matplotlib画三维柱形图只有画布没有柱

##想要画三维柱形图，但是只有画布没有柱，这是肿么回事很懵逼，求解惑
##数据是经济指标

GGdp=enco[(enco['Series Name']=='GDP（现价美元）')&
          ((enco['Country Name']=='中国')
           |(enco['Country Name']=='日本')
           |(enco['Country Name']=='大韩民国')
           |(enco['Country Name']=='俄罗斯联邦')
           |(enco['Country Name']=='英国')
         |(enco['Country Name']=='法国')
           |(enco['Country Name']=='德国')
        |(enco['Country Name']=='美国'))]
Time=[2012,2013,2014,2015,2016,2017,2018,2019,2020]
G=np.array(GGdp[['2012 [YR2012]','2013 [YR2013]','2014 [YR2014]','2015 [YR2015]','2016 [YR2016]','2017 [YR2017]','2018 [YR2018]','2019 [YR2019]','2020 [YR2020]']].values.tolist())


from mpl_toolkits.mplot3d.axes3d import Axes3D

fig=plt.figure(figsize=(9,6))
ax=plt.subplot(111,projection='3d')


for i in range (0,8):
    a=[i]*10
    gp=G[i]
    
    ax.bar3d=(a,range(9),a,
         0.1,0.1,gp,"#0000FF"
          )

ax.set_xticks([0,1,2,3,4,5,6,7])
ax.set_xticklabels(['CH','JA','KO','RU','UK','FR','DE','US'])

ax.set_yticks([0,1,2,3,4,5,6,7,8])
ax.set_yticklabels([2012,2013,2014,2015,2016,2017,2018,2019,2020])

ax.set_zlabel('GDP')
plt.show()