How can i save tensors object to an numpy array?

Question

I have implemented autoencoder on my custom images data for sign language recognition.Now i want to save tensors object of the output layer to an numpy array. I tried Session.run(tensor) and tensor.eval(). Here is my code.

#define model
x= tf.placeholder(tf.float32,[None,784])
y_=tf.placeholder(tf.float32,[None,6])
k=190
l=180
m=150
n=130
o=100
num_of_epoch=10
w1=tf.Variable(tf.truncated_normal([784,k],stddev=0.1))
b1=tf.Variable(tf.zeros([k]))
w2=tf.Variable(tf.truncated_normal([k,l],stddev=0.1))
b2=tf.Variable(tf.zeros([l]))
w3=tf.Variable(tf.truncated_normal([l,m],stddev=0.1))
b3=tf.Variable(tf.zeros([m]))
w4=tf.Variable(tf.truncated_normal([m,n],stddev=0.1))
b4=tf.Variable(tf.zeros([n]))
w5=tf.Variable(tf.truncated_normal([n,o],stddev=0.1))
b5=tf.Variable(tf.zeros([o]))
w6=tf.Variable(tf.truncated_normal([o,6],stddev=0.1))
b6=tf.Variable(tf.zeros([6]))
y1=tf.nn.relu(tf.matmul(x,w1)+b1)
y2=tf.nn.relu(tf.matmul(y1,w2)+b2)
y3=tf.nn.relu(tf.matmul(y2,w3)+b3)
y4=tf.nn.relu(tf.matmul(y3,w4)+b4)
y5=tf.nn.relu(tf.matmul(y4,w5)+b5)
y=tf.nn.softmax(tf.matmul(y5,w6)+b6)
cross_entropy=tf.reduce_mean(-tf.reduce_sum(y_*tf.log(y),
reduction_indices=[1]))
train_step=tf.train.GradientDescentOptimizer(0.03).minimize(cross_entropy)
init=tf.global_variables_initializer()
with tf.Session() as sess:
    sess.run(init)
    for i in range(num_of_epoch):    
        train_data = {x:x_train,y_:y_train}
        sess.run(train_step,feed_dict=train_data)
    currect_prediction=tf.equal(tf.argmax(y,1),tf.argmax(y_,1))
    accuracy=tf.reduce_mean(tf.cast(currect_prediction,tf.float32))
    sess.run(accuracy,feed_dict={x:x_train,y_:y_train})
    currect_prediction=tf.equal(tf.argmax(y,1),tf.argmax(y_,1))
    accuracy=tf.reduce_mean(tf.cast(currect_prediction,tf.float32))
    sess.run(accuracy,feed_dict=   {x:x_test,y_:y_test})
    y_p = tf.argmax(y, 1).eval() #this line shows me the error
    print(y_p)

I am getting the below error. How can I fix this error and save tensor data to numpy array ?

Traceback (most recent call last):
File "<ipython-input-45-5e38490a3e8e>", line 1, in <module>
runfile('C:/Users/RIFAT/PycharmProjects/tensorflow_autoencoder   
/autoencoderreconstruction.py',
wdir='C:/Users/RIFAT/PycharmProjects/tensorflow_autoencoder')
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\spyder\utils 
\site\sitecustomize.py", line 880, in runfile
execfile(filename, namespace)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\spyder\utils
\site\sitecustomize.py", line 102, in execfile
exec(compile(f.read(), filename, 'exec'), namespace)
File "C:/Users/RIFAT/PycharmProjects/tensorflow_autoencoder
/autoencoderreconstruction.py", line 112, in <module>
y_p = tf.argmax(y, 1).eval()
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tensorflow\python
\framework\ops.py", line 606, in eval
return _eval_using_default_session(self, feed_dict, self.graph, session)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tensorflow\python
\framework\ops.py", line 3928, in _eval_using_default_session
return session.run(tensors, feed_dict)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tensorflow\python\client
\session.py", line 789, in run
run_metadata_ptr)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tensorflow\python\client
\session.py", line 997, in _run
feed_dict_string, options, run_metadata)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tensorflow\python\client
\session.py", line 1132, in _do_run
target_list, options, run_metadata)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tensorflow\python\client
\session.py", line 1152, in _do_call
raise type(e)(node_def, op, message)
InvalidArgumentError: Shape [-1,784] has negative dimensions
[[Node: Placeholder_62 = Placeholder[dtype=DT_FLOAT, shape=[?,784], 
_device="/job:localhost/replica:0/task:0/cpu:0"]()]]
Caused by op 'Placeholder_62', defined at:
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\spyder\utils\ipython
\start_kernel.py", line 231, in <module>
main()
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\spyder\utils\ipython
\start_kernel.py", line 227, in main
kernel.start()
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\ipykernel\kernelapp.py",   
line 477, in start
ioloop.IOLoop.instance().start()
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\zmq\eventloop
\ioloop.py", line 177, in start
super(ZMQIOLoop, self).start()
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tornado\ioloop.py", line   
888, in start
handler_func(fd_obj, events)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tornad
\stack_context.py", line 277, in null_wrapper
return fn(*args, **kwargs)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\zmq\eventloop
\zmqstream.py", line 440, in _handle_events
self._handle_recv()
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\zmq\eventloop
\zmqstream.py", line 472, in _handle_recv
self._run_callback(callback, msg)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\zmq\eventloop
\zmqstream.py", line 414, in _run_callback
callback(*args, **kwargs)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tornado
\stack_context.py", line 277, in null_wrapper
return fn(*args, **kwargs)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\ipykernel
\kernelbase.py", line 283, in dispatcher
return self.dispatch_shell(stream, msg)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\ipykernel
\kernelbase.py", line 235, in dispatch_shell
handler(stream, idents, msg)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\ipykernel
\kernelbase.py", line 399, in execute_request
user_expressions, allow_stdin)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\ipykernel\ipkernel.py",  
line 196, in do_execute
res = shell.run_cell(code, store_history=store_history, silent=silent)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\ipykernel\zmqshell.py", 
line 533, in run_cell
return super(ZMQInteractiveShell, self).run_cell(*args, **kwargs)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\IPython
\core\interactiveshell.py", line 2717, in run_cell
interactivity=interactivity, compiler=compiler, result=result)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\IPython
\core\interactiveshell.py", line 2827, in run_ast_nodes
if self.run_code(code, result):
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\IPython
\core\interactiveshell.py", line 2881, in run_code
exec(code_obj, self.user_global_ns, self.user_ns)
File "<ipython-input-45-5e38490a3e8e>", line 1, in <module>
runfile('C:/Users/RIFAT/PycharmProjects/tensorflow_autoencoder
/autoencoderreconstruction.py', wdir='C:/Users/RIFAT/PycharmProjects
/tensorflow_autoencoder')
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\spyder\utils
\site\sitecustomize.py", line 880, in runfile
execfile(filename, namespace)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\spyder\utils
\site\sitecustomize.py", line 102, in execfile
exec(compile(f.read(), filename, 'exec'), namespace)
File "C:/Users/RIFAT/PycharmProjects/tensorflow_autoencoder
/autoencoderreconstruction.py", line 62, in <module>
x= tf.placeholder(tf.float32,[None,784])
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tensorflow\python
\ops\array_ops.py", line 1530, in placeholder
return gen_array_ops._placeholder(dtype=dtype, shape=shape, name=name)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tensorflow\python
\ops\gen_array_ops.py", line 1954, in _placeholder
name=name)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tensorflow\python
\framework\op_def_library.py", line 767, in apply_op
op_def=op_def)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tensorflow\python  
\framework\ops.py", line 2506, in create_op
original_op=self._default_original_op, op_def=op_def)
File "C:\Users\RIFAT\Anaconda3\lib\site-packages\tensorflow\python
\framework\ops.py", line 1269, in __init__
self._traceback = _extract_stack()
InvalidArgumentError (see above for traceback): Shape [-1,784] has 
negative dimensions
[[Node: Placeholder_62 = Placeholder[dtype=DT_FLOAT, shape=[?,784], 
_device="/job:localhost/replica:0/task:0/cpu:0"]()]]

Answer 1

That's because y is a tensor in the graph and not a variable. When you run .eval() on a variable, it gives you the current value held by that variable in that session but if you run .eval() on a tensor instead like tf.argmax(y, 1).eval() in your case then tensor flow runs the graph to that node to get the value of that node. And since in your case, it doesn't get the value of the placeholder x and y_ while running the graph, it gives the error. One way to resolve this error is by passing the values of the placeholders in your eval call like this:

tf.argmax(y, 1).eval(feed_dict= {x:x_test,y_:y_test})

But, a more preferred way is giving the context of your session to the eval call in which case it will return the value of the tensor. Ex:

tf.argmax(y, 1).eval(session = sess)

Answer 2

Your question is not 100% clear. But the error you are seeing is caused by the fact that you try to run the graph without the feed dict in place. To see the output of the prediction (that is with the argmax(y, 1) present) you'd simply run:

y_p = sess.run(tf.argmax(y, 1), feed_dict=train_data)
print(y_p)

But that will give you the actual predicted value (on the train data as this is fed, to get this on the test data, simply geed in the test_data). To get the probabilities you'd pull y without the argmax:

y_p = sess.run(y, feed_dict=train_data)
print(y_p)