gen.py

import json
import random
import string

def rstr(N):
    return ''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(N))

data = {}

for i in range(100000):
    x = {}
    for j in range(10):
        x[rstr(10)] = rstr(100)
    data[str(i)] = x

with open('huge.json', 'w') as y:
    json.dump(data, y)

    

go.go

package main

import (
	"encoding/json"
	"fmt"
	"os"
	"time"
)

func main() {
	input, err := os.Open("huge.json")
	if err != nil {
		fmt.Printf("File error: %v\n", err)
		os.Exit(1)
	}

	var i interface{}

	before := time.Now()
	dec := json.NewDecoder(input)
	err = dec.Decode(&i)
	if err != nil {
		fmt.Printf("Encode error: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("LOAD: ", time.Since(before))

	output, err := os.Create("out.go.json")
	if err != nil {
		fmt.Printf("File error (write): %v\n", err)
		os.Exit(1)
	}

	before = time.Now()
	enc := json.NewEncoder(output)
	err = enc.Encode(i)
	if err != nil {
		fmt.Printf("Encode error: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("DUMP: ", time.Since(before))
}

interaction

bench$ for n in `seq 1 3`; do make go python > /dev/null; done
bench$ make go python
go build ./go.go
echo "Running go version."
Running go version.
./go
LOAD:  2.016554434s
DUMP:  1.478200338s
echo "Running python version"
Running python version
python py.py
LOAD elapsed=1.56545710564
DUMP elapsed=3.07746505737
bench$ go version
go version go1.9 darwin/amd64
agwozd-ltm2:bench agwozdziewycz$ python --version
Python 2.7.10
bench$ du -h *
114M    huge.json
112M    out.go.json
114M    out.py.json

Makefile

go:
	go build ./go.go
	echo "Running go version."
	./go

python:
	echo "Running python version"
	python py.py

.PHONY: go python

py.py

import json
import time

before = time.time()
with open('huge.json') as x:
    obj = json.load(x)
    print("LOAD elapsed={}".format(time.time() - before))

before = time.time()
with open('out.py.json', 'w') as y:
    json.dump(obj, y)
    print("DUMP elapsed={}".format(time.time() - before))