# How to pass observation from CartPole-v0 to neural network using tensorflow

I am trying to learn about RL by implementing DQN with tensorflow. However, I am really stuck with tensorflow.. I just don't understand it. I think I have found the core of what I understand - I dont understand how I should pass placeholders to the network. When I run the code below I get the following error for the last (sess.run()) line:

Can anyone help me by saying what I am doing wrong (or maybe better - what it is that I dont understand) ?

tensorflow.python.framework.errors_impl.InvalidArgumentError: You must feed a value for placeholder tensor 'obs' with dtype double and shape [4]
[[{{node obs}}]]

import numpy as np
import tensorflow as tf
import keras.models
from keras.models import Sequential
from keras.layers import Activation, Dense
import gym

OBS_SPACE=4
ACTION_SPACE=2

def createNN():
model = Sequential()
for i in range(1,4):