我正在处理多项式并且必须执行一些操作，其中我的循环变量的总和低于某个常量 d。 现在我有
for i in range(0, d):
for j in range(i, d):
for k in range(j, d):
我觉得有点丑。 是否有一些功能，可能在 itertools 中，允许我迭代 for i, j, k in foo(d) ？
请您参考如下方法:
你可以自己写。这是 3 个变量的蛮力方法:
def constant_sum(s):
for i in range(s+1):
for j in range(s-i+1):
k = s - i - j
yield i,j,k
def inferior_sum(s):
for i in range(s+1):
for j in range(s+1):
if i+j >= s:
break
for k in range(s+1):
if i+j+k < s:
yield i,j,k
else:
break
for i,j,k in constant_sum(3):
print(i,j,k)
print()
for i,j,k in inferior_sum(3):
print(i,j,k)
输出:
0 0 3
0 1 2
0 2 1
0 3 0
1 0 2
1 1 1
1 2 0
2 0 1
2 1 0
3 0 0
0 0 0
0 0 1
0 0 2
0 1 0
0 1 1
0 2 0
1 0 0
1 0 1
1 1 0
2 0 0
这里是递归版本，可以为任何总和做任意数量的变量(n)...轻微测试:
def constant_sum(n,s):
if n == 1:
yield [s]
else:
for i in range(s+1):
for r in constant_sum(n-1,s-i):
yield [i] + r
def inferior_sum(n,s):
if n == 1:
for i in range(s):
yield [i]
else:
for i in range(s):
for r in inferior_sum(n-1,s-i):
yield [i] + r
for x in constant_sum(3,3):
print(*x)
print()
for x in inferior_sum(3,3):
print(*x)
输出:
0 0 3
0 1 2
0 2 1
0 3 0
1 0 2
1 1 1
1 2 0
2 0 1
2 1 0
3 0 0
0 0 0
0 0 1
0 0 2
0 1 0
0 1 1
0 2 0
1 0 0
1 0 1
1 1 0
2 0 0
