Python 2.xx VS 3.xx

If you are trying to learn Python, especially for Data Science, you are going to come across a bunch a people (myself included) who have been very hesitant to move from Python 2.xx to Python 3.xx.

The reason?

Not Backwards Compatible

Well, when Python 3 first came out, it was made very clear that it was not backwards compatible. While most of the code remained the same, there were some changes that made programs coded in Python fail. A prime example is Print. In Python 2,

Print ‘Hello World!’

was perfectly acceptable, but in Python 3, it fails and throws up an exception. Python 3 had added the requirement for () with print statements

Print(‘Hello World’)   — Python 3 friendly

Well I have a whole bunch of code sitting on my hard drive I like to refer to, and having to go through it cleaning up all the new changes did not exactly seem like the best use of my time, since I am able to just continue using Python


Python is so great for Data Science because of the community of libraries out there providing the data horsepower we all love. (Pandas, Numpy, SciKit Learn, ect).  Well guess what, the changes to Python 3 made some of these libraries unstable. Strike 2, another reason not to waste my time with this new version.

Moving On

Well, it appears that enough time has passed and some people tell me all the bugs have been worked out with Python 3. While Python 2.7 will be supported til 2020 (those who love it, just keep using it I say), I have decided to try putting Python 3 through it’s paces.

My lessons will be reviewed one by one, with the 2.7 code being tested in a 3.4 environment. I will note any changes that need to made to the code to make it 3.4 compatible and add them to the  lesson. Each lesson that has been reviewed will have the following heading.

*Note: This lesson was written using Python 2.xx. If you are using Python any changes to the code will be annotated under headings: Python


If you love 2, just keep using it. You’ve got 3 more years. By that point, whatever revision of 3 we are on may not even look like the current version. But if you want to look ahead, follow along with me as I update my code. (Note, all the original 2.7 code will remain on my site until the time that it is no longer supported)

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