问题描述
除了Python在列表之间具有可变状态外，我还有很多类似Python中的列表理解的功能.有什么办法可以通过列表理解吗?
I have something which is an awful lot like a list comprehension in Python, except that it shares mutable state between iterations. Is there any way to do it with a list comprehension?
def f(x):
""" 5-bit LFSR """
return (x >> 1) ^ (0x12*(x&1))
def batch(f, x, n):
result = [x]
for _ in xrange(1,n):
x = f(x)
result.append(x)
return result
batch(f, 1, 5)
返回[1, 18, 9, 22, 11].这里重要的是batch函数，而不是f(x)，这里只是一个简单的示例来说明问题.
which returns [1, 18, 9, 22, 11]. Here the important thing is the batch function, not f(x) which is here just a simple example to illustrate the issue.
或者我可以使用生成器来实现:
Alternatively I could implement using a generator:
def batch(f, x, n):
yield x
for _ in xrange(1,n):
x = f(x)
yield x
list(batch(f, 1, 5))
但是闻起来有点尴尬.我正在寻找的是这样的东西...
But it smells a little awkward. What I'm looking for is something like this...
batch = [??? for _ in xrange(n)]
推荐答案
否.故意没有.最终，他们放入了itertools.accumulate，这与以功能方式实现递归关系的官方推荐方法最接近，但在2.7中不存在.您可以从 docs 如果需要的话.
No. Deliberately no. Eventually they put in itertools.accumulate, which is the closest thing to an Officially Recommended way to implement recurrence relations in a functional manner, but it doesn't exist on 2.7. You could copy the "roughly equivalent to" Python implementation from the docs if you want.
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