Exploring MNIST with TensorFlow, from the very beginning, to an Android Application

Hi everyone,

I’ve recently started to study TensorFlow, and is such a great framework and TensorBoard is amazing.

But I’m not here to say how much is awesome (you know it), I’m here to talk about some of the things I’ve been doing with TensorFlow.

Basically, the HelloWorld of TensorFlow is to build a model to classify MNIST digits, so I created a repository with a lot of links to cool MNIST tutorials, some more simple and direct, others more complex. And I also created a repository for a handwritten digits classifier on Android and how to build one on your own.


Hope it helps somehow, have a nice day!

Exploring MNIST with TensorFlow, from the very beginning, to an Android Application

About Outreachy

Hi everyone,

I’ll be quick in this post, I’ll just talk a little bit about what changed since the last post about Outreachy.


  1. I finished the implementation ( \o/ yeeey), but the code wasn’t merged yet ( :/ not so yeeey), and this was mainly because of the new stable version (Ocata) that started being created at the end of January, so this means no new feature could be merged, but the frozen time has ended, the winter is not coming, so this means the code should be merged soon.
  2. I’ve blogged a little about Mocking, which was a new concept I had to learn in order to make good unit tests for my patch.
  3. I tested my code manually:
    1. ran Hadoop, Spark and Storm jobs with multiple scenarios fixing some bus
  4. And currently, I’m reviewing code and making other contributions to the community (adding code, tests, fixing bugs)!
About Outreachy

A fast introduction to Mocking with Python

Hey there,

This post goal is to talk a little about Mocking, and how to do that (hopefully well) in Python. These are the main topics of this article, have fun!

  1. Are you mocking me, what is mock?
  2. Mocking use cases
  3. How to mock in Python?
  4. References

Are you mocking me, what is mock?


Mocking is basically to abstract some part of your code (function call, variable, API request, system call, …) and instead of calling the real thing, just pretend that it is there and it works correctly.

Why do you want this?

Mocking is mainly used in unit testing, why do we run unit tests? To be more confident that some particular and well-defined part of you code is working as it should. But what if part A of the code, that you’re interested in testing with unit tests, has a dependency with complex part B, you definitely don’t want the unit test testing the complex part B but mainly the part A, and complex part B will have its own unit tests, right? So how can we abstract complex part B? That’s right, Mocking it!!!

“In short, mocking is creating objects that simulate the behavior of real objects.” [2]

Mocking use cases


There’s a lot of valid use cases for Mocking, all of the ones I’ll say are related to unit tests because it is the mainly general use case for Mocking.

  • As I said in the last section, a good reason to mock a part of your code is in order to maintain unit tests isolated and concise. It’s not a good thing to have a unit test that tests a lot of things at once. You’re probably will prefer to break this big unit test in smaller ones, and mock can offer a cool way to do it!
  • Sometimes part of the code you want to test is just not working as it should (not ready yet, unstable, for some reason not available, failing), mocking in this case, is a good thing, because you can test the already stable part of the code.
  • To actually run some part of the code can be too costly or have some side effect not desired (API requests, create files, writing in files, system calls), so mocking can really help you test the code without worrying with these.
  • Test unpredictable code, good unit tests are always executed expecting the same values, random values can be mocked to avoid randomness in the unit tests.
  • Mock a certain complex object that you don’t really need to have it entirely, you can mock only the parts that interest you in the context.
  • And many more cases….

Important: Mocking is very powerful, but do it “the right way” is not that simple and involves practice and experience, a lot Mocking (especially bad mocking) can actually make your unit tests less effective.

How to mock in Python?

> Using the mock package [5].

Whatcan you do with the mock package?


  • Pretend to be anything you want!
import mock

anything = mock.Mock(return_value=3)
print anything() # 3

“Mock is a flexible mock object intended to replace the use of stubs and test doubles throughout your code”. The Mock Class can be used to repeat basically anything in the code, in the example above it represents s function that returns 3. Other useful things you can define for the Mock objects are:

  • “side_effect: A function to be called whenever the Mock is called. See theside_effect attribute. Useful for raising exceptions or dynamically changing return values. If side_effect is an iterable then each call to the mock will return the next value from the iterable.”

  • “return_value: The value returned when the mock is called. By default this is a new Mock (created on first access). “

  • “name: If the mock has a name then it will be used in the repr of the mock. This can be useful for debugging. The name is propagated to child mocks.”

An alternative for Mock Class is MagicMock, “MagicMock is a subclass of Mock with default implementations of most of the magic methods. You can use MagicMock without having to configure the magic methods yourself.”

  • Pretend to be a particular thing (object, function, call, …)
from mock import create_autospec

def any_function(a, b, c):

mock_function = create_autospec(any_function, return_value='unicorn')
print mock_function(1, 2, 3)
# returns 'unicorn'
mock_function.assert_called_once_with(1, 2, 3)
print mock_function('wrong arguments')
# error

“The mock.create_autospec method creates a functionally equivalent instance to the provided class. What this means, practically speaking, is that when the returned instance is interacted with, it will raise exceptions if used in illegal ways.”

from mock import patch

class SomeClass(object):
 def __init__(self):

def function(mock_class):
 return mock_class is SomeClass

print function()

patch() as function decorator, creating the mock for you and passing it into the decorated function”. patch() will replace the class (or method) by a magicMock




[1] https://www.toptal.com/python/an-introduction-to-mocking-in-python

[2] http://stackoverflow.com/questions/2665812/what-is-mocking

[3] http://www.voidspace.org.uk/python/mock/mock.html

[4] https://docs.python.org/3/library/unittest.mock.html

[5] http://blog.thedigitalcatonline.com/blog/2016/03/06/python-mocks-a-gentle-introduction-part-1/#.WH9emXUrKkB




A fast introduction to Mocking with Python

Hey, How is Outreachy going?

Hey there!

First of all sorry for the absent time without writing on the blog (especially not writing about Outreachy), but anyway… Happy 2017, and we’re back on track!

So, the last Outreachy post was about how to run a MapReduce job using DevStack and different types of data sources as input and output. In this article, I’m gonna talk a little about the things I’ve done until now in this internship and what I’m currently doing.

As I said before,  my internship project is to refactor some data source/job binary related code in order to create a clean abstraction that will allow new developers to implement new data source types and job binary types more easily. So, how are things until now?

  1. My first task was to learn a little more about stevedore and how Sahara uses it
  2. Then I’ve set up the DevStack environment in order to run MapReduce jobs and to learn how to do that with multiple types of data source (just in order to understand how the final user does it)
  3. One of the major tasks I had to do was to create the abstraction itself, it demanded a lot of coding reading and grepping code all over the Sahara repository. The result of this task was the creation of the spec and blueprint of the project. These are still being improved accordingly with task 4.
  4. Develop the abstraction and the data source/job binary types implementation, and of course, refactor the code in order to adapt for these abstractions. This is what I’m currently working on and the code can be seen here.

I hope this post was helpful somehow, and have a nice day!

Hey, How is Outreachy going?

Women Who Reign: Marianne Linhares



“It takes a great deal of courage to stand up to your enemies, but even more to stand up to your friends.” — J.K. Rowling

Tell us about yourself along with a fun fact!
Hey everyone, my name is Marianne Linhares, I’m from Brazil and I’m a Computer Science undergraduate student at the Universidade Federal de Campina Grande and currently a fellow coach at the Paraíba State Olympiad in Informatics.

Things I’m passionate about: my friends and family, education, math, music, code, pizza, video games, this video, and helping people (in no particular order, but pizza first haha).
Things I just don’t tolerate: prejudice, ignorance, a closed mind and a closed heart.

Fun fact about me: I’ve played the electric guitar since I was 11 years old. At that time I specifically wanted to learn to play the electric guitar instead of acoustic guitar because I was really into…

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Women Who Reign: Marianne Linhares

URI – Warm up Contest to OBI 2016 -second phase

Hey there,

Not so recently happened the Warm up Contest to OBI 2016 and I was one of the authors again (I was one of the authors in the first phase as well)!

I wrote 1 problem: Rio 2016
I’ll make a fast editorial of this problem and, hopefully, this will help someone :)!

Rio 2016

By: Marianne Linhares

This problem is very up forward, reading the problem carefully is easy to see that we should calculate the distance between the points and then compare it with the time that the match will begin.

Buuuut, be careful with the use of integers, the multiplication may not fit in an integer, so you should use long long int (C++) for the position variables.

A C++ solution can be seen here.

  • Complexity: O(n).
URI – Warm up Contest to OBI 2016 -second phase

My first Chrome Extension – SpotifYoutube


Stop the world, there’s something very weeeird happening… after a couple of very busy months I’ve got the time to start (and finish, I know I’m as shocked as you guys) my first chrome extension.

It’s a simple extension that adds a button to YouTube to search the youtube video title you’re watching in Spotify. I’m very proud of this, it’s working properly and youtube is love, spotify is love, this extension could not be different!


Hope you guys enjoy it!

Source code, Chrome Web Store!


My first Chrome Extension – SpotifYoutube