So, if I do this
所以，如果我这样做
import sympy as sp
import numpy as np
u = np.random.uniform(0, 1, 10)
w, k = sp.symbols('w k')
l = sum(1 - sp.log(k + w) + sp.exp(k + w) for k in u)
I get what I want (a symbolic sum over u as a function of w). However, it would be much more useful to write
我得到了我想要的东西（作为w的函数的象征性的总和）。但是，编写它会更有用
f = 1 - sp.log(k + w) + sp.exp(k + w)
l = sum(f for k in u)
But then I get
但后来我明白了
10*exp(k + w) - 10*log(k + w) + 10
What's going on? Is there a way to get the sum I want? (SymPy has several ways of summing over integers, but I haven't found one for arrays) (Version: Python 2.7.6, NumPy 1.8.1, SymPy 0.7.4.1)
这是怎么回事？有没有办法得到我想要的金额？ （SymPy有几种求和整数的方法，但我没有找到一个用于数组的方法）（版本：Python 2.7.6，NumPy 1.8.1，SymPy 0.7.4.1）
2 个解决方案
#1
2
The problem is that f is not being evaluated for each k. Try this out:
问题是没有为每个k评估f。试试这个：
sum([f.subs(dict(k=k)) for k in u])
and it will give you the right result. Where subs() is being used to force the evaluation of f for each value of k.
它会给你正确的结果。其中subs（）用于强制评估每个k值的f。
#2
0
Making f a function that returns the resulting calculation is what needs to happen here to make it work the way you have it.
使f成为返回结果计算的函数是需要在此处进行的，以使其按照您的方式工作。
f = lambda k,w : 1 - sp.log(k + w) + sp.exp(k + w)
l = sum(f(k,w) for k in u)
#1
2
The problem is that f is not being evaluated for each k. Try this out:
问题是没有为每个k评估f。试试这个：
sum([f.subs(dict(k=k)) for k in u])
and it will give you the right result. Where subs() is being used to force the evaluation of f for each value of k.
它会给你正确的结果。其中subs（）用于强制评估每个k值的f。
#2
0
Making f a function that returns the resulting calculation is what needs to happen here to make it work the way you have it.
使f成为返回结果计算的函数是需要在此处进行的，以使其按照您的方式工作。
f = lambda k,w : 1 - sp.log(k + w) + sp.exp(k + w)
l = sum(f(k,w) for k in u)