Written by Links, lotsa links
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What is DIGITAL LIFE doing to YOUR BRAIN?!
This is not an article about genetic algorithms. It’s about us. You, me, that guy over the other side of the coffee shop hunched over his ipad.
Let me explain. This afternoon I attended a meeting with my new clients. After the meeting, I was one of the only people in the room with a camera (on my ipad). So, the project manager running the meeting asked me to photograph the whiteboard and send her a copy.
So, I clicked a couple of shots, checked that they where not washed out with glare or bad contrast and headed back to the office.
When there, I tried to send the picture to the project manager, but the office guest wifi was not working so the email would not send.
There I sat, thinking furiously, “how can I get this photograph over to Eileen? Hmmm. She is sitting over there on her laptop, but I don’t have a wifi connection!’. There I sat for all of 10 seconds until the forehead slapping moment came. I stood up, walked over and handed her my ipad with the picture displayed.
So, I ask, what is living in a digital world doing to our brains when digital problems overshadow analogue solutions?
PvR #004 – Static methods.
In all my previous PvRs I have detailed the Ruby side first. So I thought it only fair that I switch.
Python static methods SUCK.
That’s it, all you need to know. You want more? Details you say? Reasoned argument? Ok.
They REALLY SUCK.
Ok, ok, the devil is in the details and a disclaimer. I don’t claim to be a major authority, I can be wrong. I AM wrong oh, at least 10-15 times a day! If you ask my wife it’s more. So, details :-
You can define static methods with a decorator
class MyClass(object):
@staticmethod
def static_method():
print "We are in the static method called 'static_method'"
Notice the empty brackets defining no formal parameters.
Python uses an explicit ‘self’ parameter included in the formal parameters for methods to identify the current instance. With no implicit ‘self’, static methods don’t have a ‘handle’ on the class. This makes some things really difficult/impossible.
Now, in Ruby, things are a little more civilised.
class MyClass
def self.static_method
puts "We are in the static method called 'static_method'"
end
end
Now, if we create a subclass of MyClass, because there is an explicit self, we have less issues.
class MySubClass
def self.static_method
super
print "We are in the static method of the subclass now"
end
end
And yes, I know, in the Python example all we need to do is call the parent class directly.
class MySubClass(MyClass):
@staticmethod
def static_method():
MyClass.static_method()
print "We are in the static method of the subclass now"
But if we do, we are mentioning the parent class in two places. So, if we refactor it, and change the parent class we have to change it in two places, not just one. AND, there will be no error if I forget.
PvR #003 – methods and properties.
In Ruby, you don’t have access to the properties of an object, not directly anyway. You have to access them via a method.
>> class Klass
>> def initialize
>> @pickled = true
>> end
>>
?> def pickled
>> @pickled
>> end
>>
?> def pickled= value
>> @pickled = value
>> end
>> end
=> nil
>>
?> a = Klass.new
=> #
>> a.pickled
=> nil
>> a.pickled = "Sausage"
=> "Sausage"
>> a.pickled
=> "Sausage"
Thats a little long winded, so ruby offers us some sugar.
>> class Klass1
>> attr_accessor :pickled
>>
?> def initialize
>> @pickled = true
>> end
>> end
Personally, I don’t like either of the above. The assignment within the initialize method is not going through the accessor.
So any logic we place in there to safeguard things is not being performed on the initial assignment
>> class Klass1
>> attr_accessor :pickled
>>
?> def initialize
>> self.pickled = true
>> end
>> end
Much better. So, ruby keeps attributes internal to its objects and forces us to expose what we want. Python is different, idiomatic python tells us accessing properties from outside is fine.
>>> class Klass(object):
... def __init__(self):
... self.pickled = False
...
>>> a = Klass()
>>> a.pickled
False
>>> a.pickled = "Bacon"
>>> a.pickled
'Bacon'
It’s not the same, not at all. There is no place there for guarding things. You CAN guard things though, lets see how you do that.
class Klass(object):
def __init__(self):
self.pickled = True
def _set_pickled(self, new_value):
print "> in setter"
self._pickled = new_value
def _get_pickled(self):
print "> in getter"
return self._pickled
pickled = property(_get_pickled, _set_pickled)
a = Klass()
print a.pickled
a.pickled = False
print a.pickled
a.pickled = "Eggs"
print a.pickled
And there are no prizes for guessing why it is idiomatic to go to the properties directly.
What are these underscores for? Well, by convention any methods you define that are used as the mechanics for how a class operates are ‘guarded’ by adding either one or two underscores.
Another aspect of this is that there are two ‘things’ that you can access on an object, its properties and its methods. Haha, see what I did there? I lied. There is only one. Properties! methods are properties of their objects.
>>> class Klass(object):
... def method(self):
... print "Bingo"
...
>>> a = Klass()
>>> a.method
<bound method Klass.method of <__main__.Klass object at 0x1034198d0>>
>>> a.method()
Bingo
Thats actually quite nice in some ways, it means you can pass around a method on an object to anything that wants a callback. On others its a pain, cos it means that for a lot of things you have to KNOW whether something is a property or a method returning a value. In Ruby, you don’t have that. It is possible to use property() to hide things behind methods or indeed to use the @property decorator to do similar for getters, but it’s a fair bit more cumbersome.
PvR #002 – What am I saying?
Preparing the previous post, I was reminded of something. Something interesting.
In Python, lines of code are statements. But, in Ruby, lines of code are expressions.
This was brought back to me when I started doing the Ruby side, I typed something like :-
>> if 0
>> print "Zero is true"
>> else
?> print "Zero is false"
>> end
Zero is true=> nil
“Zero is code=> nil” wassat?
Well, it turns out that as well as ‘if’ being a statement, it is also an expression, that has a value.
Its value is the value of the code in the executed ‘branch’. Whats that? PRINT has a value of nil? YUP.
So, to make it a little cleaner, I changed it.
>> if 0
>> "Zero is true"
>> else
?> "Zero is false"
>> end
=> "Zero is true"
Now, that looks much neater. So, in Ruby, a block(not to be confused with Block, capital B) of code is a list of expressions and the result of that block of code is the result of the last expression evaluated. This also means that Ruby can take advantage of this to get rid of the need for an explicit “return” statement from a function. A function is written to let the value of the last expression (sort of) fall out of the function as its return value.
In Python, we don’t have this. Statements don’t have a value and we need to define explicit ‘return’ values from functions.
PvR #001 – Truth or Beauty?
In Ruby(1.8.7), truth and falsehood are expressed by the literals “true” and “false”.
true has a class of TrueClass and false has a class of FalseClass.
>> a = {}
=> {}
>> if a
>> "Empty hash is true"
>> else
?> "Empty hash is false"
>> end
=> "Empty hash is true"
>>
>> a = ""
=> ""
>> if a
>> "Empty string is true"
>> else
?> "Empty string is false"
>> end
=> "Empty string is true"
>>
>> a = []
=> []
>> if a
>> "Empty array is true"
>> else
?> "Empty array is false"
>> end
=> "Empty array is true"
>>
>> a = 0
=> 0
>> if a
>> "Zero is true"
>> else
?> "Zero is false"
>> end
=> "Zero is true"
>> if nil
>> "Nil is true"
>> else
?> "Nil is false"
>> end
=> "Nil is false"
That shows some interesting things. Most of the above, I am willing to accept. Empty strings, empty arrays, fine, they can be true, but ZERO? how can zero be true?
Python has a slightly different take on it.
In Python, both of the literal truth values (True and False) are of class bool. Testing the same things as with Ruby gives us :-
>>> if {}:
... print "Empty hash is true"
... else:
... print "Empty hash is false"
...
Empty hash is false
>>> if []:
... print "Empty array is true"
... else:
... print "Empty array is false"
...
Empty array is false
>>> if "":
... print "Empty string is true"
... else:
... print "Empty string is false"
...
Empty string is false
>>> if 0:
... print "Zero is true"
... else:
... print "Zero is false"
...
Zero is false
>>> if None:
... print "None is true"
... else:
... print "None is false"
...
None is false
So, in Python it is possible to use most of the basic objects as truth values but in Ruby, not so much. Personally, I prefer Pythons way with this than Ruby, not least of which is that the two literals are of the same class.
Python vs. Ruby
So, last week, NWRUG and NWPUG had a joint meeting to explore the differences and similarities of the respective languages (Ruby and Python).
In the session we where treated to a basic introduction to both languages, but of necessity, little more than the very basics of each language was covered. Lets face it, how much can you cover in 30-45 minutes?
Anyway, after a quick pint at common and a lively discussion I took my bus home. On the way I thought over what had been covered, what happened and what I went over when I did a training day with the guys at JP74 to compare and contrast rails vs django. I put together a list of rough titles for small snippets of writing going over some of the details that make Python and Ruby fun (but in different ways).
So, it’s a week later and me being me (lord of procrastination, but thats a different story), I still have the list of titles on my ipad and nothing written. So, anyway, I am trying to turn over a new leaf and actually GET to some of the things I SAY I am going to do.
Web chat, websockets and eventmachine
So, I have a little time on my hands at the moment. I’ve started having a play with eventmachine (sort of a ruby nodejs), websockets and webgl (more on webgl later).
Yesterday I started off with a really REALLY simple online webchat. You can see a demo of it here http://fatgeekuk.org/web-chat/.
It leaves MUCH to be desired in both styling and functionality. But, it is a ‘plausible promise’.
Any comments welcome.
Oh god, am I a Sheldon?
In many TV programs you see women talking to each other, and they ask (sometimes obliquely) Which character from “Sex and the City” are YOU, which am I?
Anyway, I am watching “The Big Bang Theory”. I have to wonder if this show is the male geek version of “Sex and the City”. If so, oh god, am *I* a Sheldon?
The new economy, economy 2.0?
Charlie Stross is an incredible writer.
He has written some of my favourite books. One Accelerando (available here) covers the story of a family over three generations. It starts in current day + and ends up 200 or so years in the future.
It is actually a collection of connected short stories. In one, there is a description of ‘Economy 2.0′. The new way for economy to function. In the book, it is physically impossible for humans to participate profitably in e2.0 because they are simply not equiped for it.
I contend that e2.0 has arrived. Algorithmic trading is economy 2.0. Human beings are incapable of participating. I believe strongly that as e2.0 grows (it is already the largest sector in the economy by volume) people will be further marginalised. We will continue in our slide to irrelevance.
Oh happy days.