从字符串到sympy表达式

Question

最近我正在使用Flask和sympy库开发Web应用程序。用户在textarea中输入他的公式，Flask将它作为一个字符串实现。我希望有可能通过使用sympy函数solve（）来计算这个方程的结果。但为此，我必须将此字符串转换为sympy表达式。我怎么能这样做？

`

from flask import Flask,request,render_template,flash 
from sympy import * 
from sympy.parsing.sympy_parser import * 

x = symbols('x') 
app = Flask(__name__) 
app.secret_key = 'mysecretkey' 


def calculate_(): 
    first_eq = request.form['first_eq'] 

    first_eq2= parse_expr(first_eq) 
    result = solve(first_eq2) 
    return result 


@app.route("/",methods=['GET', 'POST']) 
def myGet(): 

    return render_template("my-form.html") 

@app.route("/myPost/",methods=['GET', 'POST']) 
def myPost(): 
    answer = request.form['answer'] 
    result_of_answer=solve(Eq(answer),x) 
    result = calculate_() 
    try: 
     if result == result_of_answer: 
      flash("you got it!") 
     else: 
      flash("no, it's wrong") 
      return render_template("my-form.html") 
    except: 
     flash("sorry, wrong type. Try again!") 
     return render_template("my-form.html") 
if __name__ == '__main__': 
    app.run()` 

Answer 1

你要找的功能是sympify。 http://docs.sympy.org/latest/modules/core.html#sympy.core.sympify.sympify