python连oanda的模拟交易api画走势图第八问

Question

我想画外汇实时走势图，如下是我的程序：

import matplotlib.pyplot as plt
import requests
import json
import traceback

plt.close()  #clf() # 清图  cla() # 清坐标轴 close() # 关窗口
fig=plt.figure()
ax=fig.add_subplot(1,1,1)
ax.axis("equal") #设置图像显示的时候XY轴比例
plt.grid(True) #添加网格

plt.ion()  #互动模式开始

url = "https://api-fxpractice.oanda.com/v1/prices"
instruments = 'EUR_USD,USD_CAD'
account_id = 'cawa11'
params = {'instruments':instruments,'accountId':account_id}
access_token = 'a554db3a48ac8180a6996a5547ba1663-ac5947e64456cc5842a34f4ce05e4380' 
headers = {'Connection': 'Keep-Alive',
           'Accept-Encoding': 'gzip,deflate',
           'Authorization':'Bearer '+access_token}

time = 0

try:
    while True:
        
        r = requests.get(url,headers = headers, params=params)
        price = r.json()

        obsX = time #price['prices'][0]['time']
        time = time + 1
        
        obsY = round((price['prices'][0]['ask']+price['prices'][0]['bid'])/2,5) #EUR/USD中间价
        
        ax.scatter(obsX,obsY,c='b',marker='.')  #散点图
        
        plt.pause(0.0001)
        
except:
    print(traceback.format_exc())
    pass

我遇到的问题是：
1.报错：

Warning (from warnings module):
File "C:Python34libsite-packagesmatplotlibbackend_bases.py", line 2445
warnings.warn(str, mplDeprecation)
MatplotlibDeprecationWarning: Using default event loop until function specific to this GUI is implemented

2.显示不出应有的效果，我希望一开始的0点不在中间而在最左边，可能是ax.axis("equal")的问题

请大家帮助，谢谢