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TensorFlow Scope Decorator
# Working example for my blog post at:
import functools
import tensorflow as tf
from tensorflow.examples.tutorials.mnist import input_data
def doublewrap(function):
A decorator decorator, allowing to use the decorator to be used without
parentheses if no arguments are provided. All arguments must be optional.
def decorator(*args, **kwargs):
if len(args) == 1 and len(kwargs) == 0 and callable(args[0]):
return function(args[0])
return lambda wrapee: function(wrapee, *args, **kwargs)
return decorator
def define_scope(function, scope=None, *args, **kwargs):
A decorator for functions that define TensorFlow operations. The wrapped
function will only be executed once. Subsequent calls to it will directly
return the result so that operations are added to the graph only once.
The operations added by the function live within a tf.variable_scope(). If
this decorator is used with arguments, they will be forwarded to the
variable scope. The scope name defaults to the name of the wrapped
attribute = '_cache_' + function.__name__
name = scope or function.__name__
def decorator(self):
if not hasattr(self, attribute):
with tf.variable_scope(name, *args, **kwargs):
setattr(self, attribute, function(self))
return getattr(self, attribute)
return decorator
class Model:
def __init__(self, image, label):
self.image = image
self.label = label
def prediction(self):
x = self.image
x = tf.contrib.slim.fully_connected(x, 200)
x = tf.contrib.slim.fully_connected(x, 200)
x = tf.contrib.slim.fully_connected(x, 10, tf.nn.softmax)
return x
def optimize(self):
logprob = tf.log(self.prediction + 1e-12)
cross_entropy = -tf.reduce_sum(self.label * logprob)
optimizer = tf.train.RMSPropOptimizer(0.03)
return optimizer.minimize(cross_entropy)
def error(self):
mistakes = tf.not_equal(
tf.argmax(self.label, 1), tf.argmax(self.prediction, 1))
return tf.reduce_mean(tf.cast(mistakes, tf.float32))
def main():
mnist = input_data.read_data_sets('./mnist/', one_hot=True)
image = tf.placeholder(tf.float32, [None, 784])
label = tf.placeholder(tf.float32, [None, 10])
model = Model(image, label)
sess = tf.Session()
for _ in range(10):
images, labels = mnist.test.images, mnist.test.labels
error =, {image: images, label: labels})
print('Test error {:6.2f}%'.format(100 * error))
for _ in range(60):
images, labels = mnist.train.next_batch(100), {image: images, label: labels})
if __name__ == '__main__':

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lfwin commented Jul 15, 2016

I debuged this code and found that:
1 if set breakpoint at line number 15 'setattr(self, attribute, function(self))' which is execute in Model initilization ' model = Model(data, target)' at line number 53, can step in this line, but if set breakpoint before excecution this set attribute line such as line num 52 or line num 25 and can not step into this set attribute line, why?
2 after executing to set attribute self.optimize at line number 25 and befor excuting self.error, self has three attributes, self._optimize, self._error, self._prediction, i don't know how this be generated?


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danijar commented Oct 4, 2016

Hi @lfwin, I don't know why your debugger can't step into setattr() statements. Maybe because it's a built-in function. Regarding your second question, that's the intention of the decorator. Please read my blog post for an explanation, the URL is at the beginning of the file.


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mshvartsman commented Jan 23, 2017

Hi -- is there a license on this code? I'd like to use it in a package that is Apache 2.0 licensed. Happy to have a dependency on it if you prefer to package it up instead.


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rllin commented Jan 26, 2017

Great design! Any idea how it works with tensorflow saver? How would you restore a checkpoint of a session that's baked into this class?


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mihaic commented Jan 27, 2017

@danijar, is it OK to use this code in a project licensed under Apache 2.0?


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pucktada commented Apr 19, 2017

Hi -- will "define_scope" work when the wrapped function have argument others than self? for example, if i try

def prediction(self, batch_size):
and I get "TypeError: prediction() missing 1 required positional argument"


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yuh8 commented May 23, 2017

@pucktada, you may want to redefine "def decorator(self)" to "def decorator(self, *args, **kwargs)". Likewise for function(self, *args, **kwargs) inside the wrapper function


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spk921 commented May 28, 2017

@pucktada Have you solve the problem? @yuh8 how can I redefine it?


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lakshayg commented May 31, 2017

@rllin Have you found a way to use Saver with this model?
@danijar It would we very useful if you can incorporate the ability to save and load trained model using this class. Do you have some ideas on how this can be done?


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tartavull commented Jul 16, 2017

Hey, I tried extending the idea of the decorator here to set the variable names as well


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madvn commented Sep 18, 2017

Thanks for this gist @danijar Could you please explain how the feed_dict in line 87 (or any similar line) works? Are the feed_dict keys same as the args in init ? Thanks.


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madvn commented Sep 18, 2017

I got that part! But I have another question now - Is it possible to define the attributes such as "optimize" in another file that imports this class? If yes, how? Thanks.


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jren2017 commented Oct 4, 2017

Hello, I changed the code a little bit.
I want to change the cost function dynamically in each iteration, the code is here

I want to access the error of last iteration, use the error to calculate the cross-entropy, this sounds weird, but just an example.
Hope you can help have a look.
changed 65th row of the code:
logprob = tf.log(self.prediction + 1e-12) *(1-current_error) #Here changed ????????????


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richdevboston commented Nov 13, 2018

I get the error message below when I run the example. How do I fix it? It appears to be missing the _gru_ops library.
Great article. Thank you.

File "C:\ProgramData\Anaconda3\envs\TensorFlow\lib\site-packages\tensorflow\python\framework\", line 56, in load_op_library
lib_handle = py_tf.TF_LoadLibrary(library_filename)

NotFoundError: C:\ProgramData\Anaconda3\envs\TensorFlow\lib\site-packages\tensorflow\contrib\rnn\python\ not found

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