tensorflow 的基本运算 加减乘除 placeholder feed_dict配合用法

tensorflow运算的本质

 tensorflow的运算

import tensorflow as tf

a = tf.constant(3)
b = tf.Variable(5)      #常量数据

# 加减乘除操作
myadd = tf.add(a,b)
mysub = tf.subtract(a,b)
mymul = tf.multiply(a,b)
mydi = tf.divide(a,b)

init = tf.global_variables_initializer()
with tf.Session() as sess:
    sess.run(init)
    print("----------------------")
    print("运行结果")
    print(sess.run(myadd))
    print(sess.run(mysub))
    print(sess.run(mymul))
    print(sess.run(mydi))

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运行结果
8
-2
15
0.6

assign，eval()，tf.get_default_session()介绍

import tensorflow as tf

a = tf.constant(3)
b = tf.Variable(5)      #常量数据

# 加减乘除操作
myadd = tf.add(a,b)
mysub = tf.subtract(a,b)
mymul = tf.multiply(a,b)
mydi = tf.divide(a,b)

myassign = tf.assign(b,myadd)

init = tf.global_variables_initializer()
with tf.Session() as sess:
    sess.run(init)
    print("----------------------")
    print("运行结果")
    print(sess.run(myadd))
    print(sess.run(mysub))
    print(sess.run(mymul))
    print(sess.run(mydi))
    print("--------------------------")
    print(sess.run(myassign))
    print(myassign.eval())
    print(tf.get_default_session().run(myassign))

placeholder

import tensorflow as tf

input1 = tf.placeholder(tf.float32)
input2 = tf.placeholder(tf.float32)

output = tf.multiply(input1, input2)

with tf.Session() as sess:
    print("----------------------")
    print("运行结果")
    print(sess.run(output, feed_dict={input1:4, input2:5}))#传入的feed_dict是一个字典值

----------------------
运行结果
20.0