slice

Is there a way to check slices/maps for the presence of a value? I would like to add a value to a slice only if it does not exist in the slice. This works, but it seems verbose. Is there a beter way to do this? orgSlice := []int{1, 2, 3} newSlice := []int{} newInt := 2 newSlice = append(newSlice, newInt) for _, v := range orgSlice { if v != newInt { newSlice = append(newSlice, v) } } newSlice == [2 1 3] Your approach would take linear time for each insertion. A better way would be to use a map[int]struct{} . Alternatively, you could also use a map[int]bool or something similar, but the empty

So I just came across what seems to me like a strange Python feature and wanted some clarification about it. The following array manipulation somewhat makes sense: p = [1,2,3] p[3:] = [4] p = [1,2,3,4] I imagine it is actually just appending this value to the end, correct? Why can I do this, however? p[20:22] = [5,6] p = [1,2,3,4,5,6] And even more so this: p[20:100] = [7,8] p = [1,2,3,4,5,6,7,8] This just seems like wrong logic. It seems like this should throw an error! Any explanation? -Is it just a weird thing Python does? -Is there a purpose to it? -Or am I thinking about this the wrong

Is there anything similar to a slice.contains(object) method in Go without having to do a search through each element in a slice? Mostafa has already pointed out that such a method is trivial to write, and mkb gave you a hint to use the binary search from the sort package. But if you are going to do a lot of such contains checks, you might also consider using a map instead. It's trivial to check if a specific map key exists by using the value, ok := yourmap[key] idiom. Since you aren't interested in the value, you might also create a map[string]struct{} for example. Using an empty struct{}

As I only now noticed after commenting on this answer , slices in Python 3 return shallow copies of whatever they're slicing rather than views. Why is this still the case? Even leaving aside numpy's usage of views rather than copies for slicing, the fact that dict.keys , dict.values , and dict.items all return views in Python 3, and that there are many other aspects of Python 3 geared towards greater use of iterators, makes it seem that there would have been a movement towards slices becoming similar. itertools does have an islice function that makes iterative slices, but that's more limited

I am trying to print the last part of a string before a certain character. I'm not quite sure whether to use the string .split() method or string slicing or maybe something else. Here is some code that doesn't work but I think shows the logic: x = 'http://test.com/lalala-134' print x['-':0] # beginning at the end of the string, return everything before '-' Note that the number at the end will vary in size so I can't set an exact count from the end of the string. You are looking for str.rsplit() , with a limit: print x.rsplit('-', 1)[0] .rsplit() searches for the splitting string from the end

There is some inconvenience while processing JSON response from a web server. For example, I don't know the data structure (and don't want to model it) of the JSON in advance, and just want to get the value from it! So, for Python, I can just write value = response["body"][4]["data"]["uid"] //response is a dictionary But for Golang, I need to do the assertion for every element! value := response["body"].([]interface{})[4].(map[string]interface{})["data"].(map[string]interface{})["uid"] //response is a map[string]interface{} This is what I write in golang to get the value I need. Do you have

This question already has an answer here: Understanding slice notation 32 answers I'm a bit confused about slicing a list and the numbering here. Python tends to start from 0 instead of 1, and it's shown below to work in that way well enough. But if we're starting from 0, and going until 3, why am I not getting exam instead of exa ? After all, 0 - 3 is 4 numbers. >>> test = "example string" >>> print test[:3] exa >>> print test[0:3] exa >>> print test[1:3] xa This is an intentional way, last element is exclusive. Why is it so? Firstly, my understanding it is because test[0:len(test)] should

I need to make a copy of a slice in Go and reading the docs there is a copy function at my disposal. The copy built-in function copies elements from a source slice into a destination slice. (As a special case, it also will copy bytes from a string to a slice of bytes.) The source and destination may overlap. Copy returns the number of elements copied, which will be the minimum of len(src) and len(dst). But when I do: arr := []int{1, 2, 3} tmp := []int{} copy(tmp, arr) fmt.Println(tmp) fmt.Println(arr) My tmp is empty as it was before (I even tried to use arr, tmp ): [] [1 2 3] You can check it