python 实现在一张图中绘制一个小的子图方法

import matplotlib.pyplot as pltimport MySQLdb as mdbimport numpy as npfrom mpl_toolkits.axes_grid1.inset_locator import inset_axesfrom mpl_toolkits.axes_grid1.inset_locator import mark_insetdef graph():  # 连接数据库  conn = mdb.connect(host='127.0.0.1', port=3306, user='root', passwd='root', db='alibaba_trace', charset='utf8')  # 如果使用事务引擎，可以设置自动提交事务，或者在每次操作完成后手动提交事务conn.commit()  conn.autocommit(1) # conn.autocommit(True)  # 使用cursor()方法获取操作游标  cursor = conn.cursor()  # 因该模块底层其实是调用CAPI的，所以，需要先得到当前指向数据库的指针。  try:    cursor.execute("select machineID, count(id) from batch_instance where machineID != 0 group by machineID")    records = cursor.fetchall()    list_records = list(records)  except:    import traceback    traceback.print_exc()    # 发生错误时回滚    conn.rollback()  finally:    # 关闭游标连接    cursor.close()    # 关闭数据库连接    conn.close()  res = []  res[:] = map(list, list_records)  machineID = [x[0] for x in res]  instance_num = [x[1] for x in res]  print(max(instance_num))  print(min(instance_num))  fig = plt.figure()  ax1 = fig.add_subplot(1, 1, 1)  # # cdf  # hist, bin_edges = np.histogram(instance_num, bins=len(np.unique(instance_num)))  # cdf = np.cumsum(hist / sum(hist))  # ax1.plot(bin_edges[1:], cdf, color='red', ls='-')  # ax1.set_xlabel("instance number per machine")  # ax1.set_ylabel("portion of machine")  # plt.savefig('../../imgs_mysql/cdf_of_machine_instance.png')  # # 直方图  ax1.hist(instance_num, normed=False, alpha=1.0, bins=100)  ax1.set_xlabel('instance number per machine')  ax1.set_ylabel('machine number')  # cdf 要添加的子图  axins = inset_axes(ax1, width=1.5, height=1.5, loc='upper left')  # ax1 大图  # width height分别为子图的宽和高  # loc 为子图在大图ax1中的相对位置 相应的值有  # upper left  # lower left  # lower right  # right  # center left  # center right  # lower center  # upper center  # center  hist, bin_edges = np.histogram(instance_num, bins=len(np.unique(instance_num)))  cdf = np.cumsum(hist / sum(hist))  axins.plot(bin_edges[1:], cdf, color='red', ls='-')  axins.set_yticks([])  # axins.set_xlabel("instance number per machine")  # axins.set_ylabel("portion of machine")  plt.savefig("../../imgs_mysql/hist_of_machine_instance")  plt.show()if __name__ == '__main__':  graph()