What does the '.' (dot or period) in a Go import statement do?

In the Go tutorial, and most of the Go code I've looked at, packages are imported like this:

import (
    "fmt"
    "os"
    "launchpad.net/lpad"
    ...
)

But in http://bazaar.launchpad.net/~niemeyer/lpad/trunk/view/head:/session_test.go, the gocheck package is imported with a . (period):

import (
    "http"
    . "launchpad.net/gocheck"
    "launchpad.net/lpad"
    "os"    
)

What is the significance of the . (period)?

Solution 1:

It allows the identifiers in the imported package to be referred to in the local file block without a qualifier.

If an explicit period (.) appears instead of a name, all the package's exported identifiers will be declared in the current file's file block and can be accessed without a qualifier.

Assume we have compiled a package containing the package clause package math, which exports function Sin, and installed the compiled package in the file identified by "lib/math". This table illustrates how Sin may be accessed in files that import the package after the various types of import declaration.

Import declaration          Local name of Sin

import   "lib/math"         math.Sin
import M "lib/math"         M.Sin
import . "lib/math"         Sin

Ref: http://golang.org/doc/go_spec.html#Import_declarations

Solution 2:

Here's an analogy for those coming from Python:

• Go's import "os" is roughly equivalent to Python's import os
• Go's import . "os" is roughly equivalent to Python's from os import *

In both languages, using the latter is generally frowned upon but there can be good reasons for doing it.