python的matplotlib城市空气指数图

import numpy as np
import pandas as pd
import matplotlib
import matplotlib.pyplot as plt
#读取文件，去掉无用字段
bj_data=pd.read_csv('./beijing.csv').drop(['PM_Dongsi','PM_Dongsihuan','PM_Nongzhanguan','DEWP','HUMI','PRES','TEMP','cbwd','Iws','precipitation','Iprec'],axis=1)#                                                                                                    'ation','Iprec')
#数据清洗
bj_data.drop(bj_data[np.isnan(bj_data['PM_US Post'])].index,inplace=True)
def get_level(pm_us):
    if pm_us < 35:
        return '优'
    elif pm_us <75:
        return '良'
    elif pm_us <150:
        return '轻度污染'
    elif pm_us <200:
        return '中度污染'
    elif pm_us<250:
        return '重度污染'
#给原始数据添加新列level
bj_data.loc[:,'level']=bj_data['PM_US Post'].apply(get_level)
print(bj_data)
#统计各种空气质量掉比例
bj_level=bj_data.groupby(['level']).size()/len(bj_data)
#画图
matplotlib.rcParams['font.sans-serif'] = 'SimHei'
l=['中度污染','优','良','轻度污染','重度污染']
plt.pie(bj_level,labels=l,autopct='%.2f%%')
plt.title('空气污染指数')
plt.show()