python 画散点密度图，设置图例，标题等细节

最初接触python画图的时候，这个散点密度图也是经历了一波三折才做出来。
直接给一个画图的代码，方便有需要的同学做个参考

from statistics import mean
import matplotlib
import matplotlib.pyplot as plt
plt.ion()
from collections import defaultdict
from pandas import set_option
from operator import itemgetter
from sklearn.metrics import explained_variance_score,r2_score,median_absolute_error,mean_squared_error,mean_absolute_error
from matplotlib.colors import LogNorm
from scipy.stats import gaussian_kde
from scipy import stats

def scatter_out_1(x, y, title_name, savename): ## x,y为两个需要做对比分析的两个量。
    # ==========计算评价指标==========
    BIAS = mean(x - y)
    MSE = mean_squared_error(x, y)
    RMSE = np.power(MSE, 0.5)
    R2 = r2_score(x, y)
    MAE = mean_absolute_error(x, y)
    EV = explained_variance_score(x, y)

    print('==========算法评价指标===