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
+9.1k Golang : Convert file content to Hex
+4.8k Unix/Linux : How to open tar.gz file ?
+15k Golang : Execute terminal command to remote machine example
+18.2k Golang : Compare floating-point numbers
+30.5k Golang : Copy directory - including sub-directories and files
+14.1k Golang : Get query string value on a POST request
+17.7k Golang : Calculate entire request body length during run time
+4.4k Golang : Return multiple values from function
+12.7k Golang : Fix cannot use buffer (type bytes.Buffer) as type io.Writer(Write method has pointer receiver) error
+22.2k Golang : Print out struct values in string format
+7k Golang : Qt splash screen with delay example
+9.1k Golang : Text file editor (accept input from screen and save to file)