How to get color of most recent plotted line in Python's plt

Question

I plot a line without specifying the color (think: plt.plot(x,y)). Say the color comes out blue.

Question: How do I obtain this color from the plt object so that I can put it into a variable?

Seems like this is close (and potentially the solution):

p = plt.plot(x,y)
color = p[0].get_color()

Updated question: I am not sure I understand the "0" index: Does p[0] always access the most recent plotted line?

Answer 1

If you cannot access or store the return value of the call to plt.plot, you should also be able to use plt.gca().lines[-1].get_color() to access the color of the last line which was added to the plot.

In the following example, I'm creating example data, run curve_fit and show both data and fitted curve in the same color.

import matplotlib.pyplot as plt
import numpy as np
from scipy.optimize import curve_fit

m = 5
n = 3
x = np.arange(m)
y = np.array([i * x + np.random.normal(0, 0.2, len(x)) for i in range(n)])

def f(x, a, b):
    return a * x + b

for y_i in y:
    popt, pcov = curve_fit(f, x, y_i)
    plt.plot(x, y_i, linestyle="", marker="x")
    plt.plot(x, f(x, *popt), color=plt.gca().lines[-1].get_color())
plt.show()

Answer 2

For regular plt.plot, doing item.get_color() on each element of the list it returns will get you the colors of each line.

But other plot functions, like plt.scatter, will return a Collection. For a Collection, you can call result.get_facecolor(). This will return an array of color values of the foreground colors of the elements. So if they're all the same color (as they are when you make a scatter plot with just X and Y values), result.get_facecolor()[0] will suffice.