Pollyanna posted:

Is there, uh...an explanation on how to use Requests? Say I want to get the text on http://www.alcyone.com/oo/ , like the title and then a list of all the links there. The Requests quickstart guide talks about getting post data and keys and values and such...but no real explanation on "hey get this text". I am not good at HTTP, is this what Requests is good for? Or is it more complicated than that?

the posted:

Trying to figure out how to make an n * n matrix in Python and then populate it with random numbers. The user specifies a size (example, 5 makes a 5x5 matrix). I know how to make any matrix, as in:

Python code:

numpy.matrix([[2,3],[5,6]])

Would make

code:

[2 3]
[5 6]

But how do I create one without knowing the size?

Pollyanna posted:

Is there, uh...an explanation on how to use Requests? Say I want to get the text on http://www.alcyone.com/oo/ , like the title and then a list of all the links there. The Requests quickstart guide talks about getting post data and keys and values and such...but no real explanation on "hey get this text". I am not good at HTTP, is this what Requests is good for? Or is it more complicated than that?

Dren posted:

QTimer should be protecting you from a lot of the mess that this code would cause if it were executed in a separate thread because it executes its callback in the event thread. If it didn't and the callback was executing from a different thread, you'd have bad problems if you happened to change parameters while the callback was executing.

Here's an effort to decouple metronome behavior and instrument playing behavior. The metronome is in charge of bpm, meter, and current_beat. The instrument is in charge of the other stuff. The way it's set up the metronome's start method accepts the play_beat callback function, which has been modified to accept downbeat as an argument. If you wanted you could add a method to it to allow other instruments to be added to the timer's callback. Might be interesting.


Decoupling the functionality into Instrument and Metronome like this also gives another possible extension if you allow multiple instruments, global volume and per-instrument volume. You could add a volume property to the metronome, which would be the global volume, and let the volume setting on the instrument be a percentage of the global volume.

Hammerite posted:

I assume

Python code:

numpy.matrix([[0] * 5] * 5)

Dominoes posted:

You could use regular expressions to extract the links from the HTML.

quote:

You can't parse [X]HTML with regex. Because HTML can't be parsed by regex. Regex is not a tool that can be used to correctly parse HTML. As I have answered in HTML-and-regex questions here so many times before, the use of regex will not allow you to consume HTML. Regular expressions are a tool that is insufficiently sophisticated to understand the constructs employed by HTML. HTML is not a regular language and hence cannot be parsed by regular expressions. Regex queries are not equipped to break down HTML into its meaningful parts. so many times but it is not getting to me. Even enhanced irregular regular expressions as used by Perl are not up to the task of parsing HTML. You will never make me crack. HTML is a language of sufficient complexity that it cannot be parsed by regular expressions. Even Jon Skeet cannot parse HTML using regular expressions. Every time you attempt to parse HTML with regular expressions, the unholy child weeps the blood of virgins, and Russian hackers pwn your webapp. Parsing HTML with regex summons tainted souls into the realm of the living. HTML and regex go together like love, marriage, and ritual infanticide. The <center> cannot hold it is too late. The force of regex and HTML together in the same conceptual space will destroy your mind like so much watery putty. If you parse HTML with regex you are giving in to Them and their blasphemous ways which doom us all to inhuman toil for the One whose Name cannot be expressed in the Basic Multilingual Plane, he comes. HTML-plus-regexp will liquify the n​erves of the sentient whilst you observe, your psyche withering in the onslaught of horror. Rege̿̔̉x-based HTML parsers are the cancer that is killing StackOverflow it is too late it is too late we cannot be saved the trangession of a chi͡ld ensures regex will consume all living tissue (except for HTML which it cannot, as previously prophesied) dear lord help us how can anyone survive this scourge using regex to parse HTML has doomed humanity to an eternity of dread torture and security holes using regex as a tool to process HTML establishes a breach between this world and the dread realm of c͒ͪo͛ͫrrupt entities (like SGML entities, but more corrupt) a mere glimpse of the world of reg​ex parsers for HTML will ins​tantly transport a programmer's consciousness into a world of ceaseless screaming, he comes, the pestilent slithy regex-infection wil​l devour your HT​ML parser, application and existence for all time like Visual Basic only worse he comes he comes do not fi​ght he com̡e̶s, ̕h̵i​s un̨ho͞ly radiańcé destro҉ying all enli̍̈́̂̈́ghtenment, HTML tags lea͠ki̧n͘g fr̶ǫm ̡yo​͟ur eye͢s̸ ̛l̕ik͏e liq​uid pain, the song of re̸gular exp​ression parsing will exti​nguish the voices of mor​tal man from the sp​here I can see it can you see ̲͚̖͔̙î̩́t̲͎̩̱͔́̋̀ it is beautiful t​he final snuffing of the lie​s of Man ALL IS LOŚ͖̩͇̗̪̏̈́T ALL I​S LOST the pon̷y he comes he c̶̮omes he comes the ich​or permeates all MY FACE MY FACE ᵒh god no NO NOO̼O​O NΘ stop the an​*̶͑̾̾​̅ͫ͏̙̤g͇̫͛͆̾ͫ̑͆l͖͉̗̩̳̟̍ͫͥͨe̠̅s ͎a̧͈͖r̽̾̈́͒͑e n​ot rè̑ͧ̌aͨl̘̝̙̃ͤ͂̾̆ ZA̡͊͠͝LGΌ ISͮ̂҉̯͈͕̹̘̱ TO͇̹̺ͅƝ̴ȳ̳ TH̘Ë͖́̉ ͠P̯͍̭O̚​N̐Y̡ H̸̡̪̯ͨ͊̽̅̾̎Ȩ̬̩̾͛ͪ̈́̀́͘ ̶̧̨̱̹̭̯ͧ̾ͬC̷̙̲̝͖ͭ̏ͥͮ͟Oͮ͏̮̪̝͍M̲̖͊̒ͪͩͬ̚̚͜Ȇ̴̟̟͙̞ͩ͌͝S̨̥̫͎̭ͯ̿̔̀ͅ

Dominoes posted:

You could use regular expressions to extract the links from the HTML.

the posted:

Trying to figure out how to make an n * n matrix in Python and then populate it with random numbers. The user specifies a size (example, 5 makes a 5x5 matrix).

the posted:

But how do I create one without knowing the size?

Dren posted:

The biggest changes you will notice are that print is a function and that division between two integers will give you a float result (if the result has a fractional part) instead of a truncated int.

Nippashish posted:

More generally, you can allocate blocks using ones/zeros/np.random.whatever and fill them in element by element or stitch them together using hstack/vstack/dstack/concatenate/kron/etc to build up structured arrays.

Hammerite posted:

I assume

Python code:

numpy.matrix([[0] * 5] * 5)

yaoi prophet posted:

I totally write classes that I'll only ever have one instance of at a time, it helps group functionality together. Same with functions that I'll only call once.

Hot Dog Day #42 posted:

This might work for numpy, but it's a really bad habit to get into for making matrix-type nested lists, for the following reason:

Python code:

>>> L = [[0]*5]*5
>>> L
[[0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]
>>> L[0][0] = 1
>>> L
[[1, 0, 0, 0, 0], [1, 0, 0, 0, 0], [1, 0, 0, 0, 0], [1, 0, 0, 0, 0], [1, 0, 0, 0, 0]]

The problem is the last *5, which makes a list containing 5 references to the same list [0,0,0,0,0], so that any change to one of those lists changes all the lists.

Better would be

Python code:

L = [[0 for x in range(5)] for y in range(5)]

which gives the expected behavior after L[0][0] = 1.

SirPablo posted:

This might be in left-field/hail mary territory because it is such a niche use, but any suggestion how to open grib2 files using the PythonX,Y framework? I was using python 2.5 before and had a mix of library that worked for what I do (working with a lot of weather model data that is stored in the grib/grib2 format) but decided to try x,y to just have as many tools available as I could. Well, now I'm missing this one small but important piece. I found this but I got the same error indicated in the later comments. Any suggestions (besides reverting back to my 2.5 stuff)?

Dominoes posted:

regular expressions

Hot Dog Day #42 posted:

Requests will get you the file, but you'll need some kind of parser like Beautiful Soup to actually do anything with the file (like grabbing all the links, as in your example).

Thermopyle posted:

Pollyanna posted:

nnnnnnnnoooooooooooooooooooooooooooo

I hate those. They're such a pain in the rear end to figure out and type. It's one of those things that you're likely to never be able to write on-the-fly. I'm gonna have to use them eventually though, and I dread that day.


This on the other hand makes it all better. Thanks for the link!

Thermopyle posted:

Try reading the rest of the posts after those two.

the posted:

Why is this second line returning an invalid syntax?

Python code:

def f(r):
    return numpy.sin(r)/((r)^^0.5)

keyframe posted:

EDIT: Found it after googling a bit! I needed to use "\" at the end of the line to continue the line.

BeefofAges posted:

For most cases when you actually need a regex (not for parsing HTML) it's way easier to use http://txt2re.com/ than to try to develop a regex by hand.

SirPablo posted:

This might be in left-field/hail mary territory because it is such a niche use, but any suggestion how to open grib2 files using the PythonX,Y framework? I was using python 2.5 before and had a mix of library that worked for what I do (working with a lot of weather model data that is stored in the grib/grib2 format) but decided to try x,y to just have as many tools available as I could. Well, now I'm missing this one small but important piece. I found this but I got the same error indicated in the later comments. Any suggestions (besides reverting back to my 2.5 stuff)?

Gangsta Lean posted:

I don't know anything about pythonxy, never heard of it until now, but have you looked into using GDAL? I also use lots of weather model data and GDAL is my goto library for reading grib2. It's a C++ library, but it has bindings to many languages including python by using SWIG. With python, you can read each timestep's data as a numpy array.

GDAL is very powerful and can reproject data, load and save many file formats through a common API, and is used by many mapping tools under the hood since it has such a large number of standard capabilities.

I don't know about its python 2.5 support, I use it with 2.7.

code:

import osgeo.gdal
osgeo.gdal.UseExceptions()
osgeo.gdal.SetConfigOption('GRIB_NORMALIZE_UNITS', 'NO')

dataset = osgeo.gdal.Open('my filename')
for band_index in xrange(dataset.RasterCount):
    band = dataset.GetRasterBand(band_index + 1)
    md = band.GetMetadata()
    geotransform = dataset.GetGeoTransform()
    wkt = dataset.GetProjection()
    data = band.ReadAsArray()

Gangsta Lean posted:

I don't know anything about pythonxy, never heard of it until now, but have you looked into using GDAL? I also use lots of weather model data and GDAL is my goto library for reading grib2. It's a C++ library, but it has bindings to many languages including python by using SWIG. With python, you can read each timestep's data as a numpy array.

GDAL is very powerful and can reproject data, load and save many file formats through a common API, and is used by many mapping tools under the hood since it has such a large number of standard capabilities.

I don't know about its python 2.5 support, I use it with 2.7.

code:

import osgeo.gdal
osgeo.gdal.UseExceptions()
osgeo.gdal.SetConfigOption('GRIB_NORMALIZE_UNITS', 'NO')

dataset = osgeo.gdal.Open('my filename')
for band_index in xrange(dataset.RasterCount):
    band = dataset.GetRasterBand(band_index + 1)
    md = band.GetMetadata()
    geotransform = dataset.GetGeoTransform()
    wkt = dataset.GetProjection()
    data = band.ReadAsArray()

keyframe posted:

Another day another question

I am trying to write a function that appends a user input number to the end of the list, this is what I have so far:

code:

numbers = [1,4,5]


def list_adder(n):
    n.append(int(input("enter number")))
    return n
  
    
    
print list_adder(numbers)

It works when you enter a number. I have been trying to write a if statement inside the function that checks if the input is numbers and give a "not a number" message if it is string. Did some search online and it seems the way to do a check for that is .isdigit() but it seems isdigit does not work with lists. What can I do here to accomplish this? Using python 2.7.5 by the way.