How to set Timestamp (pandas Datetime) to xlim of plot with FunctAnimation?

Question

I want to limit my graph from left and set (the current time - 2 hours) to xlim. I tried to add to the "update" function this

self.ax.set_xlim(left=max(self.data.iloc[0, 0], self.data.iloc[-1, 0] - pd.Timedelta(hours=2)))

But this is doesn't work. Could anyone help me do this, please?

from matplotlib import pyplot as plt
from matplotlib.animation import FuncAnimation
from datetime import datetime
import pandas as pd

def to_pd(wt, wf):
    p = pd.DataFrame({"Date": [wt], "Cost": [wf]})
    p["Date"] = pd.to_datetime(p["Date"], format='%Y-%m-%d %H:%M:%S')
    return p


fig = plt.figure(figsize=(18,8), dpi=90)

class Graph():
    def __init__(self):
        self.ax = fig.add_subplot()
        self.start_time = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
        self.data = to_pd(self.start_time,0)
        self.line, = self.ax.plot(self.data.Date,self.data.Cost)

    def update(self,i):
        self.current_time = (self.data.iloc[-1,0]+pd.Timedelta(minutes=1)).strftime('%Y-%m-%d %H:%M:%S')
        self.data = self.data.append(to_pd(self.current_time,(-1)**i))

        self.line.set_data(self.data.Date, self.data.Cost)

        self.ax.relim()
        self.ax.autoscale_view()

        return self.line,

object = Graph()
def animate(i):
    return object.update(i)

anim = FuncAnimation(fig, animate, frames=200,interval=100, blit=True)
plt.show()

Answer 1

Solved, but I think there is more convenient way. But, here what am done, just added it into the 'update' function, it's clear all old data:

if self.data.iloc[-1, 0] - pd.Timedelta(hours=2) >= self.data.iloc[0, 0]:
    self.data = self.data[self.data.Date > self.data.iloc[0, 0]]