如何使用python中的sympy来计算表达式 [英] How to calculate expression using sympy in python

问题描述

我需要在python中使用sympy来计算以下表达式？

I need a calculate below expression using sympy in python?

exp = '(a+b)*40-(c-a)/0.5'

在 a = 6 ， b = 5 ， c = 2 这种情况下如何使用python中的sympy来计算表达式？请帮助我。

In a=6, b=5, c=2 this case how to calculate expression using sympy in python? Please help me.

推荐答案

文档在这里： http://docs.sympy.org/ 。你应该真正阅读它！

The documentation is here: http://docs.sympy.org/. You should really read it!

要计算你的表达式，写下这样的东西：

To "calculate" your expression, write something like this:

from sympy import Symbol
a = Symbol("a")
b = Symbol("b")
c = Symbol("c")
exp = (a+b)*40-(c-a)/0.5

就是这样。如果你的意思是计算，你也可以解决exp = 0：

And that's it. If you meant something else by "calculate", you could also solve exp = 0:

sympy.solve(exp)
> {a: [0.0476190476190476*c - 0.952380952380952*b],
>  b: [0.05*c - 1.05*a],
>  c: [20.0*b + 21.0*a]}

对于其他一切，你应该真正阅读文档。也许从这里开始： http://docs.sympy.org/0.7.1/tutorial .html＃tutorial

For everything else, you should really read the docs. Maybe start here: http://docs.sympy.org/0.7.1/tutorial.html#tutorial

更新：由于您将a，b，c的值添加到该问题中，您可以将其添加到解决方案中： p>

UPDATE: since you added the values for a, b, c to the question, you can add this to the solution:

exp.evalf(subs={a:6, b:5, c:2})

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