I'm getting the error
我收到了错误
sympy.polys.polyerrors.GeneratorsNeeded: can't initialize from 'dict' without generators
sympy.polys.polyerrors.GeneratorsNeeded：无法在没有生成器的情况下从'dict'初始化
when I try to sum a zero polynomial. The error occurs at the line
当我尝试求零多项式时。错误发生在该行
g = k*Sum(f,(m,k,n)).doit()
Here m and n are symbols, and k is an int. The error occurs the first time through the loop, when f has been initialized to Poly(0,m). The script computes a sequence of polynomials. If instead I initialize f to Poly(m,m) the script runs to completion. If I try Poly(1,m) I get the same error as before.
这里m和n是符号，k是int。当f初始化为Poly（0，m）时，第一次通过循环时会发生错误。该脚本计算一系列多项式。相反，如果我将f初始化为Poly（m，m），脚本将运行完成。如果我尝试Poly（1，m），我会得到与以前相同的错误。
How can I define a constant polynomial so that my script will execute properly?
如何定义常量多项式以便我的脚本正确执行？
1 个解决方案
#1
1
The Sum passes doit() to the object it is trying to sum, which is where the error occurs. So, a minimal example is
Sum将doit（）传递给它试图求和的对象，这是发生错误的地方。所以，一个最小的例子是
x = symbols('x')
f = Poly(0, x)
f.doit() # GeneratorsNeeded: can't initialize from 'dict' without generators
Looks like a bug, an edge case not being addressed correctly. But there is a workaround: pass an expression to Sum (which is what it expects anyway), not a Poly object. A Poly is turned into an expression with as_expr().
看起来像一个错误，边缘情况没有得到正确处理。但是有一个解决方法：将表达式传递给Sum（无论如何都是它所期望的），而不是Poly对象。使用as_expr（）将Poly转换为表达式。
f = Poly(0, m)
Sum(f.as_expr(), (m, 0, n)).doit() # 0
#1
1
The Sum passes doit() to the object it is trying to sum, which is where the error occurs. So, a minimal example is
Sum将doit（）传递给它试图求和的对象，这是发生错误的地方。所以，一个最小的例子是
x = symbols('x')
f = Poly(0, x)
f.doit() # GeneratorsNeeded: can't initialize from 'dict' without generators
Looks like a bug, an edge case not being addressed correctly. But there is a workaround: pass an expression to Sum (which is what it expects anyway), not a Poly object. A Poly is turned into an expression with as_expr().
看起来像一个错误，边缘情况没有得到正确处理。但是有一个解决方法：将表达式传递给Sum（无论如何都是它所期望的），而不是Poly对象。使用as_expr（）将Poly转换为表达式。
f = Poly(0, m)
Sum(f.as_expr(), (m, 0, n)).doit() # 0