Python printing

[Fourgot]

Mostly just adds parentheses around print statements, making them friendly to both Python 2 and Python 3. Note that while the documentation for print() in Python 2 cites from __future__ import print_function for Python 2.6+, that import and dependency are to assure access to the more robust functionality available with the newer print() function. The older print statement would always ignore an enclosing set of parentheses surrounding its arguments, and for these simple calls should be acceptable in both 2 and 3.

Additional edits are briefly described in the commit message.

[certik]

The idea is correct, but a-a is ugly. Better to use zeros_like:

from numpy import array, zeros_like
b = zeros_like(a)

[certik]

I agree to update the Python source code to the latest Python (3.4). However, I would point out that the older Python 2.7 doesn't ignore the parentheses, unless you import from future (that's probably what you meant):

>>> print("a", "b")
('a', 'b')
>>> from __future__ import print_function
>>> print("a", "b")
a b

[certik]

You should provide a Fortran equivalent as well.

[Fourgot]

I'm unfamiliar with Fortran, which is how I found your page. Is there something you could suggest?

[Fourgot]

the older Python 2.7 doesn't ignore the parentheses

Yeah, it looks like this is a case where the parentheses elicit different behavior between 2 and 3. Python 2 sees a tuple and Python 3 collects the non-keyword arguments and calls str() on them, joining them with the sep argument (defaults to ' ').

You've successfully avoided discussing Python 2 versus 3, which is definitely outside the scope of this document. I suggest abandoning this syntax.

I'll get a commit together shortly.

[certik]

The order is now all mixed up. The point is to show side by side how to do:

1. "Integer", 5, "and float", 5.5, "works fine."
2. "Integer " + str(5) + " and float " + str(5.5) + "."
3. "Integer %d and float %f." % (5, 5.5)

People still use 3) in Python, even in Python 3.4. We can add the format way as well as 4), what corresponds to it is probably the same as the Fortran answer to 3).

But what is most important is to keep the order the same in both Python and Fortran, so that people can quickly learn how to format things in an equivalent way.

[Fourgot]

Yep, totally mixed up now. I'll clean it up again lol

[certik]

I left some more feedback. I am fine with just requiring Python 3.4, and mentioning that you need to do from __future__ import print_function if you use Python 2.7. (In fact, I think that's the way to go, to always assume the latest Python version, which is 3.4, and just provide workarounds for backwards compatibility and keep the workarounds simple.)

[Fourgot]

I am fine with just requiring Python 3.4

Ah, well that makes it all a bit easier, for sure! Great, I'll get some changes to you soon. Thanks for your patience!

[certik]

Excellent. Ping me once you push some patches in, I'll review it again.