how to implement the python `zip` function in golang?
12,574
Solution 1
You could do something like this, where you give the tuple type a name:
package main
import "fmt"
type intTuple struct {
a, b int
}
func zip(a, b []int) ([]intTuple, error) {
if len(a) != len(b) {
return nil, fmt.Errorf("zip: arguments must be of same length")
}
r := make([]intTuple, len(a), len(a))
for i, e := range a {
r[i] = intTuple{e, b[i]}
}
return r, nil
}
func main() {
a := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 0}
b := []int{0, 9, 8, 7, 6, 5, 4, 3, 2, 1}
fmt.Println(zip(a, b))
}
Or alternatively use an unnamed type for the tuple, like this:
package main
import "fmt"
func zip(a, b []int) ([][3]int, error) {
if len(a) != len(b) {
return nil, fmt.Errorf("zip: arguments must be of same length")
}
r := make([][4]int, len(a), len(a))
for i, e := range a {
r[i] = [2]int{e, b[i]}
}
return r, nil
}
func main() {
a := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 0}
b := []int{0, 9, 8, 7, 6, 5, 4, 3, 2, 1}
fmt.Println(zip(a, b))
}
And finally here's a soft-generic way of doing it:
package main
import (
"fmt"
"reflect"
)
func zip(a, b, c interface{}) error {
ta, tb, tc := reflect.TypeOf(a), reflect.TypeOf(b), reflect.TypeOf(c)
if ta.Kind() != reflect.Slice || tb.Kind() != reflect.Slice || ta != tb {
return fmt.Errorf("zip: first two arguments must be slices of the same type")
}
if tc.Kind() != reflect.Ptr {
return fmt.Errorf("zip: third argument must be pointer to slice")
}
for tc.Kind() == reflect.Ptr {
tc = tc.Elem()
}
if tc.Kind() != reflect.Slice {
return fmt.Errorf("zip: third argument must be pointer to slice")
}
eta, _, etc := ta.Elem(), tb.Elem(), tc.Elem()
if etc.Kind() != reflect.Array || etc.Len() != 2 {
return fmt.Errorf("zip: third argument's elements must be an array of length 2")
}
if etc.Elem() != eta {
return fmt.Errorf("zip: third argument's elements must be an array of elements of the same type that the first two arguments are slices of")
}
va, vb, vc := reflect.ValueOf(a), reflect.ValueOf(b), reflect.ValueOf(c)
for vc.Kind() == reflect.Ptr {
vc = vc.Elem()
}
if va.Len() != vb.Len() {
return fmt.Errorf("zip: first two arguments must have same length")
}
for i := 0; i < va.Len(); i++ {
ea, eb := va.Index(i), vb.Index(i)
tt := reflect.New(etc).Elem()
tt.Index(0).Set(ea)
tt.Index(1).Set(eb)
vc.Set(reflect.Append(vc, tt))
}
return nil
}
func main() {
a := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 0}
b := []int{0, 9, 8, 7, 6, 5, 4, 3, 2, 1}
c := [][2]int{}
e := zip(a, b, &c)
if e != nil {
fmt.Println(e)
return
}
fmt.Println(c)
}
Solution 2
To zip
some number of slice []int
lists,
package main
import "fmt"
func zip(lists ...[]int) func() []int {
zip := make([]int, len(lists))
i := 0
return func() []int {
for j := range lists {
if i >= len(lists[j]) {
return nil
}
zip[j] = lists[j][i]
}
i++
return zip
}
}
func main() {
a := []int{1, 2, 3}
b := []int{4, 5, 6}
c := []int{7, 8, 9, 0}
iter := zip(a, b, c)
for tuple := iter(); tuple != nil; tuple = iter() {
fmt.Println("tuple:", tuple)
}
}
Output:
tuple: [1 4 7] tuple: [2 5 8] tuple: [3 6 9]
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Author by
holys
Updated on September 14, 2022Comments
-
holys about 1 year
Sometimes, it's convenient to combine two lists into a tuple using
zip
built-in function in Python. How to make this similarly in Go?For example:
>>> zip ([1,2],[3,4]) [(1,3), (2,4)]
-
blackgreen over 1 yearExample with generics below
-