This post is a text version of the code samples and resources from Golang for Python Devs by Dana Garifullina from Kiwi PyCon 2016.
Some resources no longer work, so I’ve updated to the most accurate thing I can find.
Some Python samples were Python 2, updated to Python 3.
Most code OCR’d, may contain translation issues
Hello World
Python
print("Hello World!")
Golang
package main
import "fmt"
func main() {
fmt.Println("Hello, KiwiPycon!")
}
Lists
Python
# initialise a list
arr = []
# initialise sized List
arr = [0]*12
# add one element
arr.append(20)
arr[0] = 21
# Length of list
len(arr) # 13
# List extending
arr.extend([4, 5, 6])
# get element by index
arr[2] # 0
Golang
func main() {
// initialise a list
var arr [3]int // ［9, e, 9］
// change element via index
arr[0] = 125
// SLICES - when you don't know size
// of List
colours := []string{"red", "blue"}
// append == recreation
colours = append(colours, "purple")
// Length, capacity
fmt.Println(len(colours))
fmt.Println(cap(colours))
}
Dictionaries (maps)
Python
#initialisation of dictionary
py_map = {}
# add element
py_map["first_key"] = 25
# delete element
py_map.pop("first_key")
# re-fill
py_map = {"first_key": 26}
# print element
if "first_key" in py_map:
print(py_map["first_key"])
# or just
print(py_map.get("first_key"))
Golang
func main() {
// initialisation
go_map := make(map[string]int)
go_map["first_key"] = 25
fmt.Println(go_map["first_key"])
// remove by key
delete(go_map, "first_key")
// print element
if element, ok := go_map["random_key"]; ok {
fmt.Println(element) // won't be printed
}
if element, ok := go_map["first_key"]; ok {
fmt.Println(element) // 25
}
}
While Loop
Python
# while Loop
i = 1
while i <= 10:
print(i)
i += 1
Golang
func main() {
// Loop from 0 until 10 is reached.
for i := 1; i <= 10; i++ {
// Display integer.
fmt.Println(i)
}
}
Infinite Loop
Python
# no condition
id = 10
while True:
if id > 20:
break
print(id)
id +=5
Golang
func main() {
id := 10
// This Loop continues infinitely until broken.
for {
// Break if id is past a certain number.
if id > 20 {
break
}
fmt.Println(id)
id += 5
}
}
Range Loop
Python
#for Loop
for i in range (0, 25):
print(i)
# other way
names = ["Peter", "Anders", "Bengt"]
for i, name in enumerate (names):
print("%d. %s" % (i + 1, name))
Golang
func main() {
names := []string{
"Peter",
"Anders",
"Bengt",
}
/* This will print
1. Peter
2. Anders
3. Bengt
*/
for i, name := range names {
fmt.Printf("%d. %s\n", i+1, name)
}
}
If Statements
Python
# if-elif-else switches
value = 1.0
if value == 1.0:
print("This is 1.0 but I will print...")
value = value + 0.5
if value == 1.5:
print("One point five")
elif value == 2.5:
print("Two point five")
else:
print("Anything else")
Golang
func main() {
value := 1.0
// Switch on a floating-point value.
switch value {
case 1.0:
fmt.Println("This is 1.0, but i will print...")
fallthrough
case 1.5:
fmt.Println("One point five")
case 2.5:
fmt.Println("Two point five")
default:
fmt.Println("Anything else")
}
}
Exceptions
Python
try:
# An error occurs.
x = 1 / 0
except:
# Except clause:
print("Error encountered")
finally:
# Finally clause:
print("Finally clause reached")
# another example
while True:
# Read int from console.
denominator = int(input())
# Use int as denominator.
try:
i = 1 / denominator
except:
print("Error")
else:
print("OK")
Error handling
Golang
func explode() {
// Cause a panic.
panic("WRONG")
}
func main() {
// Handle errors in defer func with recover.
defer func() {
if err := recover(); err != nil {
// Handle our error.
fmt.Println("FIX")
fmt.Println(" ERR", err)
}
}()
// This causes an error.
explode()
}
Open (name string) (file *File, err error)
f, err := os.Open("filename.ext")
if err != nil {
log. Fatal(err)
}
// do something with the open *File f
OOP in Go
package main
import "fmt"
type Attendee struct {
Topic string
Person Person
}
type Person struct {
Name string
City string
Company string
}
func (a Attendee) SayHi() {
fmt.Printf("Hi, my name is %s and today I will talk about %s! \n", a.Person.Name, a.Topic)
}
func (a Attendee) About() {
fmt.Printf("I'm from %s and currently working in %s by the way. \n", a.Person.City, a.Person.Company)
}
func main() {
guy := Attendee{
Topic: "Meetings with cookies: never have less then 10",
Person: Person{
Name: "John Doe",
City: "Doeville",
Company: "WeCodes Inc",
},
}
guy.SayHi()
guy.About()
}
Empty Interfaces
package main
import (
"fmt"
"strconv" // for conversions to and from string
)
type Person struct {
name string
age int
phone string
}
// Returns a nice string representing a Person
// With this method, Person implements fmt.Stringer
func (p Person) String() string {
return "<<" + p.name + " - " + strconv.Itoa(p.age) + " years - @" + p.phone + ">>"
}
func main() {
John := Person{"John", 29, "022-4XX-66X"}
fmt.Println("This Person is: ", John)
}
Concurrency
import (
"fmt"
"time"
)
func main() {
go sayHello()
fmt.Println("Going to sleep....ZZzzzzzZZ")
//make main last a little bit more
time.Sleep(6 * time.Second)
}
func sayHello() {
fmt.Println("Waking up....")
time.Sleep(3 * time.Second)
fmt.Println("Hello KiwiPycon!")
}
// Going to sleep...ZZzzzzzZZ
// Waking up....
// Hello KiwiPycon!
Channels and Defers
(complicated, see talk)
Resources
Books:
- http://www.golang-book.com/books/intro
- no longer works. Try https://github.com/ashleymcnamara/an-introduction-to-programming-in-go
- Introducing Go by Caleb Doxsey http://shop.oreilly.com/product/0636920046516.do
Official docs:
- A tour of Go: https://tour.golang.org/welcome/1
- Effective Go: https://golang.org/doc/effective_go.html
- Blog: https://blog.golang.org/
Talks:
- The Evolution of Go https://youtu.be/0ReKdcpNyQg
- Concurrency Is Not Parallelism https://youtu.be/cN_DpYBzKso
- Probably https://go.dev/blog/waza-talk
- Simplicity is complicated: https://youtu.be/rFejpH_tAHM
Articles:
- Traps, Gotchas, etc for New Golang Devs: http://goo.gl/ijZVrw
- http://devs.cloudimmunity.com/gotchas-and-common-mistakes-in-go-golang/
- Five things that make Go fast: http://goo.gl/WYPJ8K
- Probably https://dave.cheney.net/2014/06/07/five-things-that-make-go-fast