TypeError: 'numpy.ndarray' object is not callable , where does it take an array from?

def draw_PF(g, x0, nb, colors):    
    plt.plot([x0], [x0], color = colors, marker='o')
    for i in range(nb):
        x1 = g(x0)
        plt.plot([x0,x0], [x0,x1], color = colors)
        plt.plot([x0,x1], [x1,x1], color = colors)
        x0 = x1

x = np.linspace(0,1,999)
y1 = 1-np.sin(𝑥)
y2 = np.exp(-4*x)
y3 = 0.4 * np.exp(𝑥) - 0.25
y4 = 1/(1 + ((1-x)/x)**2)
y = x
y1_dev = -np.cos(x)
y2_dev = -4 * y2
y3_dev = 0.4*np.exp(x)
y4_dev = 2*((1 + ((1-x)/x)**2)**-2)*((1-x)/x**3)
functions = [y1,y2,y3,y4]
derivatives = [y1_dev,y2_dev,y3_dev,y4_dev]
iterations = [10,10,10,10]
colors = ["r","g","c","m"]
fixed_points = [0.5,0.3,0.3,0.5]
for i in range(len(functions)):
    plt.plot(x,functions[i])
    plt.plot(x,y)
    plt.show()
for j in range(len(derivatives)):
    plt.plot(x,derivatives[j])
    plt.show()

for k in range(len(functions)):
    dessiner_PF(functions[k],(fixed_points[k] - 0.1), iterations[k], couleurs[k])
    plt.show()
TypeError                                 Traceback (most recent call last)
Cell In[28], line 25
     22     plt.show()
     24 for k in range(len(functions)):
---> 25     draw_PF(functions[k],(fixed_points[k] - 0.1), iterations[k], colors[k])
     26     plt.show()

Cell In[27], line 15, in draw_PF(g, x0, nb, colors)
     13 plt.plot([x0], [x0], color = colors, marker='o')
     14 for i in range(nb):
---> 15     x1 = g(x0)
     16     plt.plot([x0,x0], [x0,x1], color = colors)
     17     plt.plot([x0,x1], [x1,x1], color = colors)

TypeError: 'numpy.ndarray' object is not callable``

'Hello, I keep receiving this error message, but i dont understand quite why...
I am trying to implement a Picard algorithm to find fix points, but I keep having an issue with my call, I especially don't understand from where it takes the numpy array... thank you in advance.'

The error comes from this function:

def draw_PF(g, x0, nb, colors):    
    plt.plot([x0], [x0], color = colors, marker='o')
    for i in range(nb):
        x1 = g(x0)  # error is here
        plt.plot([x0,x0], [x0,x1], color = colors)
        plt.plot([x0,x1], [x1,x1], color = colors)
        x0 = x1

g(x0) does not work because g itself is not defined as a function in your code. If you do print(g) you get a numpy.ndarray with the shape (999,). This is because you define y1, which is the first object representing g in draw_PF, as follows:

x = np.linspace(0,1,999)
y1 = 1-np.sin(x)

Since y1 is a numpy array, it is not callable (that is to say it does not behave like a function since it's an array) and therefore python returns you this error numpy.ndarray' object is not callable. The same applies for y2, y3, and y4.

Let me know if this helped!

There's not enough information to know for sure, but it seems like g is a np.ndarray, and you're trying to access element x0. In that case, you want g[x0], to access the x0'th element of the list.