Python 2 verses Python 3
========================

Much of the example code you'll find online is Python2, rather than Python3

For the most part, they are the same -- so you can sue those examples to learn from.

There are a lot of subtle differences that you don't need to concern yourself with just yet.

But a couple that you'll need to know right off the bat:

print()
-------

In python2, ``print`` is a "statement", rather than a function. That means it didn't require parenthes around what you want printed::

  print something, something_else

This made it a bit less flexible and powerful.

But -- if you try to use it that way in Python3, you'll get an error::

  In [15]: print "this"
    File "<ipython-input-15-70c8add5d16e>", line 1
      print "this"
                 ^
  SyntaxError: Missing parentheses in call to 'print'

So -- if you get this error, simply add the parentheses::

  In [16]: print ("this")
  this

.. nextslide:: division

In python 3, the divsion operator is "smart" when you divide integers::

  In [17]: 1 / 2
  Out[17]: 0.5

However in python2, integer division, will give you an integer result::

  In [1]: 1/2
  Out[1]: 0

In both versions, you can get "integer division" if you want it with a double slash::

  In [1]: 1//2
  Out[1]: 0

And in python2, you can get the behavior of py3 with "true division"::

  In [2]: from __future__ import division

  In [3]: 1/2
  Out[3]: 0.5

For the most part, you just need to be a bit careful with the rare cases where py2 code counts on integer division.


Other py2/py3 differences
-------------------------

Most of the other differences are essentially of implementation details, like getting iterators instead of sequences -- we'll talk about that more when it comes up in class.

There are also a few syntax differences with more advances topics: Exceptions, super(), etc.

We'll talk about all that when we cover those topics.