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
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