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  • undo or reverse argsort(), python

    - by Vincent
    Given an array 'a' I would like to sort the array by columns "a.sort(axis=0)" do some stuff to the array and then undo the sort. By that I don't mean re sort but basically reversing how each element was moved. I assume argsort() is what I need but it is not clear to me how to sort an array with the results of argsort() or more importantly apply the reverse/inverse of argsort() Here is a little more detail I have an array a, shape(a) = rXc I need to sort each column aargsort = a.argsort(axis=0) # May use this later aSort = a.sort(axis=0) now average each row aSortRM = asort.mean(axis=1) now replace each col in a row with the row mean. is there a better way than this aWithMeans = ones_like(a) for ind in range(r) # r = number of rows aWithMeans[ind]* aSortRM[ind] Now I need to undo the sort I did in the first step. ????

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  • good practice for string.partition in python

    - by user1544915
    some case i write code like these: a,temp,b = s.partition('-') i just need to pick the first and 3rd element. temp would never be used. is there a better way to do this? the common case is ,a better way to pick separted element to make a new list? for example i want to make a new list use old list 0,1,3,7 element code would be this: newlist = [oldlist[0],oldlist[1],oldlist[3],oldlist[7]] it's pretty ugly,isn't it?

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  • Python os.path.walk() method

    - by Aaron Moodie
    I'm currently using the walk method in a uni assignment. It's all working fine, but I was hoping that someone could explain something to me. in the example below, what is the a parameter used for on the myvisit method? >>> from os.path import walk >>> def myvisit(a, dir, files): ... print dir,": %d files"%len(files) >>> walk('/etc', myvisit, None) /etc : 193 files /etc/default : 12 files /etc/cron.d : 6 files /etc/rc.d : 6 files /etc/rc.d/rc0.d : 18 files /etc/rc.d/rc1.d : 27 files /etc/rc.d/rc2.d : 42 files /etc/rc.d/rc3.d : 17 files /etc/rc.d/rcS.d : 13 files

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  • Google App Engine: Difficulty with Users API (or maybe just a Python syntax problem)

    - by Rosarch
    I have a simple GAE app that includes a login/logout link. This app is running on the dev server at the moment. The base page handler gets the current user, and creates a login/logout url appropriately. It then puts this information into a _template_data dictionary, for convenience of subclasses. class BasePage(webapp.RequestHandler): _user = users.get_current_user() _login_logout_link = None if _user: _login_logout_link = users.create_logout_url('/') else: _login_logout_link = users.create_login_url('/') _template_data = {} _template_data['login_logout_link'] = _login_logout_link _template_data['user'] = _user def render(self, templateName, templateData): path = os.path.join(os.path.dirname(__file__), 'Static/Templates/%s.html' % templateName) self.response.out.write(template.render(path, templateData)) Here is one such subclass: class MainPage(BasePage): def get(self): self.render('start', self._template_data) The login/logout link is displayed fine, and going to the correct devserver login/logout page. However, it seems to have no effect - the server still seems to think the user is logged out. What am I doing wrong here?

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  • Python: Trouble with YACC

    - by Rosarch
    I'm parsing sentences like: "CS 2310 or equivalent experience" The desired output: [[("CS", 2310)], ["equivalent experience"]] YACC tokenizer symbols: tokens = [ 'DEPT_CODE', 'COURSE_NUMBER', 'OR_CONJ', 'MISC_TEXT', ] t_DEPT_CODE = r'[A-Z]{2,}' t_COURSE_NUMBER = r'[0-9]{4}' t_OR_CONJ = r'or' t_ignore = ' \t' terms = {'DEPT_CODE': t_DEPT_CODE, 'COURSE_NUMBER': t_COURSE_NUMBER, 'OR_CONJ': t_OR_CONJ} for name, regex in terms.items(): terms[name] = "^%s$" % regex def t_MISC_TEXT(t): r'\S+' for name, regex in terms.items(): # print "trying to match %s with regex %s" % (t.value, regex) if re.match(regex, t.value): t.type = name return t return t (MISC_TEXT is meant to match anything not caught by the other terms.) Some relevant rules from the parser: precedence = ( ('left', 'MISC_TEXT'), ) def p_statement_course_data(p): 'statement : course_data' p[0] = p[1] def p_course_data(p): 'course_data : course' p[0] = p[1] def p_course(p): 'course : DEPT_CODE COURSE_NUMBER' p[0] = make_course(p[1], int(p[2])) def p_or_phrase(p): 'or_phrase : statement OR_CONJ statement' p[0] = [[p[1]], [p[3]]] def p_misc_text(p): '''text_aggregate : MISC_TEXT MISC_TEXT | MISC_TEXT text_aggregate | text_aggregate MISC_TEXT ''' p[0] = "%s %s" % (p[0], [1]) def p_text_aggregate_statement(p): 'statement : text_aggregate' p[0] = p[1] Unfortunately, this fails: # works as it should >>> token_list("CS 2110 or equivalent experience") [LexToken(DEPT_CODE,'CS',1,0), LexToken(COURSE_NUMBER,'2110',1,3), LexToken(OR_CONJ,'or',1,8), LexToken(MISC_TEXT,'equivalent',1,11), LexToken(MISC_TEXT,'experience',1,22)] # fails. bummer. >>> parser.parse("CS 2110 or equivalent experience") Syntax error in input: LexToken(MISC_TEXT,'equivalent',1,11) What am I doing wrong? I don't fully understand how to set precedence rules. Also, this is my error function: def p_error(p): print "Syntax error in input: %s" % p Is there a way to see which rule the parser was trying when it failed? Or some other way to make the parser print which rules its trying?

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  • Python: Problems finding string in website source code

    - by j00niner
    I open a website with urlopen. I then put the website sourcecode into a variable like so source = website.read() When I just print the source it comes out formatted correctly, however when I try to iterate through each line each character is it's own line. for example when I just print it looks like this <HTML> title</html> When I do this for line in source: print line it looks like this < H T M L ... etc I need to find a string that starts with "var" and then print that entire line.

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  • Shell halts while looping and 'transforming' values in dictionary (Python 2.7.5)

    - by Gus
    I'm building a program that will sum digits in a given list in a recursive way. Say, if the source list has 10 elements, the second list will have 9, the third 8 and so on until the last list that will have only one element. This is done by adding the first element to the second, then the second to the third and so on. I'm stuck without feedback from the shell. It halts without throwing any errors, then in a couple of seconds the fan is spinning like crazy. I've read quite a few posts here and changed my approach, but I'm not sure that what have so far can produce the results I'm looking for. Thanks in advance: #--------------------------------------------------- #functions #--------------------------------------------------- #sum up pairs in a list def reduce(inputList): i = 0 while (i < len(inputList)): #ref to current and next item j = i + 1 #don't go for the last item if j != len(inputList): #new number eq current + next number newNumber = inputList[i] + inputList[j] if newNumber >= 10: #reduce newNumber to single digit newNumber = sum(map(int, str(newNumber))) #collect into temp list outputList.append(newNumber) i = i + 1 return outputList; #--------------------------------------------------- #program starts here #--------------------------------------------------- outputList = [] sourceList = [7, 3, 1, 2, 1, 4, 6] counter = len(sourceList) dict = {} dict[0] = sourceList print '-------------' print 'Level 0:', dict[0] for i in range(counter): j = i + 1 if j != counter: baseList = dict.get(i) #check function to understand what it does newList = reduce(baseList) #new key and value from previous/transformed value dict[j] = newList print 'Level %d: %s' % (j, dict[j])

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  • Python: Determine whether list of lists contains a defined sequence

    - by duhaime
    I have a list of sublists, and I want to see if any of the integer values from the first sublist plus one are contained in the second sublist. For all such values, I want to see if that value plus one is contained in the third sublist, and so on, proceeding in this fashion across all sublists. If there is a way of proceeding in this fashion from the first sublist to the last sublist, I wish to return True; otherwise I wish to return False. In other words, for each value in sublist one, for each "step" in a "walk" across all sublists read left to right, if that value + n (where n = number of steps taken) is contained in the current sublist, the function should return True; otherwise it should return False. (Sorry for the clumsy phrasing--I'm not sure how to clean up my language without using many more words.) Here's what I wrote. a = [ [1,3],[2,4],[3,5],[6],[7] ] def find_list_traversing_walk(l): for i in l[0]: index_position = 0 first_pass = 1 walking_current_path = 1 while walking_current_path == 1: if first_pass == 1: first_pass = 0 walking_value = i if walking_value+1 in l[index_position + 1]: index_position += 1 walking_value += 1 if index_position+1 == len(l): print "There is a walk across the sublists for initial value ", walking_value - index_position return True else: walking_current_path = 0 return False print find_list_traversing_walk(a) My question is: Have I overlooked something simple here, or will this function return True for all true positives and False for all true negatives? Are there easier ways to accomplish the intended task? I would be grateful for any feedback others can offer!

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  • Python 3: list atributes within a class object

    - by MadSc13ntist
    is there a way that if the following class is created; I can grab a list of attributes that exist. (this class is just an bland example, it is not my task at hand) class new_class(): def __init__(self, number): self.multi = int(number) * 2 self.str = str(number) a = new_class(2) print(', '.join(a.SOMETHING)) * the attempt is that "multi, str" will print. the point here is that if a class object has attributes added at different parts of a script that I can grab a quick listing of the attributes which are defined.

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  • Python Attributes and Inheritance

    - by user368186
    Say I have the folowing code: class Class1(object): def __init__(self): self.my_attr = 1 self.my_other_attr = 2 class Class2(Class1): def __init__(self): super(Class1,self).__init__() Why does Class2 not inherit the attributes of Class1?

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  • Python 2.7 creating a multidimensional list

    - by poop
    I don't know why I am having so much trouble creating a 3 dimensional list. I need the program to create an empty n by n list. So for n = 4: x = [[[],[],[],[]],[[],[],[],[]],[[],[],[],[]],[[],[],[],[]]] I've tried using: y = [n*[n*[]]] y = [[[]]* n for i in range(n)] Which both appear to be creating copies of a reference. I've also tried naieve application of the list builder with little success: y = [[[]* n for i in range(n)]* n for i in range(n)] y = [[[]* n for i in range(1)]* n for i in range(n)] I've also tried building up the array iteratively using loops, with no success. In my rapid flurry of attempts to not post something stupidly easy to SO, I came upon a solution: y = [] for i in range(0,n): y.append([[]*n for i in range(n)]) Is there an easier/ more intuitive way of doing this?

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  • Selecting dictionary items by key efficiently in Python

    - by user248237
    suppose I have a dictionary whose keys are strings. How can I efficiently make a new dictionary from that which contains only the keys present in some list? for example: # a dictionary mapping strings to stuff mydict = {'quux': ..., 'bar': ..., 'foo': ...} # list of keys to be selected from mydict keys_to_select = ['foo', 'bar', ...] The way I came up with is: filtered_mydict = [mydict[k] for k in mydict.keys() \ if k in keys_to_select] but I think this is highly inefficient because: (1) it requires enumerating the keys with keys(), (2) it requires looking up k in keys_to_select each time. at least one of these can be avoided, I would think. any ideas? I can use scipy/numpy too if needed.

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  • python and regular expression with unicode

    - by bsn
    I need to delete some unicode symbols from the string '?????? ??????? ???????????? ??????????' I know they exist here for sure. I try: re.sub('([\u064B-\u0652\u06D4\u0670\u0674\u06D5-\u06ED]+)', '', '?????? ??????? ???????????? ??????????') but it doesn't work. String stays the same. ant suggestion what i do wrong?

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  • How can i optimize this python code

    - by RandomVector
    def maxVote(nLabels): count = {} maxList = [] maxCount = 0 for nLabel in nLabels: if nLabel in count: count[nLabel] += 1 else: count[nLabel] = 1 #Check if the count is max if count[nLabel] > maxCount: maxCount = count[nLabel] maxList = [nLabel,] elif count[nLabel]==maxCount: maxList.append(nLabel) return random.choice(maxList) nLabels contains a list of integers. The above function returns the integer with highest frequency, if more than one have same frequency then a randomly selected integer from them is returned. E.g. maxVote([1,3,4,5,5,5,3,12,11]) is 5

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  • Search inside dynamic array in python

    - by user2091683
    I want to implement a code that loops inside an array that its size is set by the user that means that the size isn't constant. for example: A=[1,2,3,4,5] then I want the output to be like this: [1],[2],[3],[4],[5] [1,2],[1,3],[1,4],[1,5] [2,3],[2,4],[2,5] [3,4],[3,5] [4,5] [1,2,3],[1,2,4],[1,2,5] [1,3,4],[1,3,5] and so on [1,2,3,4],[1,2,3,5] [2,3,4,5] [1,2,3,4,5] Can you help me implement this code?

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