最近我使用Flask和sympy库开发了一个Web应用程序。用户在textarea中输入他的等式，Flask将其作为字符串取代。我想通过使用sympy函数solve（）来计算这个等式的结果。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()`