Type Error When Using Python's Keras for Neural Network

Question

I am trying to use a neural network to predict the price of houses. Here is what the top of the dataset looks like:

    Price   Beds    SqFt    Built   Garage  FullBaths   HalfBaths   LotSqFt
    485000  3       2336    2004    2       2.0          1.0        2178.0
    430000  4       2106    2005    2       2.0          1.0        2178.0
    445000  3       1410    1999    1       2.0          0.0        3049.0

...

Here is how I am coding the neural network (using Python's keras).

dataset = df.values
X = dataset[:,1:8]
Y = dataset[:,0]

from sklearn import preprocessing
from sklearn.model_selection import train_test_split
min_max_scaler = preprocessing.MinMaxScaler()
X_scale = min_max_scaler.fit_transform(X)
X_scale

X_train, X_val_and_test, Y_train, Y_val_and_test = train_test_split(X_scale, Y, test_size=0.3)
X_val, X_test, Y_val, Y_test = train_test_split(X_val_and_test, Y_val_and_test, test_size=0.5)
print(X_train.shape, X_val.shape, X_test.shape, Y_train.shape, Y_val.shape, Y_test.shape)

from keras.models import Sequential
from keras.layers import Dense

model = Sequential(
    Dense(32, activation='relu', input_shape=(7,)),
    Dense(1, activation='relu'))

model.compile(optimizer='sgd',
              loss='mse',
              metrics=['mean_squared_error'])

hist = model.fit(X_train, Y_train,
          batch_size=32, epochs=100,
          validation_data=(X_val, Y_val)) #Error here!

model.evaluate(X_test, Y_test)[1] #Same Error here!

I get the same error when running the hist = line and the model.evaluate line. Here is the error information:

TypeError                                 Traceback (most recent call last)
<ipython-input-19-522714a352ba> in <module>
----> 1 hist = model.fit(X_train, Y_train,
      2           batch_size=32, epochs=100,
      3           validation_data=(X_val, Y_val))

~/opt/anaconda3/lib/python3.8/site-packages/tensorflow/python/keras/engine/training.py in _method_wrapper(self, *args, **kwargs)
    106   def _method_wrapper(self, *args, **kwargs):
    107     if not self._in_multi_worker_mode():  # pylint: disable=protected-access
--> 108       return method(self, *args, **kwargs)
    109 
    110     # Running inside `run_distribute_coordinator` already.

...

TypeError: in user code:

...

name_scope += '/'

    TypeError: unsupported operand type(s) for +=: 'Dense' and 'str'

I'm not sure why this is happening because when I run df.dtypes on my original dataframe, all of the columns are either integers or floats.

Answer 1

Simple fix! You seem to be missing a hard bracket in your model construction. Try using this:

model = Sequential([
    Dense(32, activation='relu', input_shape=(7,)),
    Dense(1, activation='relu'),
])

Hope it helps! Let me know if you have more questions!