Golang : Extract or copy items from map based on value
Problem:
You want to copy map or make a new map with subset or extract items from another map based on certain value. For example, only copy values higher than 200.00 or with string values that match a slice's elements. Kinda like SQL select statement based on certain criteria.
Solution:
The code example below should be self explanatory.
package main
import "fmt"
func main() {
stockPrices := map[string]float32{
"IBM": 85.23,
"HPQ": 399.00,
"AAPL": 712.00,
"MSFT": 123.00,
}
fmt.Println("---------------------------------------------------------------------------")
fmt.Println("Original map content")
fmt.Println("---------------------------------------------------------------------------")
for k, v := range stockPrices {
fmt.Printf("key : %v, value : %v \n", k, v)
}
fmt.Println("---------------------------------------------------------------------------")
fmt.Println("New map subset with prices higher than 200")
fmt.Println("---------------------------------------------------------------------------")
higherStockPrices := map[string]float32{}
// copy map value with prices higher than 200
// to new map
for name, price := range stockPrices {
if price > 200.00 {
fmt.Println(name, price)
higherStockPrices[name] = price
}
}
//fmt.Println(higherStockPrices)
for higherName, higherPrice := range higherStockPrices {
fmt.Printf("key : %v , value : %v \n", higherName, higherPrice)
}
fmt.Println("---------------------------------------------------------------------------")
fmt.Println("New map subset with stock names that are found in slice")
fmt.Println("---------------------------------------------------------------------------")
stockNames := []string{"HPQ", "MSFT"}
for name, price := range stockPrices {
for _, sName := range stockNames {
if name == sName {
fmt.Println(name, price)
}
}
}
}
Output :
-------------------------------------------------------------------------------
Original map content
-------------------------------------------------------------------------------
key : IBM, value : 85.23
key : HPQ, value : 399
key : AAPL, value : 712
key : MSFT, value : 123
-------------------------------------------------------------------------------
New map subset with prices higher than 200
-------------------------------------------------------------------------------
HPQ 399
AAPL 712
key : HPQ , value : 399
key : AAPL , value : 712
-------------------------------------------------------------------------------
New map subset with stock names that are found in slice
-------------------------------------------------------------------------------
HPQ 399
MSFT 123
References:
See also : Golang : How to delete element(data) from map ?
By Adam Ng
IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.
Advertisement
Tutorials
+23.7k Golang : Find biggest/largest number in array
+13.1k Facebook PHP getUser() returns 0
+13.2k Golang : Get user input until a command or receive a word to stop
+4.3k Javascript : Access JSON data example
+21.7k Golang : Convert seconds to minutes and remainder seconds
+13.3k Golang : Set image canvas or background to transparent
+36k Golang : Convert date or time stamp from string to time.Time type
+5.2k Golang : Display advertisement images or strings on random order
+19.3k Golang : Set or Add HTTP Request Headers
+18.8k Golang : Calculate entire request body length during run time
+10.3k Golang : Bubble sort example
+11k Golang : Fix fmt.Scanf() on Windows will scan input twice problem