cartesian-product

问题 I'm trying to get the Cartesian product of multiple arrays but the arrays are pretty large and I am trying to optimize memory usage. I have tried implementing a generator by using the below code but it just returns that there is a generator at a certain location. import itertools x = [[1,2],[3,4]] def iter_tools(*array): yield list(itertools.product(*array)) print(iter_tools(*x)) When I try the same code but with return instead of yield it works fine. How could I get the cartesian product by

问题 I'm am trying to get all possible combinations of 11 values repeated 80 times but filter out cases where the sum is above 1. The code below achieves what I'm trying to do but takes days to run: import numpy as np import itertools unique_values = np.linspace(0.0, 1.0, 11) lst = [] for p in itertools.product(unique_values , repeat=80): if sum(p)<=1: lst.append(p) The solution above would work but needs way too much time. Also, in this case I would have to periodically save the 'lst' into the

问题 I have the following table: create table #table ( time int, key char(1), val int ) with the following data: insert into #table (time, key, val) values (0,"a",1) insert into #table (time, key, val) values (0,"b",2) insert into #table (time, key, val) values (1,"a",10) insert into #table (time, key, val) values (2,"b",20) and I would like to come up with a join of that will yield the following rows/cols: 0 a 1 0 b 2 1 a 10 1 b 0 2 a 0 2 b 20 Which is basically the cartesian product of the

问题 I have the following table: create table #table ( time int, key char(1), val int ) with the following data: insert into #table (time, key, val) values (0,"a",1) insert into #table (time, key, val) values (0,"b",2) insert into #table (time, key, val) values (1,"a",10) insert into #table (time, key, val) values (2,"b",20) and I would like to come up with a join of that will yield the following rows/cols: 0 a 1 0 b 2 1 a 10 1 b 0 2 a 0 2 b 20 Which is basically the cartesian product of the

问题 I am not able to understand how Cartesian product works. Consider the simple schema: mysql> select * from account; +----------------+-------------+---------+ | account_number | branch_name | balance | +----------------+-------------+---------+ | A101 | Downtown | 500 | | A102 | Perryridge | 400 | | A201 | Brighton | 900 | | A215 | Mianus | 700 | | A217 | Brighton | 750 | | A222 | Redwood | 700 | | A305 | Round Hill | 350 | +----------------+-------------+---------+ 7 rows in set (0.00 sec)

问题 So I'm looking at different ways to compute the Cartesian product of n arrays, and I came across the rather elegant solution (here on SO) of using the following code: import itertools for array in itertools.product(*arrays): print array Looking at the python doc page (I'm using 2.7, btw) for itertools.product() , it says the code is equivalent to the following: def product(*args, **kwds): # product('ABCD', 'xy') --> Ax Ay Bx By Cx Cy Dx Dy # product(range(2), repeat=3) --> 000 001 010 011 100

问题 I’m in need of some help and guidance on the design of my code. I want to run tests with multiple variables set to multiple values, without creating insane amounts of nested loops. I got a struct which holds various variables like this (only three integers as an example, but the real deal will hold a lot more, including booleans, doubles etc): struct VarHolder { int a; int b; int c; // etc.. // etc.. }; The struct get passed into a test function. bool TestFunction(const VarHolder& _varholder)

问题 While writing in SQL, how would I know if I should use cross product (cross join, Cartesian product) or natural join? 回答1: CROSS JOIN creates all possible pairings of rows from two tables, whether they match or not. You don't use any join condition for a cross product, because the condition would always be true for any pairing. An example of using CROSS JOIN : you have tables of ShoeColors and ShoeSizes, and you want to know how many possible combinations there are. SELECT COUNT(*) FROM

来源： https://stackoverflow.com/questions/61678496/how-to-join-strings-from-a-cartesian-product-of-two-lists

来源： https://stackoverflow.com/questions/61678496/how-to-join-strings-from-a-cartesian-product-of-two-lists