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• Does writing program using global variables is safer?

  - by ZoZo123

  I was reading about buffer, stack and heap overflows. I read this post as well. my question is like that: if I use only global variables in my code, can I say it prevents all the exploits of overflow? let's say I have this buffers in code declared in the global scope: char buf1[10]; char buf2[100]; If I send buf1 as the buffer to recv(int s, char *buf, int len,int flags); I will overwrite the data segment and may ruin the buf2 content, right? Would I be able to run a code from it because as I know it is not a code segment and data segment is not executable. Can we conclude that using Globals is the safest way?

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• just-in-time list

  - by intuited

  I'd like to know if there is a class available, either in the standard library or in pypi, that fits this description. The constructor would take an iterator. It would implement the container protocol (ie _getitem_, _len_, etc), so that slices, length, etc., would work. In doing so, it would iterate and retain just enough values from its constructor argument to provide whatever information was requested. So if jitlist[6] was requested, it would call self.source.next() 7 times, save those elements in its list, and return the last one. This would allow downstream code to use it as a list, but avoid unnecessarily instantiating a list for cases where list functionality was not needed, and avoid allocating memory for the entire list if only a few members ended up being requested. It seems like a pretty easy one to write, but it also seems useful enough that it's likely that someone would have already made it available in a module.

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• python multiprocessing.Process.Manager not producing consistent results?

  - by COpython

  I've written the following code to illustrate the problem I'm seeing. I'm trying to use a Process.Manager.list() to keep track of a list and increment random indices of that list. Each time there are 100 processes spawned, and each process increments a random index of the list by 1. Therefore, one would expect the SUM of the resulting list to be the same each time, correct? I get something between 203 and 205. from multiprocessing import Process, Manager import random class MyProc(Process): def __init__(self, A): Process.__init__(self) self.A = A def run(self): i = random.randint(0, len(self.A)-1) self.A[i] = self.A[i] + 1 if __name__ == '__main__': procs = [] M = Manager() a = M.list(range(15)) print('A: {0}'.format(a)) print('sum(A) = {0}'.format(sum(a))) for i in range(100): procs.append(MyProc(a)) map(lambda x: x.start(), procs) map(lambda x: x.join(), procs) print('A: {0}'.format(a)) print('sum(A) = {0}'.format(sum(a)))

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• Python, Matplotlib, subplot: How to set the axis range?

  - by someone

  How can I set the y axis range of the second subplot to e.g. [0,1000] ? The FFT plot of my data (a column in a text file) results in a (inf.?) spike so that the actual data is not visible. pylab.ylim([0,1000]) has no effect, unfortunately. This is the whole script: # based on http://www.swharden.com/blog/2009-01-21-signal-filtering-with-python/ import numpy, scipy, pylab, random xs = [] rawsignal = [] with open("test.dat", 'r') as f: for line in f: if line[0] != '#' and len(line) > 0: xs.append( int( line.split()[0] ) ) rawsignal.append( int( line.split()[1] ) ) h, w = 3, 1 pylab.figure(figsize=(12,9)) pylab.subplots_adjust(hspace=.7) pylab.subplot(h,w,1) pylab.title("Signal") pylab.plot(xs,rawsignal) pylab.subplot(h,w,2) pylab.title("FFT") fft = scipy.fft(rawsignal) #~ pylab.axis([None,None,0,1000]) pylab.ylim([0,1000]) pylab.plot(abs(fft)) pylab.savefig("SIG.png",dpi=200) pylab.show() Other improvements are also appreciated!

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• how to test if a string is a valid UTF16 string?

  - by superb

  I am using mongodb and javascript to do some string processing. Now I got some error like: Sun May 23 07:42:20 Assertion failure JS_EncodeCharacters( _context , s , srclen , dst , &len) scripting/engine_spidermonkey.cpp 152 0x80f4f7e 0x80f8794 0x811525b 0x811a953 0x8119fc4 0x8111bc5 0x81b408e 0x81c4ee7 0x81b4a10 0x817a881 0x817a7d8 0x817a6e2 0x811e1bb 0x80a777b 0x80a8f8a 0xb7cb2455 0x80a37a1 mongodb-linux-i686-1.4.2/bin/mongo(_ZN5mongo12sayDbContextEPKc+0xfe) [0x80f4f7e] After doing some google, I find that JS_EncodeCharacters return false if the input is not a valid UTF16 string. (if spidermonkey is build with UTF-8 enabled) So I was wondering how to test if the input string if a proper UTF16 string? so I can skip such kind of string to avoid problem ... Thanks

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• MS Access: Order of Events in event ApplyFilter (ADP Project)

  - by Jose Valdes

  I'm having problems with the execution of ServerFilterByForm in Access 2003 When I apply the entered filter it returns the requested data but after it appear on screen (Form) it disappears. Don't know why this is happening Does anyone had the same problem? How can it be solved? Heris is part of the code Private Sub Form_ApplyFilter(Cancel As Integer, ApplyType As Integer) Dim stSql As String If Len(ServerFilter) > 0 Then stSql = "SELECT * FROM v_InitialReviewQuery " & _ " WHERE " + ServerFilter & _ " ORDER BY acctnumber" Else stSql = "SELECT top 1 * FROM v_InitialReviewQuery ORDER BY acctnumber" End If Me.RecordSource = stSql End Sub

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• Need help understanding some Python code

  - by Yarin

  I'm new to Python, and stumped by this piece of code from the Boto project: class SubdomainCallingFormat(_CallingFormat): @assert_case_insensitive def get_bucket_server(self, server, bucket): return '%s.%s' % (bucket, server) def assert_case_insensitive(f): def wrapper(*args, **kwargs): if len(args) == 3 and not (args[2].islower() or args[2].isalnum()): raise BotoClientError("Bucket names cannot contain upper-case " \ "characters when using either the sub-domain or virtual " \ "hosting calling format.") return f(*args, **kwargs) return wrapper Trying to understand what's going on here. What is the '@' symbol in @assert_case_sensitive ? What do the args *args, **kwargs mean? What does 'f' represent? Thanks!

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• Better ways to print out column names when using cx_Oracle

  - by philipjkim

  Found an example using cx_Oracle, this example shows all the information of Cursor.description. import cx_Oracle from pprint import pprint connection = cx_Oracle.Connection("%s/%s@%s" % (dbuser, dbpasswd, oracle_sid)) cursor = cx_Oracle.Cursor(connection) sql = "SELECT * FROM your_table" cursor.execute(sql) data = cursor.fetchall() print "(name, type_code, display_size, internal_size, precision, scale, null_ok)" pprint(cursor.description) pprint(data) cursor.close() connection.close() What I wanted to see was the list of Cursor.description[0](name), so I changed the code: import cx_Oracle import pprint connection = cx_Oracle.Connection("%s/%s@%s" % (dbuser, dbpasswd, oracle_sid)) cursor = cx_Oracle.Cursor(connection) sql = "SELECT * FROM your_table" cursor.execute(sql) data = cursor.fetchall() col_names = [] for i in range(0, len(cursor.description)): col_names.append(cursor.description[i][0]) pp = pprint.PrettyPrinter(width=1024) pp.pprint(col_names) pp.pprint(data) cursor.close() connection.close() I think there will be better ways to print out the names of columns. Please get me alternatives to the Python beginner. :-)

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• Have I checked every consecutive subset of this list?

  - by Nathan

  I'm trying to solve problem 50 on Project Euler. Don't give me the answer or solve it for me, just try to answer this specific question. The goal is to find the longest sum of consecutive primes that adds to a prime below one million. I use wrote a sieve to find all the primes below n, and I have confirmed that it is correct. Next, I am going to check the sum of each subset of consecutive primes using the following method: I have a empty list sums. For each prime number, I add it to each element in sums and check the new sum, then I append the prime to sums. Here it is in python primes = allPrimesBelow(1000000) sums = [] for p in primes: for i in range(len(sums)): sums[i] += p check(sums[i]) sums.append(p) I want to know if I have called check() for every sum of two or more consecutive primes below one million The problem says that there is a prime, 953, that can be written as the sum of 21 consecutive primes, but I am not finding it.

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• poplib and email module will not reloop through a message if it has alread read it

  - by user1440925

  I'm currently trying to write a script that gets messages from my gmail account but I'm noticing a problem. If poplib loops through a message in my inbox it will never loop through it again. Here is my code import poplib, string, email user = "[email protected]" password = "p0ckystyx" message = "" mail = poplib.POP3_SSL('pop.gmail.com') mail.user(user) mail.pass_(password) iMessageCount = len(mail.list()[1]) message = "" msg = mail.retr(iMessageCount) str = string.join(msg[1], "\n") frmMail = email.message_from_string(str) for part in frmMail.walk(): if part.get_content_type() == "text/plain": print part.get_payload() mail.quit() Every time I run this script it goes to the next newest email and just skips over the email that was shown last time it was run.

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• why am i getting an error SyntaxError : invalid syntax for this code

  - by eragon1189

  This is a code in python which calculates f (x) =? ((-1)*x)/(x*x+n*n) n from 1 to infinite.... correct to 0.0001, for the range 1 < x < 100 in steps of 0.1.But i am getting an syntax error,as i am new to programming in python... from scipy import * from matplotlib.pyplot import * x=arange(0.1,100,0.1) f=zeros(len(x)) s=-1 for n in range (1,10000): t=s*x/(x*x+n*n) f +=t s =-s if max(abs(t))< 1e-4 break for xx in c_[x,f]: print "%f %f" % (xx[0],xx[1])

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• Python OpenGL Can't Redraw Scene

  - by RobbR

  I'm getting started with OpenGL and shaders using GLUT and PyOpenGL. I can draw a basic scene but for some reason I can't get it to update. E.g. any changes I make during idle(), display(), or reshape() are not reflected. Here are the methods: def display(self): glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ) glMatrixMode(GL_MODELVIEW) glLoadIdentity() glUseProgram(self.shader_program) self.m_vbo.bind() glEnableClientState( GL_VERTEX_ARRAY ) glVertexPointerf(self.m_vbo) glDrawArrays(GL_TRIANGLES, 0, len(self.m_vbo)) glutSwapBuffers() glutReportErrors() def idle(self): test_change += .1 self.m_vbo = vbo.VBO( array([ [ test_change, 1, 0 ], # triangle [ -1,-1, 0 ], [ 1,-1, 0 ], [ 2,-1, 0 ], # square [ 4,-1, 0 ], [ 4, 1, 0 ], [ 2,-1, 0 ], [ 4, 1, 0 ], [ 2, 1, 0 ], ],'f') ) glutPostRedisplay() def begin(self): glutInit() glutInitWindowSize(400, 400) glutCreateWindow("Simple OpenGL") glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB) glutDisplayFunc(self.display) glutReshapeFunc(self.reshape) glutMouseFunc(self.mouse) glutMotionFunc(self.motion) glutIdleFunc(self.idle) self.define_shaders() glutMainLoop() I'd like to implement a time step in idle() but even basic changes to the vertices or tranlastions and rotations on the MODELVIEW matrix don't display. It just puts up the initial state and does not update. Am I missing something?

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• Downsampling the number of entries in a list (without interpolation)

  - by Dave

  I have a Python list with a number of entries, which I need to downsample using either: A maximum number of rows. For example, limiting a list of 1234 entries to 1000. A proportion of the original rows. For example, making the list 1/3 its original length. (I need to be able to do both ways, but only one is used at a time). I believe that for the maximum number of rows I can just calculate the proportion needed and pass that to the proportional downsizer: def downsample_to_max(self, rows, max_rows): return downsample_to_proportion(rows, max_rows / float(len(rows))) ...so I really only need one downsampling function. Any hints, please? EDIT The list contains objects, not numeric values so I do not need to interpolate. Dropping objects is fine.

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• optimize python code

  - by user283405

  i have code that uses BeautifulSoup library for parsing. But it is very slow. The code is written in such a way that threads cannot be used. Can anyone help me about this? I am using beautifulsoup library for parsing and than save in DB. if i comment the save statement, than still it takes time so there is no problem with database. def parse(self,text): soup = BeautifulSoup(text) arr = soup.findAll('tbody') for i in range(0,len(arr)-1): data=Data() soup2 = BeautifulSoup(str(arr[i])) arr2 = soup2.findAll('td') c=0 for j in arr2: if str(j).find("<a href=") > 0: data.sourceURL = self.getAttributeValue(str(j),'<a href="') else: if c == 2: data.Hits=j.renderContents() #and few others... #... c = c+1 data.save() Any suggestions? Note: I already ask this question here but that was closed due to incomplete information.

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• Alternative to "assign to a function call" in a python

  - by Pythonista's Apprentice

  I'm trying to solve this newbie puzzle: I've created this function: def bucket_loop(htable, key): bucket = hashtable_get_bucket(htable, key) for entry in bucket: if entry[0] == key: return entry[1] else: return None And I have to call it in two other functions (bellow) in the following way: to change the value of the element entry[1] or to append to this list (entry) a new element. But I can't do that calling the function bucket_loop the way I did because "you can't assign to function call" (assigning to a function call is illegal in Python). What is the alternative (most similar to the code I wrote) to do this (bucket_loop(htable, key) = value and hashtable_get_bucket(htable, key).append([key, value]))? def hashtable_update(htable, key, value): if bucket_loop(htable, key) != None: bucket_loop(htable, key) = value else: hashtable_get_bucket(htable, key).append([key, value]) def hashtable_lookup(htable, key): return bucket_loop(htable, key) Thanks, in advance, for any help! This is the rest of the code to make this script works: def make_hashtable(size): table = [] for unused in range(0, size): table.append([]) return table def hash_string(s, size): h = 0 for c in s: h = h + ord(c) return h % size def hashtable_get_bucket(htable, key): return htable[hash_string(key, len(htable))] Similar question (but didn't help me): Python: Cannot Assign Function Call

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• Using a Loop to add objects to a list(python)

  - by Will

  Hey guys so im trying to use a while loop to add objects to a list. Heres bascially what i want to do: (ill paste actually go after) class x: blah blah choice = raw_input(pick what you want to do) while(choice!=0): if(choice==1): Enter in info for the class: append object to list (A) if(choice==2): print out length of list(A) if(choice==0): break ((((other options)))) as im doing this i can get the object to get added to the list, but i am stuck as to how to add multiple objects to the list in the loop. Here is my actual code i have so far... print "Welcome to the Student Management Program" class Student: def init (self, name, age, gender, favclass): self.name = name self.age = age self.gender = gender self.fac = favclass choice = int(raw_input("Make a Choice: " )) while (choice !=0): if (guess==1): print("STUDENT") namer = raw_input("Enter Name: ") ager = raw_input("Enter Age: ") sexer = raw_input("Enter Sex: ") faver = raw_input("Enter Fav: ") elif(guess==2): print "TESTING LINE" elif(guess==3): print(len(a)) guess=int(raw_input("Make a Choice: ")) s = Student(namer, ager, sexer, faver) a =[]; a.append(s) raw_input("Press enter to exit") any help would be greatly appreciated!

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• idiomatic way to take groups of n items from a list in Python?

  - by Wang

  Given a list A = [1 2 3 4 5 6] Is there any idiomatic (Pythonic) way to iterate over it as though it were B = [(1, 2) (3, 4) (5, 6)] other than indexing? That feels like a holdover from C: for a1,a2 in [ (A[i], A[i+1]) for i in range(0, len(A), 2) ]: I can't help but feel there should be some clever hack using itertools or slicing or something. (Of course, two at a time is just an example; I'd like a solution that works for any n.) Edit: related http://stackoverflow.com/questions/1162592/iterate-over-a-string-2-or-n-characters-at-a-time-in-python but even the cleanest solution (accepted, using zip) doesn't generalize well to higher n without a list comprehension and *-notation.

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• Python: find <title>

  - by Peter

  I have this: response = urllib2.urlopen(url) html = response.read() begin = html.find('<title>') end = html.find('</title>',begin) title = html[begin+len('<title>'):end].strip() if the url = http://www.google.com then the title have no problem as "Google", but if the url = "http://www.britishcouncil.org/learning-english-gateway" then the title become "<!doctype html public "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML> <HEAD> <base href="http://www.britishcouncil.org/" /> <META http-equiv="Content-Type" Content="text/html;charset=utf-8"> <meta name="WT.sp" content="Learning;Home Page Smart View" /> <meta name="WT.cg_n" content="Learn English Gateway" /> <META NAME="DCS.dcsuri" CONTENT="/learning-english-gateway.htm">..." What is actually happening, why I couldn't return the "title"?

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• Efficient way to combine results of two database queries.

  - by ensnare

  I have two tables on different servers, and I'd like some help finding an efficient way to combine and match the datasets. Here's an example: From server 1, which holds our stories, I perform a query like: query = """SELECT author_id, title, text FROM stories ORDER BY timestamp_created DESC LIMIT 10 """ results = DB.getAll(query) for i in range(len(results)): #Build a string of author_ids, e.g. '1314,4134,2624,2342' But, I'd like to fetch some info about each author_id from server 2: query = """SELECT id, avatar_url FROM members WHERE id IN (%s) """ values = (uid_list) results = DB.getAll(query, values) Now I need some way to combine these two queries so I have a dict that has the story as well as avatar_url and member_id. If this data were on one server, it would be a simple join that would look like: SELECT * FROM members, stories WHERE members.id = stories.author_id But since we store the data on multiple servers, this is not possible. What is the most efficient way to do this? Thanks.

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• I'm an idiot/blind and I can't find why I'm getting a list index error. Care to take a look at these 20 or so lines?

  - by Meff

  Basically it's supposed to take a set of coordinates and return a list of coordinates of it's neighbors. However, when it hits here:if result[i][0] < 0 or result[i][0] >= board.dimensions: result.pop(i) when i is 2, it gives me an out of index error. I can manage to have it print result[2][0] but at the if statement it throws the errors. I have no clue how this is happening and if anyone could shed any light on this problem I'd be forever in debt. def neighborGen(row,col,board): """ returns lists of coords of neighbors, in order of up, down, left, right """ result = [] result.append([row-1 , col]) result.append([row+1 , col]) result.append([row , col-1]) result.append([row , col+1]) #prune off invalid neighbors (such as (0,-1), etc etc) for i in range(len(result)): if result[i][0] < 0 or result[i][0] >= board.dimensions: result.pop(i) if result[i][1] < 0 or result[i][1] >= board.dimensions: result.pop(i) return result

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• socket.error: [Errno 10054]

  - by C0d3r

  import socket, sys if len(sys.argv) !=3 : print "Usage: ./supabot.py <host> <port>" sys.exit(1) irc = sys.argv[1] port = int(sys.argv[2]) sck = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sck.connect((irc, port)) sck.send('NICK supaBOT\r\n') sck.send('USER supaBOT supaBOT supaBOT :supaBOT Script\r\n') sck.send('JOIN #darkunderground' + '\r\n') data = '' while True: data = sck.recv(1024) if data.find('PING') != -1: sck.send('PONG ' + data.split() [1] + '\r\n') print data elif data.find('!info') != -1: sck.send('PRIVMSG #darkunderground supaBOT v1.0 by sourD' + '\r\n') print sck.recv(1024) when I run this code I get this error.. socket.error: [Errno 10054] An existing connection was forcibly closed by the remote host it says that the error is in line 16, in data = sck.recv(1024)

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• SQL Server 2000 - Filter by String Length

  - by user208662

  Hello, I have a database on a SQL Server 2000 server. This database has a table called "Person" that has a field call "FullName" that is a VARCHAR(100). I am trying to write a query that will allow me to get all records that have a name. Records that do not have a name have a FullName value of either null or an empty string. How do I get all of the Person records have a FullName? In other words, I want to ignore the records that do not have a FullName. Currently I am trying the following: SELECT * FROM Person p WHERE p.FullName IS NOT NULL AND LEN(p.FullName) > 0 Thank you

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• Lucene: Fastest way to return the document occurance of a phrase?

  - by dont say the kid's name

  Hi Guys, I am trying to use Lucene (actually PyLucene!) to find out how many documents contain my exact phrase. My code currently looks like this... but it runs rather slow. Does anyone know a faster way to return document counts? phraseList = ["some phrase 1", "some phrase 2"] #etc, a list of phrases... countsearcher = IndexSearcher(SimpleFSDirectory(File(STORE_DIR)), True) analyzer = StandardAnalyzer(Version.LUCENE_CURRENT) for phrase in phraseList: query = QueryParser(Version.LUCENE_CURRENT, "contents", analyzer).parse("\"" + phrase + "\"") scoreDocs = countsearcher.search(query, 200).scoreDocs print "count is: " + str(len(scoreDocs))

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• Python code, extracting extensions

  - by user1434001

  import os path = '/Users/Marjan/Documents/Nothing/Costco' print path names = os.listdir(path) print len(names) for name in names: print name Here is the code I've been using, it lists all the names in this category in terminal. There are a few filenames in this file (Costco) that don't have .html and _files. I need to pick them out, the only issue is that it has over 2,500 filenames. Need help on a code that will search through this path and pick out all the filenames that don't end with .html or _files. Thanks guys

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• Python: Access members of a set

  - by emu

  Say I have a set myset of custom objects that may be equal although their references are different (a == b and a is not b). Now if I add(a) to the set, Python correctly assumes that a in myset and b in myset even though there is only len(myset) == 1 object in the set. That is clear. But is it now possible to extract the value of a somehow out from the set, using b only? Suppose that the objects are mutable and I want to change them both, having forgotten the direct reference to a. Put differently, I am looking for the myset[b] operation, which would return exactly the member a of the set. It seems to me that the type set cannot do this (faster than iterating through all its members). If so, is there at least an effective work-around?

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