what can i do/build with python code example

Example 1: when should I use a DIRECTORY_SEPARATOR vs a slash

It doesn't matter -- PHP's IO functions will internally convert 
slashes to the appropriate character.

Example 2: when do we need & in golang

var a = 5
var p = &a // p holds variable a's memory address
fmt.Printf("Address of var a: %p\n", p)
fmt.Printf("Value of var a: %v\n", *p)

// Let's change a value (using the initial variable or the pointer)
*p = 3 // using pointer
a = 3 // using initial var

fmt.Printf("Address of var a: %p\n", p)
fmt.Printf("Value of var a: %v\n", *p)