Definition General array slicing can be implemented (whether or not built into the language) by referencing every array through a dope vector or descriptor — a record that contains the address of the first array element, and then the range of each index and the corresponding coefficient in the indexing formula. This technique also allows … Read more
Everything in Go is passed by value. And a copy is made of the passed value. Test3.combo() has value (non-pointer) receiver: func (c Test3) run() []int { c.combo() return c.all } func (c Test3) combo() { for i := 0; i < 2; i++ { c.all = append(c.all, i) fmt.Println(“Test3 step”, i + 1, c.all) … Read more
The syntax is always [start:end:step] so if you go backwards your start needs to be greater than the end. Also remember that it includes start and excludes end, so you need to subtract 1 after you swap start and end. l[5:2:-1]= [6, 5, 4] l[4:1:-1]= [5, 4, 3]
I think you need numpy.r_ for concanecate positions of columns, then use iloc for selecting: print (df.iloc[:, np.r_[1:3, 6:len(df.columns)]]) and for second approach subset by list: print (df[years_month]) Sample: df = pd.DataFrame({‘2000-1’:[1,3,5], ‘2000-2’:[5,3,6], ‘2000-3’:[7,8,9], ‘2000-4’:[1,3,5], ‘2000-5’:[5,3,6], ‘2000-6’:[7,8,9], ‘2000-7’:[1,3,5], ‘2000-8’:[5,3,6], ‘2000-9’:[7,4,3], ‘A’:[1,2,3], ‘B’:[4,5,6], ‘C’:[7,8,9]}) print (df) 2000-1 2000-2 2000-3 2000-4 2000-5 2000-6 2000-7 2000-8 2000-9 A … Read more
Here’s a vectorized approach – def slicer_vectorized(a,start,end): b = a.view((str,1)).reshape(len(a),-1)[:,start:end] return np.fromstring(b.tostring(),dtype=(str,end-start)) Sample run – In [68]: a = np.array([‘hello’, ‘how’, ‘are’, ‘you’]) In [69]: slicer_vectorized(a,1,3) Out[69]: array([‘el’, ‘ow’, ‘re’, ‘ou’], dtype=”|S2″) In [70]: slicer_vectorized(a,0,3) Out[70]: array([‘hel’, ‘how’, ‘are’, ‘you’], dtype=”|S3″) Runtime test – Testing out all the approaches posted by other authors that I … Read more
Order matters If you want to keep your array ordered, you have to shift all of the elements at the right of the deleting index by one to the left. Hopefully, this can be done easily in Golang: func remove(slice []int, s int) []int { return append(slice[:s], slice[s+1:]…) } However, this is inefficient because you … Read more
This is an old question, but here’s my two cents. PeterSO’s answer is slightly more concise, but slightly less efficient. You already know how big it’s going to be so you don’t even need to use append: keys := make([]int, len(mymap)) i := 0 for k := range mymap { keys[i] = k i++ } … Read more
The standard library does not have a built-in function for reversing a slice. Use a for loop to reverse a slice: for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 { s[i], s[j] = s[j], s[i] } Use type parameters to write a generic reverse function in Go 1.18 or … Read more
Would this work? $result = array_map(function($arr) { return [ ‘id’ => $arr[‘id’], ‘name’ => $arr[‘name’] ]; }, $orig_array);