Apple's Feckless Download Protocol

For those of us who live mostly off the grid, with inconsistent WiFi through hosts that flake out frequently, Apple's AppStore download protocol is absolutely infuriating. It's the most brittle damn protocol I've ever seen.

When there's any disruption, it simply discards the data it has and starts again.

How stupid. How blatantly and infuriatingly stupid.

If I pause a download, it will resume. If it breaks, it will not resume. WTF?

For some things, I can use BitTorrent, which tolerates noisy links. But for proper AppStore Apps, their protocol is the pits.

Anyone know anyone at Apple who's able to work on a solution to this?

Secure Salted Password Hashing

An excellent exposition of secure salted password hashing.

https://crackstation.net/hashing-security.htm

This was really quite nice. It didn't have a Python version, but the clarity of the exposition makes the Python easy to write.

A few months back, I had this mystery conversation: http://slott-softwarearchitect.blogspot.com/2012/08/password-encryption-short-answer-dont.html.

While this is not going to produce identical results to the code shown in the blog post, it seems to fit the requirements.

from hashlib import sha256
import os
class Authentication:
    iterations= 1000
    def __init__( self, username, password ):
        """Works with bytes. Not Unicode strings."""
        self.username= username
        self.salt= os.urandom(24)
        self.hash= self._iter_hash( self.iterations, self.salt, username, password )
    @staticmethod
    def _iter_hash( iterations, salt, username, password ):
        seed= salt+b":"+username+b":"+password
        for i in range(iterations):
            seed= sha256( seed ).digest()
        return seed
    def __eq__( self, other ):
        return self.username == other.username and self.hash == other.hash
    def __hash__( self, other ):
        return hash(self.hash)
    def __repr__( self ):
        salt_x= "".join( "{0:x}".format(b) for b in self.salt )
        hash_x= "".join( "{0:x}".format(b) for b in self.hash )
        return "{username} {iterations:d}:{salt}:{hash}".format(
            username=self.username, iterations=self.iterations,
            salt=salt_x, hash=hash_x)
    def match( self, password ):
        test= self._iter_hash( self.iterations, self.salt, self.username, password )
        return self.hash == test # Constant Time is Best

It may be helpful to use __slots__ with this to reduce the storage and make the object less mutable.

Perhaps I didn't google well enough to find a clear explanation that also included Python code samples.

Python vs. R for Data Science

This: Python Displacing R As The Programming Language For Data Science.

Recently, I've had a former colleague asking questions about Data Science. See Obstinate Idiocy.

They -- weirdly -- insisted that the only language that made sense to them was Excel.

My response was a blunt "What?"

The Python vs. R post cited above clarifies that reasons why a programming language is a better choice than a "tool" or "platform".

Mac OS X 10.9 and Python 3.3

Finally upgraded to Python 3.3.3. The ordinary maintenance release fixed the problem with the previous release.

The previously documented patch (http://slott-softwarearchitect.blogspot.com/2013/10/mac-os-x-109-mavericks-crashes-python.html) is no longer required.

Time to start incrementally installing all the various add-on components: docutils, PyYaml, Django, Jinja2, SQLAlchemy, etc.

Also, time to put more focus into rewriting various projects to finally cut the cord with Python2. At this point, there's no longer a reason to be looking backwards.

When to choose Python over Java and vice versa ??: A Very Silly Question

The correct answer is: It Doesn't Matter.

In spite of this.

(A) The question gets asked.

And worse.

(B) It gets answered. And people take their answers seriously. As if there are Profound Differences among programming languages.

Among Turing Complete programming languages there are few Profound Differences.

The pragmatic differences are the relative ease (or pain) of expressing specific algorithms or data structures.

This means that there's no easy, blanket, one-size-fits-all answer to such a silly question.

You can have some code (or data) which is painful in Java and less painful in Python.

But.

You can also find an extension library that makes it much, much less painful.

This, alone, makes the question largely moot.

When it comes to a specific project, the question of the team's skills, the existing infrastructure, and any integration requirements are the driving considerations.

Because of this, an incumbent language has huge advantages.

If you've already got a dozen web sites in Java, there's no good reason to flip-flop between Java and Python.

If you're going to switch from some Java Framework to Django, however, you'd do this is part of a strategic commitment to drop Java and convert to Python.

To read the discussion, see LinkedIn Python Community. http://www.linkedin.com/groupItem?view=&gid=25827&type=member&item=5796513808700682243&qid=8612bee7-76e1-4a35-9c80-c163494191b0&trk=groups_most_popular-0-b-ttl&goback=%2Egmp_25827

Mac OS X 10.9 "Mavericks" Crashes Python -- Patch Available

I upgraded to Mac OS X 10.9 "Mavericks" today.

Python 3.2.4 crashed in odd places. Not all the time. But help() stopped working to give one example.

I upgraded to Python 3.3 (it's about time to do that, anyway.)

It crashed, also. Similar places.

Here's the workaround: http://bugs.python.org/issue18458

There's a script which you can download and run. This will tweak your installations until the next maintenance release of Python.

Whew. That was close.

Now I need to square away setuptools and "easy_install-3.3" all the missing pieces of my 3.2 environment.

Required Reading for everyone who said "If it ain't broke, don't fix it."

http://pythonsweetness.tumblr.com/post/64740079543/how-to-lose-172-222-a-second-for-45-minutes

Here an important lesson.

Code Rot is Real.  It Leads to Subtle and Expensive Bugs.

Claiming that code cleanup is just pointless "gold plating" is the kind of thing that can drive a company out of business.