graphing an equation with matplotlib

Question

I\'m trying to make a function that will graph whatever formula I tell it to.

import numpy as np  
import matplotlib.pyplot as plt  
def graph(formula, x_range):         


        

Answer 1

This is because in line

graph(x**3+2*x-4, range(-10, 11))

x is not defined.

The easiest way is to pass the function you want to plot as a string and use eval to evaluate it as an expression.

So your code with minimal modifications will be

import numpy as np  
import matplotlib.pyplot as plt  
def graph(formula, x_range):  
    x = np.array(x_range)  
    y = eval(formula)
    plt.plot(x, y)  
    plt.show()

and you can call it as

graph('x**3+2*x-4', range(-10, 11))