Programming

I know I said, I’d start with the basics, Reuven, but please forgive me this once :) Will do the rest, bottom up :) Have started up with this, because I’m fascinated with how folks manage to build in so much functionality into short, easy to read statements. To my mind, comprehensions are the pithy proverbs of the programming world. So here goes … Notes This style of writing code, comes from functional programming Functional Programming is another style of writing code It assumes that data is immutable. (Or at least it treats it as such) It does not change the originals I work with. (I assume this means that I always work on a copy or something) we work with sequences of data and create new ones based on the old ones (changing case of a sentence, comes to mind) There are a bunch of techniques/patterns/heuristics that’ll let me do that We can treat functions as data and pass them around as arguments to other functions. The functools module assists with writing such code Why code in such a manner? Some benefits include them being easier to read, easier to debug, shorter, more understandable. Distributed Computing / Multiprocessing across processors and cores/threads makes these techniques more relevant in this day and age My personal need is to write easy to read code, like when I see a well crafted list comprehension If I want to square a list of numbers, my current go to is to generate a new list, using a for loop. Comprehensions are a better way of doing this For loops are far when I want to execute something on each item of something iterable, like a list or a dictionary. when i want to have a statement happen If just want to transmute the elements of list into something else, change each element, like square them all above, then comprehensions are my friend Here’s a list comprehension to square a list of numbers from the list numbers. [one_number * one_number for one_number in numbers] The square brackets make it a list comprehension. If I want dictionary comprehensions, I would abut them with curly braces {}. And if I use (), I’ll get a generator expression (which I know only the bare basics about) For loops and comprehensions might look similar, but they really are different Note: whatever expression you use to generate output has to return something. like the square expression above . because what I want to do is catch all my results in a container. functions (like the print function) that return None as their result, cannot work here. They will display stuff, but store only None in our comprehension container :) I can also write the comprehesion over multiple lines (works because they are bounded by the list brackets here or bounded by other brackets elswhere) [one_number * one_number for one_number in numbers] here with the breakdown of the lines, the first line becomes my output generator; the expression I want to use and the second line, the data I want to process. Much more readable this way learning / feedback/ experiences from doing exercises Exercises today required a bit of head scratching and a bit of research, but were relatively simple I should keep in mind that the computer can go crazy too. I kept wondering why my code wouldn’t run and and kept banging my head for an hour. Even Rueven’s solution was what I did. Until I restarted my Jupyter note book and everything worked the way I expected. Should have a time limit on how much struggling I do. From the last week, it looks like I am a real sucker for pain otherwise. Half an hour tops and then go look up the solution. Have reached the second set of exercises and realised why Reuven told me to start with the basics. I failed with the second one in this set. I just know, there is a simple solution and I cannot seem to get it. This basically means … yes … that my foundations are creaky. Note to self, walk before you can run. By Jove, you should’ve learnt that by now! :) So this is me, waving goodbye sorrowfully to comprehensions. Will start with the basic Python course tomorrow. But I’ll be back soon enough, damn it! ...

Done with Reuven Lerner’s OOP basics Notes len does the right thing across multiple types of objects. it counts characters in a string, elements in a list, and key-value pairs in a dictionary. how does it know how to do that? that is because len uses a magic method (methods that have a __ for a prefix and suffix) len uses the __len__ method which i can use in my own classes, to implement a len method for my classes If I choose to do so, I need to realise what those underlying methods expect to return and return the same type in my classes. __len__ expects to return integers, so when I implement it in my classes, I ought not to return a string. Once again Reuven strongly suggests using common sense :) same thing when i try to print something. it calls the magic method __str__ to do stuff. or if i try to do repr to check for raw representations, the __repr__ method is called. Python is filled with these methods which I can use to allow my classes to have standard Python like functionality. like a print(doggie) should give me details about the cute pup object i just created, if I have taken the time and attention to implement the __str__ or __repr__ methods most of these methods come with the base primitive class object which every class inherits from. so i get them for free. and then i can override them and customise them to what I want to show. people try standard methods on new objects. implementing them is much better than creating my own and asking people to use ’em. if both are equal or really similar, ok to just use only __repr__. later when I have experience and other needs, i can implement __str__ too learning / feedback/ experiences from doing exercises Despite warning myself above, I went ahead and made the mistake of returning a whole lovely string, instead of an integer, when I tried to implement the len method on my class XD and then I forgot to add the f prefix to an f-string and wondered why it was not interpolating for nearly 30 mins Reuven has a wry sense of humour. In one of my exercises I get to create classes of animals for a zoo, with various attributes such as colour and legs and so forth. Then he has me put them in cages. After making me put 2 sheep in a cage with a wolf, he wonders if the legs of the sheep ought to be reduced or not XD The number of typos I am making is staggering. Missing colons, missing quotes, missing brackets. If this is Python, I shudder to think how I’d fare if I picked up a static language to learn XD Wasted another half an hour because I spelt colours with capitals like Black and then later looked for black and was tearing my hair out, because I knew there were black animals and why in tarnation, would Python not show me them XD Saw Reuven do nested comprehensions and now I want to do that too! it took him one well thought out line to do what I did in 2 multiline functions Final Words This was amazing! I learnt so much about classes and the way they work. Reuven has a very joyful pedagogy. I love him go hahahaha like Santa Claus. I love the fact that he makes mistakes. I love that for every problem, he poses, he has various approaches. His fluency shines through every lesson. I got lucky with the Pycharm Humble Bundle. But I loved this so much, that I am going to sign up for all the Lerner courses, I possibly can. Beginning with the basics. If OOP is any indicator, the journey is going to be lots of fun. ...

Learnt about Class Attributes and Inheritance, today. Notes The way we write functions/methods and define classes might look similar, class CrazyTalk(object): and def how_now_brown_cow(): The way they behave/execute, though is wildly different. Classes run / spring to life as soon as the program launches. Functions don’t, unless they are called. Realised that objects are containers. What you can do with the object depends on what is in it. Does it hold a dictionary with various methods to modify it? Does it just hold a bunch of text? Reminds me of media formats as containers. A mp4 file is not just an mp4 file. The video resolution could vary from one file to another. The type of audio encoding could be different. It could carry multiple streams of audio or video or other metadata. What you can do with the file or where you can play it, depends on what is inside it. Same with classes and objects. ...

Learnt about methods today. Notes follow … My understanding about methods? They are functions in classes that help me manipulate the data the objects contain when they are created. I have been using something them subconsciously all along. The __init__ method, that is called/run automatically every time an object is created. Aha A nice way to unpack the .notation i use Let’s say I have a class SquareNumbers that has a function (method) ­— x2 — that will, you know, square a number. And then I create an object f with a number and call the square method on it. ...

Did a few exercises today. They were simple. Create a few classes, change them, modify them, use a list as an attribute and so on. In a couple of ways, this was just what I needed. One, I had an extremely busy day at work, and so I did not have the brain power to do anything complex, so I needed the bar really low any way. And two, I’ve realised, that I have always tried to just read a book and then leap mountains. I don’t know why. I must be a sucker for pain. And then when stuff does not work, I sulk and get frustrated. Easing into hard topics like this, makes it more enjoyable for me and I learn better. This is a meta skill, I should remember to use. Come to think of it, everything I have learnt recently, actually learnt, has been this way. I learnt Dvorak and touch typing, slowly, key by single key. I learnt to diet and lose weight, by tens of grammes in the beginning. ...

Notes I’ve taken from the videos I watched, today. This is my attempt at Feynman-ing (below), what I learnt so far. Classes and Object Oriented Programming started to come together for me, when I saw Kushal using them. To use my father’s carpentry analogy, I could in theory just hammer nails into wood to join them. But to make a really strong joint, I could use other methods. I could screw pieces of wood together, which is markedly better than just nailing them. I could chisel wood and create a dovetail or mortise joint. ...