InvalidArgumentError: You must feed a value for placeholder tensor 'Placeholder_56' with dtype float

Question

I am a newbie in Tensorflow and trying out the code on linear Regression given below:

import tensorflow as tf
import numpy as np
import pandas as pd
from sklearn.datasets import load_boston
import matplotlib.pyplot as plt

boston=load_boston()
type(boston)
boston.feature_names

bd=pd.DataFrame(data=boston.data,columns=boston.feature_names)

bd['Price']=pd.DataFrame(data=boston.target)
np.random.shuffle(bd.values)


W=tf.Variable(0.0)
b=tf.Variable(0.0)
#print(bd.shape[1])

tf.summary.histogram('Weights', W)
tf.summary.histogram('Biases', b)



dataset_input=bd.iloc[:, 0 : bd.shape[1]-1];
#dataset_input.head(2)

dataset_output=bd.iloc[:, bd.shape[1]-1]
dataset_output=dataset_output.values
dataset_output=dataset_output.reshape((bd.shape[0],1)) #converted (506,) to (506,1) because in pandas 
    #the shape was not changing and it was needed later in feed_dict


dataset_input=dataset_input.values  #only dataset_input is in DataFrame form and converting it into np.ndarray


X=tf.placeholder(tf.float32, shape=(None,bd.shape[1]-1))
Y=tf.placeholder(tf.float32, shape=(None,1))

Y_=W*X+b

print(X.shape)
print(Y.shape)


loss=tf.reduce_mean(tf.square(Y_-Y))
tf.summary.scalar('loss',loss)

optimizer=tf.train.GradientDescentOptimizer(0.5)
train=optimizer.minimize(loss)

init=tf.global_variables_initializer()#tf.global_variables_initializer()#tf.initialize_all_variables()
sess=tf.Session()
sess.run(init)



wb_=[]
with tf.Session() as sess:
        summary_merge = tf.summary.merge_all()

        writer=tf.summary.FileWriter("Users/ajay/Documents",sess.graph)

        epochs=10
        sess.run(init)

        for i in range(epochs):
            s_mer=sess.run(summary_merge,feed_dict={X:dataset_input,Y:dataset_output})  #ERROR________ERROR
            sess.run(train,feed_dict={X:dataset_input,Y:dataset_output})

            sess.run(loss)
            writer.add_summary(s_mer,i)

            #tf.summary.histogram(name="loss",values=loss)
            if(i%5==0):
                print(i, sess.run([W,b])) 
                wb_.append(sess.run([W,b]))

print(writer.get_logdir())
print(writer.close())

As the loop runs the line :

 s_mer=sess.run(summary_merge,feed_dict={X:dataset_input,Y:dataset_output})

is giving me error.

I really don't understand why feed_dict is present inside the above line. What would happen if it is not there ?

Also, why are we passing s_mer into add_summary() ? I didn't understand its role. Can't we just pass "summary_merge" into the add_summary().

Please, explain the role of add_summary().

The error I'm getting in my IPython NB is :

InvalidArgumentError                      Traceback (most recent call last)
~/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tensorflow/python/client/session.py in _do_call(self, fn, *args)
   1038     try:
-> 1039       return fn(*args)
   1040     except errors.OpError as e:

~/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tensorflow/python/client/session.py in _run_fn(session, feed_dict, fetch_list, target_list, options, run_metadata)
   1020                                  feed_dict, fetch_list, target_list,
-> 1021                                  status, run_metadata)
   1022 

~/anaconda3/envs/Tensorflow/lib/python3.6/contextlib.py in __exit__(self, type, value, traceback)
     87             try:
---> 88                 next(self.gen)
     89             except StopIteration:

~/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tensorflow/python/framework/errors_impl.py in raise_exception_on_not_ok_status()
    465           compat.as_text(pywrap_tensorflow.TF_Message(status)),
--> 466           pywrap_tensorflow.TF_GetCode(status))
    467   finally:

InvalidArgumentError: You must feed a value for placeholder tensor 'Placeholder_56' with dtype float
     [[Node: Placeholder_56 = Placeholder[dtype=DT_FLOAT, shape=[], _device="/job:localhost/replica:0/task:0/cpu:0"]()]]

During handling of the above exception, another exception occurred:

InvalidArgumentError                      Traceback (most recent call last)
<ipython-input-48-ca71ed6cdb0f> in <module>()
     68 
     69     for i in range(epochs):
---> 70         s_mer=sess.run(summary_merge,feed_dict={X:dataset_input,Y:dataset_output})  #ERROR________ERROR
     71         sess.run(train,feed_dict={X:dataset_input,Y:dataset_output})
     72 

~/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tensorflow/python/client/session.py in run(self, fetches, feed_dict, options, run_metadata)
    776     try:
    777       result = self._run(None, fetches, feed_dict, options_ptr,
--> 778                          run_metadata_ptr)
    779       if run_metadata:
    780         proto_data = tf_session.TF_GetBuffer(run_metadata_ptr)

~/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tensorflow/python/client/session.py in _run(self, handle, fetches, feed_dict, options, run_metadata)
    980     if final_fetches or final_targets:
    981       results = self._do_run(handle, final_targets, final_fetches,
--> 982                              feed_dict_string, options, run_metadata)
    983     else:
    984       results = []

~/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tensorflow/python/client/session.py in _do_run(self, handle, target_list, fetch_list, feed_dict, options, run_metadata)
   1030     if handle is None:
   1031       return self._do_call(_run_fn, self._session, feed_dict, fetch_list,
-> 1032                            target_list, options, run_metadata)
   1033     else:
   1034       return self._do_call(_prun_fn, self._session, handle, feed_dict,

~/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tensorflow/python/client/session.py in _do_call(self, fn, *args)
   1050         except KeyError:
   1051           pass
-> 1052       raise type(e)(node_def, op, message)
   1053 
   1054   def _extend_graph(self):

InvalidArgumentError: You must feed a value for placeholder tensor 'Placeholder_56' with dtype float
     [[Node: Placeholder_56 = Placeholder[dtype=DT_FLOAT, shape=[], _device="/job:localhost/replica:0/task:0/cpu:0"]()]]

Caused by op 'Placeholder_56', defined at:
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/ipykernel_launcher.py", line 16, in <module>
    app.launch_new_instance()
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/traitlets/config/application.py", line 658, in launch_instance
    app.start()
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/ipykernel/kernelapp.py", line 486, in start
    self.io_loop.start()
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tornado/platform/asyncio.py", line 127, in start
    self.asyncio_loop.run_forever()
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/asyncio/base_events.py", line 421, in run_forever
    self._run_once()
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/asyncio/base_events.py", line 1431, in _run_once
    handle._run()
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/asyncio/events.py", line 145, in _run
    self._callback(*self._args)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tornado/platform/asyncio.py", line 117, in _handle_events
    handler_func(fileobj, events)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tornado/stack_context.py", line 276, in null_wrapper
    return fn(*args, **kwargs)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/zmq/eventloop/zmqstream.py", line 450, in _handle_events
    self._handle_recv()
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/zmq/eventloop/zmqstream.py", line 480, in _handle_recv
    self._run_callback(callback, msg)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/zmq/eventloop/zmqstream.py", line 432, in _run_callback
    callback(*args, **kwargs)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tornado/stack_context.py", line 276, in null_wrapper
    return fn(*args, **kwargs)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/ipykernel/kernelbase.py", line 283, in dispatcher
    return self.dispatch_shell(stream, msg)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/ipykernel/kernelbase.py", line 233, in dispatch_shell
    handler(stream, idents, msg)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/ipykernel/kernelbase.py", line 399, in execute_request
    user_expressions, allow_stdin)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/ipykernel/ipkernel.py", line 208, in do_execute
    res = shell.run_cell(code, store_history=store_history, silent=silent)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/ipykernel/zmqshell.py", line 537, in run_cell
    return super(ZMQInteractiveShell, self).run_cell(*args, **kwargs)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/IPython/core/interactiveshell.py", line 2662, in run_cell
    raw_cell, store_history, silent, shell_futures)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/IPython/core/interactiveshell.py", line 2785, in _run_cell
    interactivity=interactivity, compiler=compiler, result=result)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/IPython/core/interactiveshell.py", line 2903, in run_ast_nodes
    if self.run_code(code, result):
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/IPython/core/interactiveshell.py", line 2963, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-35-a13d7623267d>", line 47, in <module>
    X=tf.placeholder(tf.float32, shape=(None,bd.shape[1]-1))
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tensorflow/python/ops/array_ops.py", line 1507, in placeholder
    name=name)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tensorflow/python/ops/gen_array_ops.py", line 1997, in _placeholder
    name=name)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tensorflow/python/framework/op_def_library.py", line 768, in apply_op
    op_def=op_def)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tensorflow/python/framework/ops.py", line 2336, in create_op
    original_op=self._default_original_op, op_def=op_def)
  File "/Users/ajay/anaconda3/envs/Tensorflow/lib/python3.6/site-packages/tensorflow/python/framework/ops.py", line 1228, in __init__
    self._traceback = _extract_stack()

InvalidArgumentError (see above for traceback): You must feed a value for placeholder tensor 'Placeholder_56' with dtype float
     [[Node: Placeholder_56 = Placeholder[dtype=DT_FLOAT, shape=[], _device="/job:localhost/replica:0/task:0/cpu:0"]()]]

Answer 1

The problem is that variables dataset_input and dataset_output are of dtype float64 but you use for placeholders float32, but they need to be same. dataset_input = np.array(dataset_input, dtype=np.float32) and dataset_output = np.array(dataset_output, dtype=np.float32) helps on my computer.

Then when you are calling sess.run(loss) you need to add feed_dict={X:dataset_input,Y:dataset_output} as well because it uses X and Y placeholders.

I really don't understand why feed_dict is present inside the above line. What would happen if it is not there ?

You need to use feed_dict to feed data to your placeholders. If you don't provide it with any data then similar errors occurs, because it has no data for your computations.

Hope it helps.