keras中的fit_generator和fit函数均返回History对象，那么History怎么用呢？事实上History对象已经记录了运行输出。在了解之前，我们甚至自己定义回调函数记录损失和准确率等。

相关keras源码位于网址：

class History(Callback): """Callback that records events into a `History` object. This callback is automatically applied to every Keras model. The `History` object gets returned by the `fit` method of models. """ def on_train_begin(self, logs=None): self.epoch = [] self.history = {} def on_epoch_end(self, epoch, logs=None): logs = logs or {} self.epoch.append(epoch) for k, v in logs.items(): self.history.setdefault(k, []).append(v)

可以看出History类对象包含两个属性，分别为epoch和history，epoch为训练轮数。

根据compile参数metrics，history包含不同的内容。比如，当某一次metrics=['accuracy']时，运行如下部分代码我们可以看出，history字典类型，包含val_loss,val_acc,loss,acc四个key值。

####省略若干history = model.fit_generator( mp.train_flow, steps_per_epoch=32, epochs=3, validation_data=mp.test_flow, validation_steps=32)print(history.history)print(history.epoch)print(history.history['val_loss'])

{‘val_loss': [0.4231100323200226, 0.3713115310668945, 0.3836631367206573], ‘val_acc': [0.815, 0.84, 0.83], ‘loss': [0.8348453622311354, 0.5010451343324449, 0.4296100065112114], ‘acc': [0.630859375, 0.7509920634920635, 0.783203125]}
[0, 1, 2]
[0.4231100323200226, 0.3713115310668945, 0.3836631367206573]

补充知识：在ipython中使用%history快速查找历史命令

1、输出所有历史记录，且带有序号

%history -n 150: %cpaste 151: %cpaste 152: print(r">>>>>>>>>") 153: print(r'>>>>>>>>>') 154: print(r'>>>>>>>>><') 155: print(r'>') 156: print(r'>>') 157: print(r'>>>') ...

2、按序号，查找某些序号区间的历史纪录

%history -n 168-170 178 185-190 168: planets 169:for method, group in planets.groupby('method'): print(f'{method:30s} method={group}') 170:for method, group in planets.groupby('method'): print(f'{method:30s} method={group.shape}') 178: %history? 185: %history -u 186: %history -n -u 187: ?%history 188: %history -g method 189: %history -g method print 190: %history -g for method,

3、模糊查找

%history -g print*metho* 120:for method, group in planets.groupby('method'): print(f"{method:30s} shape={groupe.shape}") 121:for method, group in planets.groupby('method'): print(f"{method:30s} shape={group.shape}") 169:for method, group in planets.groupby('method'): print(f'{method:30s} method={group}') 170:for method, group in planets.groupby('method'): print(f'{method:30s} method={group.shape}') 182:for method, group in planets.groupby('method'): print(f"{method:30s shape=group.shape}") 198: %history -g print*metho*

以上这篇keras中的History对象用法就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持。