Sympy 似乎无法简化涉及变量平方根的表达式:
在[28]中:a = x**2在[29]中:b = a**(1/2)在 [30] 中:b出[30]:0.5⎛ 2⎞⎝x ⎠在 [31] 中:b.simplify()出[31]:0.5⎛ 2⎞⎝x ⎠我不认为它适用于 simplify 的其他变体,特别是我认为 b.powsimp() 应该可以工作.
在[32]中:b.powsimp()出[32]:0.5⎛ 2⎞⎝x ⎠有谁知道为什么这不起作用,或者我做错了什么?
解决方案你的例子有两个问题.
第一个 sqrt(x**2)==x 仅用于 正 实数.
其次,对于 SymPy 1/2 和 0.5 不是一回事.第一个是 Rational 实例,第二个是 float 实例.
最后一个例子:
>>>x = Symbol('x', real=True)>>>(x**2)**(1./2)∣x∣**1.0>>>(x**2)**(S(1)/2) # S() 是 sympify() 的缩写∣x∣sympify 将 python 对象转换为更合适的 SymPy 对象.
Sympy does not seem to be able to simplify an expression where the square root of a square of a variable is involved:
In [28]: a = x**2 In [29]: b = a**(1/2) In [30]: b Out[30]: 0.5 ⎛ 2⎞ ⎝x ⎠ In [31]: b.simplify() Out[31]: 0.5 ⎛ 2⎞ ⎝x ⎠I do not get this to work with other variants of simplify, in particular I would have thought that b.powsimp() should work.
In [32]: b.powsimp() Out[32]: 0.5 ⎛ 2⎞ ⎝x ⎠Does anyone know why this does not work, or what I am doing wrong?
解决方案There are two problems with your example.
First sqrt(x**2)==x only for positive real numbers.
Second, for SymPy 1/2 and 0.5 are not the same things. The first is a Rational instance, the second is a float instance.
Finally, an example:
>>> x = Symbol('x', real=True) >>> (x**2)**(1./2) ∣x∣**1.0 >>> (x**2)**(S(1)/2) # S() is short for sympify() ∣x∣sympify transforms python objects to more adequate SymPy objects.
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