a1g3.py

from keras.applications.vgg16 import VGG16
from keras.layers import GlobalAveragePooling2D, Flatten, Dense, Input, Dropout
from keras.models import Model
from keras.optimizers import Adam
from keras import backend as K

# include_top=False to remove the last layer
initial_model = VGG16(weights="imagenet", include_top=False, input_tensor = Input(shape=(3,224,224)))
x = Flatten()(initial_model.output)

# we add a Dense layer
x = Dense(batches.nb_class, activation='softmax')(x)

# new model with "frozen" layers (except the last one)
model = Model(initial_model.input, x)
for layer in initial_model.layers: layer.trainable=False

model.compile(optimizer=Adam(lr=0.001),
              loss='categorical_crossentropy', 
              metrics=['accuracy'])