已经给出的简单示例可以工作：
from random import randrange, sample
def random_insert(lst, item):
lst.insert(randrange(len(lst)+1), item)
However if you need to insert k items to a list of length n then using the previously given function is O(n*k + k**2) complexity. However inserting multiple items can be done in linear time O(n+k) if you calculate the target positions ahead of time and rewrite the input list in one go:
但是，如果您需要将 k 个项目插入到长度为 n 的列表中，那么使用前面给出的函数的复杂度为 O(n*k + k**2)。但是，如果您提前计算目标位置并一次性重写输入列表，则可以在线性时间 O(n+k) 内插入多个项目：
def random_insert_seq(lst, seq):
insert_locations = sample(xrange(len(lst) + len(seq)), len(seq))
inserts = dict(zip(insert_locations, seq))
input = iter(lst)
lst[:] = [inserts[pos] if pos in inserts else next(input)
for pos in xrange(len(lst) + len(seq))]
回答by John La Rooy
If there is supposed to be exactly one of each item
如果每个项目应该只有一个
>>> from random import randint
>>> a=[]
>>> for x in "abcde":
... a.insert(randint(0,len(a)),x)
...
>>> a
['b', 'a', 'd', 'c', 'e']
If you are allowing duplicates (as the output indicates)
如果您允许重复（如输出所示）
>>> from random import choice
>>> a=[choice("abcde") for x in range(5)]
>>> a
['a', 'b', 'd', 'b', 'a']
回答by Mike Graham
random.shuffleis probably the best tool for the job. It is simple, obvious, and well-named—it's probably more readable than the other suggestions you will get. Additionally, using it is O(n), but using insert(an O(n) operation) n times is quadratic.
random.shuffle可能是这项工作的最佳工具。它简单、明显且命名良好——它可能比您将获得的其他建议更具可读性。此外，使用它是 O(n)，但使用insert（一个 O(n) 操作）n 次是二次的。
回答by Luka Rahne
from random import choice
n=10
seq=['a','b','c','d']
rstr=[choice(seq) for i in range(n)]
