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I want to read and understand the code of some of the basic Machine Learning Models like Linear Regression from Python Scikit-learn Package, but it is too confusing at the start. Can someone tell me from where (which class) to start?
If you know the basics and want to know about the internals (not just using it), than I would start with the sklearn Developer’s Guide.
It explains the idea behind the API, explains some of the util functions that are often found in the code, to e.g. check input, and explains how C/C++ and Cython are used within the source to go for most speed - this was confusing me at the beginning as I thought it was all pure Python and did not know about Cython.
I would suggest you to go through some courses online first, for example there is an Econometrics course on Coursera which is dealing with those concepts
https://www.coursera.org/learn/erasmus-econometrics/home/welcome
while most of the time using a full course to understand a concept feels like an overshoot, but in general it is really worth it. The courses I posted were the ones which helped me through my PhD difficulties, and gave a very good overview on not only the technicalities of the given package, but also the purpose it has to be used for.
I'm working on a basic DBMS as a pet project and planning to prototype in Python.
I figure there's a reason there are only a few Python databases, and my gut agrees that my favorite language will be too slow to act as an honest performing database, but I'm looking forward to using it to learn what I need quickly.
Would someone please contradict me? Is Python as ill-suited right now for this sort of thing as I think?
EDIT 4/16-
I've posted another getting-started-on-this-project type question if anyone is interested.
(Non-Relational) DBMS Design Resource
It's doubtful that anything you create as a pet project is going to turn out to be popular. Presumably you are mostly doing this as a learning experience and for fun.
Given these facts, there's no reason to stop yourself so early just because you think there might be performance problems. Just do it and have fun with it. The idea of a pure Python database will at least be academically interesting to others.
You can always do some performance profiling to find the bottlenecks and use the usual approaches in speeding things up (CPython, Cython, ctypes, etc.)
Don't be so quick to dismiss Python's huge benefits that you get in return for the performance hit. Namely rapid development.
If performance isn't a huge issue there's no reason Python can't do what you need, it certainly has all of the tools to do so. Designing a database certainly isn't a trivial undertaking, of course, but assuming you have the know-how and Python-fu to put in everything you need (of course, being helped by all of us here at SO ;) ) then the basic building blocks are all there.
For reference, there's at least one DBMS written in pure Python that I know of: KirbyBase
I am trying to learn Python and referencing the documentation for the standard Python library from the Python website, and I was wondering if this was really the only library and documentation I will need or is there more? I do not plan to program advanced 3d graphics or anything advanced at the moment.
Edit:
Thanks very much for the responses, they were very useful. My problem is where to start on a script I have been thinking of. I want to write a script that converts images into a web format but I am not completely sure where to begin. Thanks for any more help you can provide.
For the basics, yes, the standard Python library is probably all you'll need. But as you continue programming in Python, eventually you will need some other library for some task -- for instance, I recently needed to generate a tone at a specific, but differing, frequency for an application, and pyAudiere did the job just right.
A lot of the other libraries out there generate their documentation differently from the core Python style -- it's just visually different, the content is the same. Some only have docstrings, and you'll be best off reading them in a console, perhaps.
Regardless of how the other documentation is generated, get used to looking through the Python APIs to find the functions/classes/methods you need. When the time comes for you to use non-core libraries, you'll know what you want to do, but you'll have to find how to do it.
For the future, it wouldn't hurt to be familiar with C, either. There's a number of Python libraries that are actually just wrappers around C libraries, and the documentation for the Python libraries is just the same as the documentation for the C libraries. PyOpenGL comes to mind, but it's been a while since I've personally used it.
As others have said, it depends on what you're into. The package index at http://pypi.python.org/pypi/ has categories and summaries that are helpful in seeing what other libraries are available for different purposes. (Select "Browse packages" on the left to see the categories.)
One very common library, that should also fit your current needs, is the Python Image Library (PIL).
Note: the latest version is still in beta, and available only at Effbot site.
If you're just beginning, all you'll need to know is the stuff you can get from the Python website. Failing that a quick Google is the fastest way to get (most) Python answers these days.
As you develop your skills and become more advanced, you'll start looking for more exciting things to do, at which point you'll naturally start coming across other libraries (for example, pygame) that you can use for your more advanced projects.
It's very hard to answer this without knowing what you're planning on using Python for. I recommend Dive Into Python as a useful resource for learning Python.
In terms of popular third party frameworks, for web applications there's the Django framework and associated documentation, network stuff there's Twisted ... the list goes on. It really depends on what you're hoping to do!
Assuming that the standard library doesn't provide what we need and we don't have the time, or the knowledge, to implement the code we reuse 3rd party libraries.
This is a common attitude regardless of the programming language.
If there's a chance that someone else ever wanted to do what you want to do, there's a chance that someone created a library for it. A few minutes Googling something like "python image library" will find you what you need, or let you know that someone hasn't created a library for your purposes.
I heard that Python is easy and powerful, but I don't know if I'm on the right track to learn it. I learn from online tutorials, I know basic maths calculation and printing strings, but how long will it take to develop something useful? I don't really know the exact uses of Python, though.
I'm not exactly sure what you're looking for, but I think one or more of the following may be the next step you're looking for.
Perhaps you would like to use a variety of different protocols for a networking program, you could check out Twisted.
Or perhaps if you would like to make a web application or blog you can check out Django.
Or perhaps you would like to make a GUI application, you could take a look at TkInter.
Or perhaps you would like to get into game programming, you could take a look at Pygame.
Or perhaps you would like to ... you can take a look at the Python Package Index.
How long will it take? This depends on your programming background in general. The best way is simply to jump into the topic you're interested in and start on a mini project.
Python is a general purpose language. You can use it to make a lot of different things, but it's best suited at stuff that doesn't require a lot of speed, since the high level features have a performance cost.
It's hard to tell how long it will take you to develop something useful. The other day I made a script to help on a small computer administration thing. You could do that with a week or two of experience (or maybe less), depending on your previous programming knowledge and the amount of time you put into studying. However, if you want to make something bigger (maybe an audio player, an IM client, mid-sized stuff like that), you probably need some weeks or months of practice. It depends a lot on the time and energy you invest in programming.
I'd suggest to follow either the official tutorial or Dive Into Python.
In general, it depends on you. Python can be used for simple or complex stuff, and for many different applications. It depends on what you want.
Have a look at Mark Pilgrim's freely available book called Dive Into Python. I think it's a better choice to start with than online tutorials. The best way to learn a language is to start to work on a project. As I read this book, I started to implement a simple image viewer. As I advanced with the book, I could refine the project progressively. Invent something that is interesting to you.
I also suggest you taking notes when you learn a programming language. When you learn something that can be useful later, make some notes with a simple example, e.g. how to read a text file line by line, convert int to str, convert str to int, basic list operations, etc. Later on you can use these building blocks in a larger project.
Like every other programming language In order to learn Python you need to write a program with it.
Find a pet project and use python to code it. I also recommend Dive into python" (like anyone else that answered your question).
A few months ago I've decided to learn IronPython (.NET implementation of python), I'vve started by reading "Dive into python" and a few tutorials and then I've started coding a simple board game using IronPython (you can read about it in my blog).
In order to learn a new programming language you need to use it and then you'll know how and where to use it.
The best way to learn how to do something useful is come up with something useful you want to do. Make sure it's not way out of your league, then do research to accomplish it. That's how a lot of programmers learn languages.
What other programming background do you have? What programming interests do you have -- web apps, numerical / scientific computations, games, ...? Python is good at many different things, for both beginners and experienced programmers, but the most fruitful approach(es) to it do depend on what you already know, and what really interests you!-)
Bram who invented bittorrent with python says python is good for writing protocols in addition to aforementioned webapps, games and general purpose. Compared to Java python solves same problem in less code and less ways in longer development and VM time where Java has more ways solve same problem in more code and faster VM and faster development time.
Making a comparison between Python, and other languages would not help, as there is always somebody who would find a reason to prefer one language instead of another.
If you want a scripting language that is powerful, but that it is easier to read than perl, that doesn't have a curly bracket syntax, and that allows you to learn something about object oriented programming, then Python is the language for you.
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I'm a newbie to programming. I had 1 semester of computer science (we used java). I got an A in the course and was able to do everything assigned, however I'm not sure I really understood it. I ignored the text and learned by looking at sample programs and then trial and error. I was ahead of the class except for two guys who came in knowing java or another OOP language.
I'd like to learn Python. I'm also going to build a second PC from extra parts I have and use linux. Basically, I want to enhance my knowledge of computers. Thats my motivation.
Now on learning python are there any good programming theory books that would be useful? Or should I read up on more on how computers operate on the lowest levels? I don't think I know enough to ask the question I want.
I guess to make it simple, I am asking what should I know to make the most of learning python. This is not for a career. This is from a desire to know. I am no longer a computer science major (it also would not have any direct applications to my anticipated career.)
I'm not looking to learn in "30 days" or "1 week" or whatever. So, starting from a very basic level is fine with me.
Thanks in advance. I did a search and didn't quite find what I was looking for.
UPDATE: Thanks for all the great advice. I found this site at work and couldn't find it on my home computer, so I am just getting to read now.
My recommendation is always to start at the high level of abstraction. You don't need to know how logic gates work and how you can use them to build a CPU -- it's cool stuff, but it's cool stuff that makes a lot more sense once you've messed around at the higher levels. Python is therefore an excellent choice as a learning aid.
How to Think Like A Computer Scientist: Learning With Python is available on the Internet and is an excellent introduction to the high-level concepts that make computers go. And it's even Python-specific.
If you're looking to have your brain turned inside-out, SICP will do a good job of it. I don't recommend it as a first text, though; it's heavy going.
Both of these books are high-level. They won't teach you anything about the low-level details like memory structures or what a CPU actually does, but that's something I would reserve for later anyway.
D'A
Specifically for the Python part of your question I can highly recommend http://www.diveintopython3.net/ by Mark Pilgrim. That's free and pretty well structured.
Python is a nice choice, you will have fun!
http://www.pythonchallenge.com/
I think this Challenge is perfect to get in touch with major python strengths and there is a nice forum with a lot of interessting Python Threads for each Level.
A lot of this depends on what your overall goal is for learning Python. Are you viewing it as learning a second language or getting a better understanding of computers and how to effectively use a programming language?
From what it sounds like you want to gain a better understanding about computers and be a better programmer. Learning a new languages such as Python will probably not help you in this respect. I still recommend learning Python if you're interested, but once you have learned one programming language, much of learning a new language is getting familiar with the syntax and data types (usually).
You had mentioned you were unsure about understanding the material in the class you took. If you feel you don't understand fundamental concepts (such as loops, classes, etc), then learning Python will help your understanding of programming as most books/guides revisit these concepts (Learning Python, 3rd Edition should help with this). If you understand these concepts, but you are unsure of how to apply these concepts, then my recommendation would be to learn about data structures and common algorithms (e.g. sorting, searching, etc).
Speaking from personal experience, I didn't know how to apply what I learned from the introductory programming class to personal programming projects. Learning about data structures from a class helped solidify those concepts I had previously learned by providing algorithms/data structures that build off of this previous knowledge. This class also allowed me to think differently about problems in terms of using these data structures.
To learn about the different types of data structures, see: http://en.wikipedia.org/wiki/List_of_data_structures. Usually, each data structure is useful for a specific purpose (e.g. binary search trees are good for searching sorted information). Unfortunately, I don't have any book recommendations (our class didn't use a book). Googling "Data Structures" should be a good starting point.
Data structures also got me to think about how efficient an implementation is. The "complexity" of an algorithm determines how long a given piece of code takes to run. This makes it easy to compare other implementations and determine which is better.
I would also like to comment that when it comes to learning computer concepts, the best way to learn is by doing. A book/class can only explain so much, and the rest you have to learn on your own. Each person learns differently, and programming is a way of taking the material you read about and think about it in a way that is best understood by you.
I hope I answered your question. At this point, you don't really need to worry about the underlying hardware. This is useful to know if you plan on doing this as a career (which you aren't), or want to make optimizations specific to the hardware you're running on (in which case, you wouldn't want to use Python). Python is a good choice to learn about data structures as it implements a lot of them for you, but it's important to know what they are used for.
If you are still in school, take a data structures class and see what you think of it. If you like it, I'd advise reconsidering the role of programming/CS in your career. You don't have to major in it, but consider a minor or at least a position that makes use of these skills you are learning. I say this because despite this not being your major, you are interested in understanding how a computer works and taking initiatives such as learning Python, building your own computer, and installing Linux.
If you have any further questions, feel free to ask. Good luck!
Python is a high-level language, so it wouldn't give you much direct benefit to learn how computers operate at the lowest levels.
Don't get me wrong - I do strongly believe that the low-level operation of a computer, e.g. assembly language and hardware, is something that every good programmer should be familiar with, because it does help you program more effectively in whatever language you are using, high-level or low-level. But it won't make much of a difference in your Python coding until you've gotten quite a bit of experience. If you're just starting out with Python, I would suggest staying away from the low-level operation of computers and concentrating on the basics of Python for now. Once you're comfortable with that, you can move on to something like C and then it might be appropriate to start looking at some lower-level stuff.
As for what you should know... not much, I guess. Python is a great language to start out programming in. It keeps simple things simple but it's rich enough to let you work your way up to a high level of complexity. I'd suggest probably looking at a tutorial; the one I happen to know is on the Python website, but I'm not claiming it's necessarily the best one for you. A Google search should give you plenty to get started with.
I started Python (as my first programming language) few months ago. I would recommend Learning Python, by Mark Lutz to begin with. But keep in mind that the key to learn well is to be open-minded, patient and willing to work and look up for things you don't understand.
Have fun!
I would suggest looking at the online book at http://www.diveintopython.org/ to learn python.
As for python projects, I would try learning the Django Framework. It is a framework for building web applications. They have a great tutorial for getting started with it. This would also give you experience building a webserver on a Linux box.
enhance my knowledge of computers
Well, what do you exactly mean by that? Python, or any other high level language, are designed to actually hide all the nasty details. That's one of the reasons, why it's apt for non-pros like (e.g. scientist).
If you want to know how stuff actually work, you should learn pure C. But then again, if you're not planning to have any career related to SC, there's not much point to it. Learn some more advanced algorithms and data structures instead. That'll result you more interesting, useful and is platform- and language-agnostic.
Short answer: all of them
Long answer:
Learning your first language is always a challenge, and after your Java experience, a lot of other languages will seem a lot simpler. That said, the real challenge in learning programming languages is learning when to use a particular language -- you can find decent docs for whatever you choose when the time comes.
As a concrete start, hop over to wikipedia and browse their categorical list of programming languages, click on all of the names you've ever heard (and anything else that catches your eye) and if the article has a code example, give it a minute or two to sink in (the rest of the article will help, of course). The point here is not to master every single language (which is (1) pointless and (2) impossible), but to get a handle on what is out there. For any language, there is a handful of other languages like it, and if you can at least read one language in most of those categories, you will have mastered a fairly large chunk of the programming universe. When a new project comes up, and something about it reminds you of some language you found, you can just learn that language as part of doing the project. It may sound like a lot of work, but after, say, your fifth big language, you completely lose count and just accidentally learn new ones all the time without noticing.
When you stop relating to one language as your home-language, you'll be able to learn from examples in other languages even if you've never programmed in them. Personally, I've only written a few Haskell programs, but being able to read Haskell has exposed me to a lot of ideas that I could recycle in more practical Scala and Python programs (oh yeah, after you learn Python, give Scala a browse and you'll probably never use Java again)
Even finding the best language for the job isn't the whole story. Having a lot of tools in your toolbox lets you throw together amazing stuff in short amounts of time by writing each piece of your project in the easiest language your could. This may not be appropriate for all projects, but, boy, can you make some impressive demos.
It takes many years to get to the point where no programming language is totally foreign (or at least foreign for more than a day of hacking), but I think it is a very healthy and realistic long-term plan to attempt to conquer a representative sample of each rough category. Good luck!
Since Python wasn't my first language, I found the Python Cookbook helpful for learning
What Python was capable of
The idiomatic, of "pythonic," way to do something.
Programming language teaching has always been associated with a cliche statement while learning. "Write programs to learn programming". I too would suggest the same.
If you are going to start from basics. This is of course, the most suggested starting point. It is lengthy, but it is worth all the time. http://www.diveintopython.org/
Because you are into some Java, this might be even better for you. http://www.swaroopch.com/notes/Python. Start either python 2.x or 3.0. Me personally am a fan of python 3. But for a starter it could be hard to get samples, and references to programs online. So for you 2.x might be better. But I leave it upto you.
Like I started "Write programs..". You can start here.
http://www.spoj.pl/ - a programming challenges site, where you can choose from a wide variety of topics, mostly algorithms and has huge question database. Of course the choice of programming languages is upto you.
http://projecteuler.net/ - a mathematical questions site, here you just have to submit an answer, cheating is allowed here, so be free to borrow logic from others, but try writing the program yourself.
After you think you have gained sufficient proficiency in python, you can try recipes in this book python cookbook http://www.amazon.com/Python-Cookbook-Alex-Martelli/dp/0596007973.
For application development, after you think you can handle it, start on wxPython or PyQt. I personally would suggest PyQt. It is responsive, fast, and has decent development cycle, I have not used WxPython for long, but few programs I wrote, long back, didn't feel so great. Yet again, its upto you.