Matplotlib： No handles with labels found to put in legend.

[songdg]

plt.legend()提示 No handles with labels found to put in legend，不能正常显示 legend，不知哪里出问题，使用环境为 Spyder。

[xider]

没有代码看不出问题

[songdg]

这是书上的一个例子，我发现不用 plt.show()就能显示，但是 plt.legend(loc=(0.64,0.1))就显示上面的提示。
import matplotlib.pyplot as plt

d = [11,12,13,14,15,16,17]

t0 = [15.3,12.6,12.7,13.2,12.3,11.4,12.8]
t1 = [26.1,26.2,24.3,25.1,26.7,27.8,26.9]
t2 = [22.3,20.6,19.8,21.6,21.3,19.4,21.4]

plt.plot(d,t0,label='Tokyo')
plt.plot(d,t1,label='Hawaii')
plt.plot(d,t2,label='Hong Kong')

plt.xlim(11,15)
plt.ylim(0,30)

plt.xlabel('Date',size=12,fontweight='semibold')
plt.ylabel('Temperature (°C)',size=12,fontweight='semibold')

plt.grid(True,linewidth=0.5,color='#aaaaaa',linestyle='-')

plt.title("Daily temperature of 3 cities in the second week of December", size=14, fontweight='bold')

plt.legend(loc=(0.64,0.1))
plt.show()