部分內容**
先給乙個例項,
#先導入tensorflow
import tensorflow as tf
# create tensorflow object called hello_constant
hello_constant = tf.constant('hello world!')
with tf.session() as sess:
# run the tf.constant operation in the session
output = sess.run(hello_constant)
print(output)
# tensor1 是乙個0維的 int32 tensor
tensor1 = tf.constant(1234)
# tensor2 是乙個1維的 int32 tensor
tensor2 = tf.constant([123,456,789])
# tensor3 是乙個二維的 int32 tensor
tensor3 = tf.constant([ [123,456,789], [222,333,444] ])
output = sess.run(hello_constant)
x = tf.placeholder(tf.string)
with tf.session() as sess:
output = sess.run(x, feed_dict=)
x = tf.placeholder(tf.string)
y = tf.placeholder(tf.int32)
z = tf.placeholder(tf.float32)
with tf.session() as sess:
output = sess.run(x, feed_dict=)
a = tf.constant(2, tf.int16)
b = tf.constant(4, tf.float32)
graph = tf.graph()
with graph.as_default():
a = tf.variable(8, tf.float32)
b = tf.variable(tf.zeros([2, 2], tf.float32))
with tf.session(graph=graph) as session:
tf.global_variables_initializer().run()
print(session.run(a))
print(session.run(b))
實驗結果:
8
[[ 0. 0.]
[ 0. 0.]]
tensorflow在圖graph中定義了a,b兩個變數,在啟動graph時候,必須把變數載入到記憶體中(通過方法global_variables_initializer())
,這樣才能在session中run(a),run(b)
session只能啟動graph=graph中的變數,如果變數不在graph中就會報錯。
import tensorflow as tf
graph = tf.graph()
with graph.as_default():
a = tf.variable(8, tf.float32)
b = tf.variable(tf.zeros([2, 2], tf.float32))
a = tf.constant(2, tf.int16)
b = tf.constant(4, tf.float32)
with tf.session(graph=graph) as session:
tf.global_variables_initializer().run()
print(session.run(a))
print(session.run(b))
報錯
valueerror: fetch argument 'const:0' shape=() dtype=int16> cannot be interpreted as
a tensor. (tensor tensor("const:0", shape=(), dtype=int16) is not
anelement
of this graph.)
變數必須初始化才會有具體的值global_variables_initializer()進行初始化,而常量就不用初始化。
佔位符
佔位符是定義乙個可變的常量,佔位符賦值後不用初始化就可以獲取值。
import tensorflow as tf
x = tf.placeholder(tf.string)
y = tf.placeholder(tf.int32)
z = tf.placeholder(tf.float32)
with tf.session() as sess:
output = sess.run(x, feed_dict=)
print(output)
實驗結果:
test string
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