当你对train_gen进行第一次赋值时，这是在函数作用域之外的。当你调用函数train_gen时，可能不再定义...
Alonso's engine fails in first practice session for Barcelona GP Fernando Alonso's first practice session ahead of the Spanish Grand Prix in Barcelona ended in disaster as his car suffered an engine problem on Thursday. The myth about China's "chequebook diplomacy" As the popularity of the Bel...