Python 具有递减值的产品

我有三个清单：

a = [10, 9, 8, 7, 6]
b = [8, 7, 6, 5, 4, 3]
c = [6, 5, 4, 3, 2]

我需要获得使用itertools.product获得的所有排列，但仅当值正在减小时：

[10, 8, 6] # is good
[6, 8, 4]  # is not good, since 8 > 6

---

有一种简单的方法吗？或者我应该使用列表理解和条件吗？

您可以使用列表理解通过在Itertools.product迭代器上循环并仅提取按相反顺序排序的返回项来实现这一点：

[item for item in product(a,b,c) if sorted(item, reverse = True) == list(item)]

例如：

from itertools import product
a = [10,9,8,7,6]
b = [8, 7, 6, 5, 4, 3]
c = [6, 5, 4, 3, 2]
[item for item in product(a,b,c) if sorted(item, reverse = True) == list(item)]
# [(10, 8, 6), (10, 8, 5), (10, 8, 4), (10, 8, 3), (10, 8, 2) ...continues

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您可以通过列表理解来做到这一点，方法是在Itertools.product迭代器上循环，并仅提取按相反顺序排序的返回项：

[item for item in product(a,b,c) if sorted(item, reverse = True) == list(item)]

例如：

from itertools import product
a = [10,9,8,7,6]
b = [8, 7, 6, 5, 4, 3]
c = [6, 5, 4, 3, 2]
[item for item in product(a,b,c) if sorted(item, reverse = True) == list(item)]
# [(10, 8, 6), (10, 8, 5), (10, 8, 4), (10, 8, 3), (10, 8, 2) ...continues

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这是一个简单的单线解决方案

>>> mylist = [10, 9, 8, 7, 6]
>>> all(earlier >= later for earlier, later in zip(mylist, mylist[1:]))
True
>>> mylist = [10, 9, 7, 8, 6]
>>> all(earlier >= later for earlier, later in zip(mylist, mylist[1:]))
False

我在这里找到了这个：

---

这是一个简单的单线解决方案

>>> mylist = [10, 9, 8, 7, 6]
>>> all(earlier >= later for earlier, later in zip(mylist, mylist[1:]))
True
>>> mylist = [10, 9, 7, 8, 6]
>>> all(earlier >= later for earlier, later in zip(mylist, mylist[1:]))
False

我在这里找到了这个：

---

如果出于某种原因不想使用列表理解：

def decreasing(l):
    return all(a >= b for a, b in zip(l[:-1], l[1:]))


filter(decreasing, product(a, b, c))

---

如果出于某种原因不想使用列表理解：

def decreasing(l):
    return all(a >= b for a, b in zip(l[:-1], l[1:]))


filter(decreasing, product(a, b, c))

---

您可以引用以下没有列表理解的代码：

from itertools import product
a = [10, 9, 8, 7, 6]
b = [8, 7, 6, 5, 4, 3]
c = [6, 5, 4, 3, 2]
for result in product(a,b,c):
    if sorted(result, reverse = True) == list(result):
            print result

---

您可以引用以下没有列表理解的代码：

from itertools import product
a = [10, 9, 8, 7, 6]
b = [8, 7, 6, 5, 4, 3]
c = [6, 5, 4, 3, 2]
for result in product(a,b,c):
    if sorted(result, reverse = True) == list(result):
            print result