Tensorflow: How to replace a node in a calculation graph?

Question

If you have two disjoint graphs, and want to link them, turning this:

x = tf.placeholder(\'float\')
y = f(x)

y = tf.placeholder(\'float\')
z = f(y)
<         


        

Answer 1

Practical example:

import tensorflow as tf
g1 = tf.Graph()
with g1.as_default():
    # set variables/placeholders
    tf.placeholder(tf.int32, [], name='g1_a')
    tf.placeholder(tf.int32, [], name='g1_b')

    # example on exacting tensor by name
    a = g1.get_tensor_by_name('g1_a:0')
    b = g1.get_tensor_by_name('g1_b:0')

    # operation ==>>     c = 2 * 3 = 6
    mul_op = tf.multiply(a, b, name='g1_mul')
    sess = tf.Session()
    g1_mul_results = sess.run(mul_op, feed_dict={'g1_a:0': 2, 'g1_b:0': 3})
    print('graph1 mul = ', g1_mul_results)  # output = 6

    print('\ngraph01 operations/variables:')
    for op in g1.get_operations():
        print(op.name)

g2 = tf.Graph()
with g2.as_default():
    # set variables/placeholders
    tf.import_graph_def(g1.as_graph_def())
    g2_c = tf.placeholder(tf.int32, [], name='g2_c')

    # example on exacting tensor by name
    g1_b = g2.get_tensor_by_name('import/g1_b:0')
    g1_mul = g2.get_tensor_by_name('import/g1_mul:0')

    # operation ==>>
    b = tf.multiply(g1_b, g2_c, name='g2_var_times_g1_a')
    f = tf.multiply(g1_mul, g1_b, name='g1_mul_times_g1_b')

    print('\ngraph01 operations/variables:')
    for op in g2.get_operations():
        print(op.name)
    sess = tf.Session()

    # graph1 variable 'a' times graph2 variable 'c'(graph2)
    ans = sess.run('g2_var_times_g1_a:0', feed_dict={'g2_c:0': 4, 'import/g1_b:0': 5})
    print('\ngraph2 g2_var_times_g1_a = ', ans)  # output = 20

    # graph1 mul_op (a*b) times graph1 variable 'b'
    ans = sess.run('g1_a_times_g1_b:0',
                   feed_dict={'import/g1_a:0': 6, 'import/g1_b:0': 7})
    print('\ngraph2 g1_mul_times_g1_b:0 = ', ans)  # output = (6*7)*7 = 294

''' output
graph1 mul =  6

graph01 operations/variables:
g1_a
g1_b
g1_mul

graph01 operations/variables:
import/g1_a
import/g1_b
import/g1_mul
g2_c
g2_var_times_g1_a
g1_a_times_g1_b

graph2 g2_var_times_g1_a =  20

graph2 g1_a_times_g1_b:0 =  294
'''

reference LINK