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Training Keras model with
"""An example of how to use tf.Dataset in Keras Model"""
import tensorflow as tf # only work from tensorflow==1.9.0-rc1 and after
def training_pipeline():
# #############
# Load Dataset
# #############
(x_train, y_train), (x_test, y_test) = tf.keras.datasets.mnist.load_data()
training_set = tfdata_generator(x_train, y_train, is_training=True, batch_size=_BATCH_SIZE)
testing_set = tfdata_generator(x_test, y_test, is_training=False, batch_size=_BATCH_SIZE)
# #############
# Train Model
# #############
model = keras_model() # your keras model here
model.compile('adam', 'categorical_crossentropy', metrics=['acc'])
steps_per_epoch=len(x_train) // _BATCH_SIZE,
validation_steps=len(x_test) // _BATCH_SIZE,
verbose = 1)
def tfdata_generator(images, labels, is_training, batch_size=128):
'''Construct a data generator using tf.Dataset'''
def preprocess_fn(image, label):
'''A transformation function to preprocess raw data
into trainable input. '''
x = tf.reshape(tf.cast(image, tf.float32), (28, 28, 1))
y = tf.one_hot(tf.cast(label, tf.uint8), _NUM_CLASSES)
return x, y
dataset =, labels))
if is_training:
dataset = dataset.shuffle(1000) # depends on sample size
# Transform and batch data at the same time
dataset = dataset.apply(
preprocess_fn, batch_size,
num_parallel_batches=4, # cpu cores
drop_remainder=True if is_training else False))
dataset = dataset.repeat()
dataset = dataset.prefetch(
return dataset
def keras_model():
from tensorflow.keras.layers import Conv2D, MaxPool2D, Flatten, Dense, Dropout, Input
inputs = Input(shape=(28, 28, 1))
x = Conv2D(32, (3, 3),activation='relu', padding='valid')(inputs)
x = MaxPool2D(pool_size=(2, 2))(x)
x = Conv2D(64, (3, 3), activation='relu')(x)
x = MaxPool2D(pool_size=(2, 2))(x)
x = Flatten()(x)
x = Dense(512, activation='relu')(x)
x = Dropout(0.5)(x)
outputs = Dense(_NUM_CLASSES, activation='softmax')(x)
return tf.keras.Model(inputs, outputs)
if __name__ == '__main__':
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pbamotra commented Jul 17, 2018

Tried reproducing it using
latest tensorflow 1.9 docker image.

File "/usr/local/lib/python2.7/dist-packages/tensorflow/python/keras/_impl/keras/engine/", line 1143, in fit
  File "/usr/local/lib/python2.7/dist-packages/tensorflow/python/keras/_impl/keras/engine/", line 765, in _standardize_user_data
  File "/usr/local/lib/python2.7/dist-packages/tensorflow/python/keras/_impl/keras/engine/", line 150, in standardize_input_data
    data = [standardize_single_array(x) for x in data]
  File "/usr/local/lib/python2.7/dist-packages/tensorflow/python/keras/_impl/keras/engine/", line 88, in standardize_single_array
    elif x.ndim == 1:
AttributeError: 'Iterator' object has no attribute 'ndim'

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datlife commented Jul 20, 2018

Are you using tensorflow > 1.9, @pbamotra?

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nickyua commented Jul 24, 2018

@datlife , I have the same issue. I use tensorflow==1.8.0

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MakiSzz commented Jul 28, 2018

@nickyua , this is not supported until version 1.9. You can refer to this page:

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was84san commented Aug 12, 2018

@nickyua , I have the same error ' AttributeError: 'Iterator' object has no attribute 'ndim' and I used tesnsorflow 1.9. but I am using Keras
as standalone tool with backend of tensor flow. So what do you think guys the problem is?

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dmus commented Aug 13, 2018

Same issue here: AttributeError: 'Iterator' object has no attribute 'ndim'

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datlife commented Aug 27, 2018

Hy guys, please make sure your current tensorflow support tf.Data API for Keras. What is your current tf.__version__ ? It must be greater than 1.9.0.

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Nithanaroy commented Aug 30, 2018

Great snippet. Very precise and complete. Thank you.
What if we do not have x_train in memory but use tf.dataset to read directly a CSV file, how to define steps_per_epoch in

 steps_per_epoch=len(x_train) // _BATCH_SIZE,

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fred-xue commented Sep 19, 2018

@datlife, I'm on 1.10.0. It worked, but the fit() function doc still show fit(x, y, ...), is this handled somewhere else?

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salarjf commented Oct 1, 2018

in training_set.make_one_shot_iterator(), steps_per_epoch=len(x_train) // _BATCH_SIZE, epochs=_EPOCHS, validation_data=testing_set.make_one_shot_iterator(), validation_steps=len(x_test) // _BATCH_SIZE, verbose = 1)
would change if our model had two inputs and one output.

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GladosAI commented Dec 20, 2018

I'am 1.12.0 still have this problem

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soulmachine commented Dec 27, 2018

I'm using make_one_shot_iterator() with model.fit_generator(), tf.__version__== '1.12.0', still got the following error:

TypeError: 'Iterator' object is not an iterator

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XYudong commented Jan 16, 2019

It works for me at tf version 1.12
Thank you so much.

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GPhilo commented Jan 25, 2019

Same error as @was84san but I'm on:


Did anyone manage to solve this error?

Update: The issue seems to come from using keras as a module instead of the tensorflow.keras implementation. Using tensorflow.keras.Model works as expected.

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owenustc commented Feb 20, 2019

I have userd tensorflow.keras.Model, but also meet the error ,which is as follow:
Epoch 1/2
Traceback (most recent call last):
File "", line 176, in
File "/opt/conda/lib/python3.6/site-packages/tensorflow/python/keras/engine/", line 2177, in fit_generator
File "/opt/conda/lib/python3.6/site-packages/tensorflow/python/keras/engine/", line 147, in fit_generator
generator_output = next(output_generator)
File "/opt/conda/lib/python3.6/site-packages/tensorflow/python/keras/utils/", line 831, in get
six.reraise(value.class, value, value.traceback)
File "/opt/conda/lib/python3.6/site-packages/", line 693, in reraise
raise value
TypeError: 'Iterator' object is not an iterator

My code is as follow:
ain the model
net_final.fit_generator(dataset.make_one_shot_iterator(), #train_datagen,
steps_per_epoch = 2, #train_batches.samples // BATCH_SIZE,
validation_data = valid_batches,
validation_steps = valid_batches.samples // BATCH_SIZE,
epochs = 2,

And my versions of keras and tensorflow are 2.1.6 and 1.12.0
from ._conv import register_converters as _register_converters

print (tensorflow.version)
import keras
Using TensorFlow backend.
print (keras.version)

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OrielResearchCure commented May 6, 2019

Hello, sorry if this is not directly related to this code sample. This is the most related post that I could find.
I would appreciate any help / reference.
I am trying to make work with tf.keras using the tf.estimator.
I get an error dimension when I am pushing the train_fn batch to the keras model (after converted it to estimator) . The code looks like that:

`def train_input_fn(batch_size=1):
"""An input function for training"""
print("train_input_fn: start function")

train_dataset =, batch_size=batch_size,label_name='label',
print('train_input_fn: finished make_csv_dataset')
train_dataset =
print("train_input_fn: finished the map with pars_features_vector")
train_dataset = train_dataset.repeat().batch(batch_size)
print("train_input_fn: finished batch size. train_dataset is %s ", train_dataset)
return train_dataset

IMG_SHAPE = (160,160,3)
base_model = tf.keras.applications.MobileNetV2(input_shape=IMG_SHAPE,
include_top = False,
weights = 'imagenet')

base_model.trainable = False

estimator = tf.keras.estimator.model_to_estimator(keras_model = model, model_dir = './date')

#train_input_fn read a CSV of images, resize them and returns dataset batch
train_spec = tf.estimator.TrainSpec(input_fn=train_input_fn, max_steps=20)

#eval_input_fn read a CSV of images, resize them and returns dataset batch of one sample
eval_spec = tf.estimator.EvalSpec(eval_input_fn)

tf.estimator.train_and_evaluate(estimator, train_spec=train_spec, eval_spec=eval_spec)`

the log is:
train_input_fn: finished batch size. train_dataset is %s <BatchDataset shapes: ({mobilenetv2_1.00_160_input: (None, 1, 160, 160, 3)}, (None, 1)), types: ({mobilenetv2_1.00_160_input: tf.float32}, tf.int32)>

and the error is:
ValueError: Input 0 of layer Conv1_pad is incompatible with the layer: expected ndim=4, found ndim=5. Full shape received: [None, 1, 160, 160, 3]

Many thanks for any help,

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off99555 commented Jul 13, 2019

I noticed the delayed training issue and noticed a big speed improvement in tensorflow-gpu-1.13 on my machine when I run tf.enable_eager_execution() before running the code.

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sangyongjia commented Apr 21, 2020

I found tf1.14 still has this issue.
Is there a solution, anyone find it?

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Demetrio92 commented Jun 22, 2020

replace ->
remove .make_one_shot_iterator
and this runs


Python 3.8.3

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