英文:
how do i have sympy yield `{1, 2}` given an positive integer `x < 3`
问题
我正在尝试使用 `sympy.solve` 解决一个不等式，以下是代码部分：
```python
from sympy import Symbol, solve
x = Symbol('x', positive=True, integer=True)
ineq1 = x - 3 < 0
solution = solve((ineq1), x)
print(solution)
上面的程序得到了 x < 3 的结果。虽然这个结果是合理的，但我想得到一个包含整数 1 和 2 的集合 {1, 2}。
我该如何实现这一点？
<details>
<summary>英文:</summary>
I'm trying to solve an inequality using `sympy.solve`, here is the code
```python
from sympy import Symbol, solve
x = Symbol('x', positive=True, integer=True)
ineq1 = x - 3 < 0
solution = solve((ineq1), x)
print(solution)
The program above yields x < 3. The result makes sense though, i'd like to get a set that consists of 2 integers 1 and 2, {1, 2}.
how do i achieve that?
答案1
得分: 1
单变量不等式可以通过集合来处理，集合交集可以限制结果为正整数：
from sympy import Range, oo, S, And
ineq1.as_set().intersection(Range(1, oo))
{1, 2}
你也可以用S.Naturals替代Range(1, oo)。你还可以使用复合表达式，并将其集合与S.Integers相交：
And(x > 0, x < 3).as_set().intersection(S.Integers)
{1, 2}
英文:
A univariate inequality can be handled by Sets and Set intersection can limit the result to positive integers:
>>> from sympy import Range, oo, S, And
...
>>> ineq1.as_set().intersection(Range(1,oo))
{1, 2}
You can also replace Range(1,oo) with S.Naturals. You can also use a compound expression and intersect its set with S.Integers:
>>> And(x>0,x<3).as_set().intersection(S.Integers)
{1, 2}
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