Matplotlib animation doesn't clear previous frame before plotting new one

So, I'm trying to create an animated plot, but I want the previous frame to be cleared before a new one appears. What I keep getting is all frames at the same time or just a blank plot.

fig, ax = plt.subplots()

campo = ax.plot(x2[0], phiSol[0])[0]

def init():
    campo.set_data([],[])
    return campo

def update(frame):
    campo.set_xdata(x2[:frame])
    campo.set_ydata(phiSol[:frame])

    return campo

anima = ani.FuncAnimation(fig=fig, func=update, init_func=init, frames=40, interval=30)
HTML(anima.to_jshtml())

I tried to build an init_func, but none of my tries worked. The last try is that one in the above code. How could I do it?

It's your slicing that's causing the problem. with :frame you're slicing up to frame instead of just grabbing the frame you want. You may have copied an example with a moving point that traces out a line .

I just tried this, and it worked how you described.

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.animation import FuncAnimation

# a sin wave, moving through space (test data)
x2 = np.linspace(0, 2*np.pi, 100)
phiSol = np.array([np.sin(x2 + phase) for phase in np.linspace(0, 2*np.pi, 60)])  

fig, ax = plt.subplots()
ax.set_xlim(np.min(x2), np.max(x2))
ax.set_ylim(np.min(phiSol), np.max(phiSol))

campo, = ax.plot([], [])

def init():
    campo.set_data([], [])
    return campo,

def update(frame):
    campo.set_data(x2, phiSol[frame])
    return campo,

ani = FuncAnimation(fig, update, frames=len(phiSol), init_func=init, blit=True) # blit=True not necessary, but can optimize the animation.
plt.show()

Without the axis limits, mine was showing me an empty window, so you can try removing that and see how it goes, and add something similar if you have problems. I added a couple options to make it a bit better (campo,) to retrieve only the first thing returned by ax.plot instead of a list of objects, and blit=True which can optimize the creation of the animation if it gets slow (see FuncAnimation docs).