Below is a minimal test case in which I create a variable `v`

which I want to initialize to a value of 777 (for the simplified test case).

Note: I can't initialize `v`

with a normal initializer because it depends on a normalization constant computed across all variables (some of which aren't yet created at the time `v`

is created).

My solution (below) is to create a boolean variable `full_init_cond`

that I set to True once I've run some initialization/assign OPs once and use `tf.cond`

to ensure they only run the one time.

```
import tensorflow as tf
v = tf.Variable(0, trainable=False)
full_init_cond = tf.Variable(False, trainable=False, dtype=tf.bool)
with tf.control_dependencies([v]):
tf.cond(
full_init_cond,
true_fn=lambda: [tf.no_op],
false_fn=lambda: [tf.assign(v, 777), tf.assign(full_init_cond, True)]
)
```

I'm receiving the following error on the `tf.cond`

line:

```
TypeError: Failed to convert object of type <class 'function'> to Tensor. Contents: <function no_op at 0x7f39abf51400>. Consider casting elements to a supported type.
```

I'm not making much sense of this error.

Update:

To my surprise this simple test seems to produce a valid tensor:

```
tf.cond(full_init_cond, tf.no_op, tf.no_op)
```

Thought this one fails:

```
tf.cond(full_init_cond, lambda: tf.no_op, lambda: tf.no_op)
```

My confusion continues... Tensorflow version 1.5 by the way.

pythontensorflow answered 6 months ago David Parks #1

It turns out that it didn't like the `tf.no_op`

statement.

`tf.cond`

requires that you return the same number and type of operations for either true|false conditions. So instead of `tf.no_op`

I've replaced it with the `tf.identity`

operation as an appropriate stand-in for no_op:

```
import tensorflow as tf
v = tf.Variable(0, trainable=False)
full_init_cond = tf.Variable(False, trainable=False, dtype=tf.bool)
with tf.control_dependencies([v]):
x = tf.cond(
full_init_cond,
true_fn=lambda: [tf.identity(v), tf.identity(full_init_cond)],
false_fn=lambda: [tf.assign(v, 777), tf.assign(full_init_cond, True)]
)
print(x)
```