itertools

问题 I am trying to generate an array of all combinations of an arbitrary number of arrays. From the generated array, I would like to add an constraint that the sum of the numbers must lie between two bounds (say 'lower' and 'upper') One method of doing this is to use cartersian, sum the elements, and select the ones that fall within the lower and upper bounds. However, the main limitation is that it is possible to run out of memory given a large number of input arrays. Another method is to use

问题 I want to make a combination of 1's and 0's in a 2d array like the following: [[ 1, 1, 1, 1, 0, 0, 0, 0 ], [ 1, 1, 1, 0, 1, 0, 0, 0 ], [ 1, 1, 1, 0, 0, 1, 0, 0 ], [ 1, 1, 1, 0, 0, 0, 1, 0 ], [ 1, 1, 1, 0, 0, 0, 0, 1 ], . . . ] That means a combination of four 1's and four 0's. I have looked at the itertools module's permutations() and combinations() , but couldn't find any suitable functions to perform this combination. 回答1: You can also use combinations to generate unique combinations

问题 I mam trying to group the following details list: details = [('20130325','B'), ('20130320','A'), ('20130325','B'), ('20130320','A')] >>for k,v in itertools.groupby(details,key=operator.itemgetter(0)): >> print k,list(v) And this is the output with the above groupby statement: 20130325 [('20130325', 'B')] 20130320 [('20130320', 'A')] 20130325 [('20130325', 'B')] 20130320 [('20130320', 'A')] But my expected output was: 20130325 [('20130325', 'B'),('20130325', 'B')] 20130320 [('20130320', 'A'),(

问题 Let's say I have a pandas DataFrame with a certain number of columns and rows. What I want to do is to find the combination of 5 rows that combined yield the highest score in a particular column given some threshold. Below is a little toy example to illustrate it better: Below is a simplified example of my code, and I am wondering if this "brute force" approach is a smart way to tackle this problem. Is there any chance to do it more efficiently? Using other Python libraries, or are there

问题 In Python I am using the itertools.product() function to generate input parameters for a simulation. I have a test function that requires 4 input parameters a1, a2, b1 and b2. I use the following code generate the parameters. Example: params = itertools.product(range(10,41,2), range(10,41,2), range(0, 2), range(5, 31, 5)) … which gives me 3072 combinations. Unfortunately some combinations logically make no sense. E. g. if a2 is larger than a1 the test results are useless, also when b1 equals

问题 I have often used itertools module in Python but it feels like cheating if I don't know the logic behind it. Here is the code to find combinations of string when order is not important. def combinations(iterable, r): # combinations('ABCD', 2) --> AB AC AD BC BD CD # combinations(range(4), 3) --> 012 013 023 123 pool = tuple(iterable) n = len(pool) if r > n: return indices = list(range(r)) yield tuple(pool[i] for i in indices) while True: for i in reversed(range(r)): if indices[i] != i + n - r

问题 Is there a built-in function that works like zip(), but fills the results so that the length of the resulting list is the length of the longest input and fills the list from the left with e.g. None ? There is already an answer using zip_longest from itertools module and the corresponding question is very similar to this. But with zip_longest it seems that you can only fill missing data from the right. Here might be a use case for that, assuming we have names stored only like this (it's just

问题 I have this initial string. 'bananaappleorangestrawberryapplepear' And also have a tuple with strings: ('apple', 'plepe', 'leoran', 'lemon') I want a function so that from the initial string and the tuple with strings I obtain this: 'bananaxxxxxxxxxgestrawberryxxxxxxxar' I know how to do it imperatively by finding the word in the initial string for every word and then loop character by character in all initial string with replaced words. But it's not very efficient and ugly. I suspect there

问题 I'm creating a list with itertools from a list of ranges, so far I have this: start_list = [xrange(0,201,1),xrange(0,201,2),xrange(0,201,5),xrange(0,201,10),xrange(0,201,20),xrange(0,201,50),xrange(0,201,100),xrange(0,201,200)] Now, I know that if I were to try to run this next line it will kill my python interpreter: next_list = list(itertools.product(*start_list)) What I'm wondering is would it be possible to put in an argument that checks each tuple, for a sum of its items and only puts

问题 Given two numbers r and s , I would like to get a list of all permutations of n +-r and m +-s . For example (with r=3.14 and s=2.71 ), n = 1 m = 1 out = [ (+r, +s), (+r, -s), (-r, +s), (-r, -s), (+s, +r), (+s, -r), (-s, +r), (-s, -r) ] n = 1 m = 2 out = [ (+r, +s, +s), (+r, -s, +s), (-r, +s, +s), (-r, -s, +s), ... (+s, +r, +s), (-s, +r, +s), (+s, -r, +s), (-s, -r, +s), ... ... ] With itertools.product([+r, -r], repeat=n) I can get the list of the r s and s s separately, and I'd only need to