How do you use the ellipsis slicing syntax in Python?
This came up in Hidden features of Python, but I can’t see good documentation or examples that explain how the feature works. 4 Answers 4
slice
How to join a slice of strings into a single string?
package main import ( “fmt” “strings” ) func main() { reg := […]string {“a”,”b”,”c”} fmt.Println(strings.Join(reg,”,”)) } gives me an error of: prog.go:10: cannot use reg (type [3]string) as type []string in argument to strings.Join Is there a more direct/better way than looping and adding to a var? 3 Answers 3
How to get the last element of a slice?
What is the Go way for extracting the last element of a slice? var slice []int slice = append(slice, 2) slice = append(slice, 7) slice[len(slice)-1:][0] // Retrieves the last element The solution above works, but seems awkward. 5 Answers 5
How to slice an array in Bash
Looking the “Array” section in the bash(1) man page, I didn’t find a way to slice an array. So I came up with this overly complicated function: #!/bin/bash # @brief: slice a bash array # @arg1: output-name # @arg2: input-name # @args: seq args # ———————————————- function slice() { local output=$1 local input=$2 shift 2 … Read more
Explanation of [].slice.call in javascript?
I stumbled onto this neat shortcut for converting a DOM NodeList into a regular array, but I must admit, I don’t completely understand how it works: [].slice.call(document.querySelectorAll(‘a’), 0) So it starts with an empty array [], then slice is used to convert the result of call to a new array yeah? The bit I don’t … Read more
How to delete an element from a Slice in Golang
fmt.Println(“Enter position to delete::”) fmt.Scanln(&pos) new_arr := make([]int, (len(arr) – 1)) k := 0 for i := 0; i < (len(arr) – 1); { if i != pos { new_arr[i] = arr[k] k++ i++ } else { k++ } } for i := 0; i < (len(arr) – 1); i++ { fmt.Println(new_arr[i]) } I am … Read more
Select rows in pandas MultiIndex DataFrame
What are the most common pandas ways to select/filter rows of a dataframe whose index is a MultiIndex? Slicing based on a single value/label Slicing based on multiple labels from one or more levels Filtering on boolean conditions and expressions Which methods are applicable in what circumstances Assumptions for simplicity: input dataframe does not have … Read more
ValueError: setting an array element with a sequence
This Python code: import numpy as p def firstfunction(): UnFilteredDuringExSummaryOfMeansArray = [] MeanOutputHeader=[‘TestID’,’ConditionName’,’FilterType’,’RRMean’,’HRMean’, ‘dZdtMaxVoltageMean’,’BZMean’,’ZXMean’,’LVETMean’,’Z0Mean’, ‘StrokeVolumeMean’,’CardiacOutputMean’,’VelocityIndexMean’] dataMatrix = BeatByBeatMatrixOfMatrices[column] roughTrimmedMatrix = p.array(dataMatrix[1:,1:17]) trimmedMatrix = p.array(roughTrimmedMatrix,dtype=p.float64) #ERROR THROWN HERE myMeans = p.mean(trimmedMatrix,axis=0,dtype=p.float64) conditionMeansArray = [TestID,testCondition,’UnfilteredBefore’,myMeans[3], myMeans[4], myMeans[6], myMeans[9], myMeans[10], myMeans[11], myMeans[12], myMeans[13], myMeans[14], myMeans[15]] UnFilteredDuringExSummaryOfMeansArray.append(conditionMeansArray) secondfunction(UnFilteredDuringExSummaryOfMeansArray) return def secondfunction(UnFilteredDuringExSummaryOfMeansArray): RRDuringArray = p.array(UnFilteredDuringExSummaryOfMeansArray,dtype=p.float64)[1:,3] return firstfunction() Throws this error … Read more
How to take column-slices of dataframe in pandas
I load some machine learning data from a CSV file. The first 2 columns are observations and the remaining columns are features. Currently, I do the following: data = pandas.read_csv(‘mydata.csv’) which gives something like: data = pandas.DataFrame(np.random.rand(10,5), columns = list(‘abcde’)) I’d like to slice this dataframe in two dataframes: one containing the columns a and … Read more
Correct way to initialize empty slice
To declare an empty slice, with a non-fixed size, is it better to do: mySlice1 := make([]int, 0) or: mySlice2 := []int{} Just wondering which one is the correct way. 5 Answers 5
