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  • Python - Get Instance Variables

    - by Chris Bunch
    Is there a built-in method in Python to get an array of all a class' instance variables? For example, if I have this code: class hi: def __init__(self): self.ii = "foo" self.kk = "bar" Is there a way for me to do this: >>> mystery_method(hi) ["ii", "kk"] Thanks guys! Edit: I originally had asked for class variables erroneously. Thanks to all who brought this to my attention!

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  • How does MySQL's ORDER BY RAND() work?

    - by Eugene
    Hi, I've been doing some research and testing on how to do fast random selection in MySQL. In the process I've faced some unexpected results and now I am not fully sure I know how ORDER BY RAND() really works. I always thought that when you do ORDER BY RAND() on the table, MySQL adds a new column to the table which is filled with random values, then it sorts data by that column and then e.g. you take the above value which got there randomly. I've done lots of googling and testing and finally found that the query Jay offers in his blog is indeed the fastest solution: SELECT * FROM Table T JOIN (SELECT CEIL(MAX(ID)*RAND()) AS ID FROM Table) AS x ON T.ID >= x.ID LIMIT 1; While common ORDER BY RAND() takes 30-40 seconds on my test table, his query does the work in 0.1 seconds. He explains how this functions in the blog so I'll just skip this and finally move to the odd thing. My table is a common table with a PRIMARY KEY id and other non-indexed stuff like username, age, etc. Here's the thing I am struggling to explain SELECT * FROM table ORDER BY RAND() LIMIT 1; /*30-40 seconds*/ SELECT id FROM table ORDER BY RAND() LIMIT 1; /*0.25 seconds*/ SELECT id, username FROM table ORDER BY RAND() LIMIT 1; /*90 seconds*/ I was sort of expecting to see approximately the same time for all three queries since I am always sorting on a single column. But for some reason this didn't happen. Please let me know if you any ideas about this. I have a project where I need to do fast ORDER BY RAND() and personally I would prefer to use SELECT id FROM table ORDER BY RAND() LIMIT 1; SELECT * FROM table WHERE id=ID_FROM_PREVIOUS_QUERY LIMIT 1; which, yes, is slower than Jay's method, however it is smaller and easier to understand. My queries are rather big ones with several JOINs and with WHERE clause and while Jay's method still works, the query grows really big and complex because I need to use all the JOINs and WHERE in the JOINed (called x in his query) sub request. Thanks for your time!

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  • MYSQL in PHPMYADMIN - create table relationship from one table

    - by Stanley DecoWood
    I want to create a table relationship with MYSQL PHPMYADMIN. I have this Create table: CREATE TABLE students(code_students int(8)not null AUTO_INCREMENT, name_students varchar(25), age_students int(3), degree_program varchar(25), code_advisor int(8)not null, primary key(code_students, code_advisor) ); and i want to make a create table named advise relationship between code_students, code_advisor.

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  • PHP and MySql trouble

    - by Espen Arnoy
    I am having trouble making this seemingly simple MySql query work. Can anyone spot the problem? <?php include "config.php"; $offerid = $_POST["offerid"]; $ip = $_SERVER["REMOTE_ADDR"]; mysql_query("INSERT INTO voted (offerid,ip) VALUES (".$offerid.",".$ip.")"); ?>

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  • Type derivation in python?

    - by aXqd
    In Perl, I can do this: push(@{$h->[x]}, y); Can I simplify the following python codes according to above Perl example? if x not in h: h[x] = [] h[x].append(y) I want to simplify this, because it goes many places in my code, (and I cannot initialize all possible x with []). I do not want to make it a function, because there is no 'inline' keyword. Any ideas?

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  • Launch a webpage on a Firefox (win) tab using Python

    - by Leandro Ardissone
    Hi, I'm trying to launch a website url in a new tab using python in that way, but it didn't worked in these both ways: Method 1: os.system('C:\Program Files\Mozilla Firefox\Firefox.exe -new-tab http://www.google.com/'); and Method 2: os.startfile('C:\Program Files\Mozilla Firefox\Firefox.exe -new-tab http://www.google.com/'); If I don't add the parameters (-new-tab http://www.google.com/) it works, opening the default page.

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  • Python: using doctests for classes

    - by Adam Matan
    Hi, Is it possible to use Python's doctest concept for classes, not just functions? If so, where shall I put the doctests - at the class' docstring, or at the constructor's docstring? To clarify, I'm looking for something like: class Test: """ >>> a=Test(5) >>> a.multiply_by_2() 10 """ def __init__(self, number): self._number=number def multiply_by_2(self): return self._number*2 Thanks in advance, Adam

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  • Writing csv files with python with exact formatting parameters

    - by Ben Harrison
    I'm having trouble with processing some csv data files for a project. The project's programmer has moved onto greener pastures, and now I'm trying to finish the data analysis up (I did/do the statistical analysis.) The programmer suggested using python/csv reader to help break down the files, which I've had some success with, but not in a way I can use. This code is a little different from what I was trying before. I am essentially attempting to create an array. In the raw data format, the first 7 rows contain no data, and then each column contains 50 experiments, each with 4000 rows, for 200000 some rows total. What I want to do is take each column, and make it an individual csv file, with each experiment in its own column. So it would be an array of 50 columns and 4000 rows for each data type. The code here does break down the correct values, I think the logic is okay, but it is breaking down the opposite of how I want it. I want the separators without quotes (the commas and spaces) and I want the element values in quotes. Right now it is doing just the opposite for both, element values with no quotes, and the separators in quotes. I've spent several hours trying to figure out how to do this to no avail, import csv ifile = open('00_follow_maverick.csv') epistemicfile = open('00_follower_maverick_EP.csv', 'w') reader = csv.reader(ifile) colnum = 0 rownum = 0 y = 0 z = 8 for column in reader: rownum = 4000 * y + z for element in column: writer = csv.writer(epistemicfile) if y <= 50: y = y + 1 writer.writerow([element]) writer.writerow(',') rownum = x * y + z if y > 50: y = 0 z = z + 1 writer.writerow(' ') rownum = x * y + z if z >= 4008: break What is going on: I am taking each row in the raw data file in iterations of 4000, so that I can separate them with commas for the 50 experiments. When y, the experiment indicator here, reaches 50, it resets back to experiment 0, and adds 1 to z, which tells it which row to look at, by the formula of 4000 * y + z. When it completes the rows for all 50 experiments, it is finished. The problem here is that I don't know how to get python to write the actual values in quotes, and my separators outside of quotes. Any help will be most appreciated. Apologies if this seems a stupid question, I have no programming experience, this is my first attempt ever. Thank you.

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  • Problem reading from 3 tables in mysql

    - by user225269
    What do I do, I need to fetch data from 3 tables in mysql, here is my current query. All of the tables contain the IDNO which has 03A45 number. But this query isnt returning any results: SELECT * FROM father, mother, parents WHERE father.IDNO=mother.IDNO=parents.IDNO AND mother.IDNO='03A45' AND father.IDNO='03A45' AND parents.IDNO='03A45' What would be the correct query for this? All of the tables have the IDNO as primary key.

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  • Reading a MIDI file in Python

    - by Logan
    I want to be able to read events from a MIDI file in Python. I have looked for libraries, but can't find one that works with my MIDI file in windows. I do not need to do anything real time, and just want a simple library that gives me events and times. Would it be easier to write one for myself? Any help would be appreciated.

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  • Using MySQL on Visual Studio 2008

    - by Diego
    I am using the ODBC connector to access a MySQL db from visual studio 2008 and i am facing performance problems when dealing with crystal reports and to solve this i need a native connector to visual studio. if someone has had a similar problem and knows a solution or tools ( freeware preferable ) , i would be really grateful.

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  • For-loops in python

    - by Znarkus
    What is the best way of doing this in Python? for (v = n / 2 - 1; v >= 0; v--) I actually tried Google first, but as far as I can see the only solution would be to use while.

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  • How to determine which my.cnf mysql is using

    - by japancheese
    Hello, Is there a way I can figure out which my.cnf mysql is currently using? The reason is because it's using the correct socket file to connect, but I can't figure out exactly which (if any) my.cnf it's using or trying to use so I can manually set the correct path on my local machine.

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  • Get CGI Fields from URL Python

    - by user299196
    When using the cgi module in Python, I can't seem to figure out how to extract CGI variables in the URL. For example if the url servercgi.py?name=user , how do I get 'name' after import cgi? For some reason, form.getvalue and form['user'] do not work but if I print the object, I see something like FieldStorage(None, None, [MiniFieldStoreage('name', 'user')]).

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