Search code examples
pythonpython-3.xuser-inputequationdifferential-equations

Python User input equation

I'm writing a simple python script to solve differential equations using Eulers method and right now i have to change the source code every time i want to solve a new equation.

(Safety isn't of any concern at the moment as this is a personal project.)

My question:
Would it be possible to type in an equation as user input and make it to a variable? For example, using e=input("enter equation") where you enter y/x, and making e a variable for later use?

#I would like to be able to type in a equation as user input and turn it to a variable for later use in the if and elif segments, example

    e=input("Enter your equation here")
    e=float(e)


    h=input("Ange steglängd: ")
    h=float(h)

    x=input("Angivet värde på x: ") 
    x=float(x)

    y=input("Värde på y med anseende på x: ") 
    y=float(y)

    z=input("Närmevärde du vill ha för y(x), ange x: ") 
    z=float(z)


    if x<z:
        while x<z:

            #Type in equation below as e

            e=y/x

            y=y+h*e 
            x+=h    

        print(y)

    elif x>z: 
        while x>z:

            e=y/x

            y=y-h*e
            x-=h

        print(y)
Solution

  • Tack för exempel -- that allowed me to determine what you need.

    Yes, this is possible. Read in the equation as a string variable, such as

    equation = input("Enter your equation here")

    Then when you want to find a value for e, use the Python eval method:

    e = eval(equation)

    Be very careful with this method: eval() is powerful, and very discriminating about what it accepts.