Vim 插件是一个 .vim 的脚本文件,定义了函数、映射、语法规则和命令,可用于操作窗口、缓冲以及行。一般一个插件包含了命令定义和事件钩子。当使用 Python 编写 vim 插件时,函数外面是使用 VimL 编写,尽管 VimL 学起来很快,但 Python 更加灵活,例如可以用 urllib/httplib/simplejson 来访问某些 Web 服务,这也是为什么很多需要访问 Web 服务的插件都是使用 VimL + Python 编写的原因。
在开始编写插件之前,你需要确认 Vim 支持 Python,通过以下命令来判别:
接下来我们通过一个简单的例子来学习用 Python 编写 Vim 插件,该插件用来获取 Reddit 首页信息并显示在当前缓冲区上。
首先在 Vim 新建 vimmit.vim 文件,我们首先需要判断是否支持 Python,如果不支持给出提示信息:
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if !has( 'python' )
echo "Error: Required vim compiled with +python"
finish
endif
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上面这段代码就是用 VimL 编写的,它将检查 Vim 是否支持 Python。
下面是用 Python 编写的 Reddit() 主函数:
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" Vim comments start with a double quote.
" Function definition is VimL. We can mix VimL and Python in
" function definition.
function! Reddit()
" We start the python code like the next line.
python << EOF
# the vim module contains everything we need to interface with vim from
# python. We need urllib2 for the web service consumer.
import vim, urllib2
# we need json for parsing the response
import json
# we define a timeout that we'll use in the API call. We don't want
# users to wait much.
TIMEOUT = 20
URL = "http://reddit.com/.json"
try :
# Get the posts and parse the json response
response = urllib2.urlopen(URL, None , TIMEOUT).read()
json_response = json.loads(response)
posts = json_response.get( "data" , " ").get(" children ", " ")
# vim.current.buffer is the current buffer. It's list-like object.
# each line is an item in the list. We can loop through them delete
# them, alter them etc.
# Here we delete all lines in the current buffer
del vim.current. buffer [:]
# Here we append some lines above. Aesthetics.
vim.current. buffer [ 0 ] = 80 * "-"
for post in posts:
# In the next few lines, we get the post details
post_data = post.get( "data" , {})
up = post_data.get( "ups" , 0 )
down = post_data.get( "downs" , 0 )
title = post_data.get( "title" , "NO TITLE" ).encode( "utf-8" )
score = post_data.get( "score" , 0 )
permalink = post_data.get( "permalink" ).encode( "utf-8" )
url = post_data.get( "url" ).encode( "utf-8" )
comments = post_data.get( "num_comments" )
# And here we append line by line to the buffer.
# First the upvotes
vim.current. buffer .append( "↑ %s" % up)
# Then the title and the url
vim.current. buffer .append( " %s [%s]" % (title, url,))
# Then the downvotes and number of comments
vim.current. buffer .append( "↓ %s | comments: %s [%s]" % (down, comments, permalink,))
# And last we append some "-" for visual appeal.
vim.current. buffer .append( 80 * "-" )
except Exception, e:
print e
EOF
" Here the python code is closed. We can continue writing VimL or python again.
endfunction
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使用如下命令保存文件
然后调用该插件:
这个命令用起来不那么方便,因此我们再定义一个命令:
我们定义了命令:Reddit来调用这个函数。-nargs 参数声明命令行中有多少个参数。
关于函数参数的问题:
问:如何访问函数中的参数?
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function! SomeName(arg1, arg2, arg3)
" Get the first argument by name in VimL
let firstarg = a:arg1
" Get the second argument by position in Viml
let secondarg = a: 1
" Get the arguments in python
python << EOF
import vim
first_argument = vim. eval ( "a:arg1" ) #or vim.eval("a:0")
second_argument = vim. eval ( "a:arg2" ) #or vim.eval("a:1")
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你可以使用 ... 来处理可变个数参数来替换特定的参数名,可通过位置或者命名参数来访问,如:(arg1, arg2, ...)
问:如何在 Python 中调用 Vim 命令?
问:如何定义全局变量,并在 VimL 和 Python 中访问?
全局变量使用形如 g:. 的前缀,定义全局变量前应该检查该变量是否已定义:
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if !exists( "g:reddit_apicall_timeout" )
let g:reddit_apicall_timeout = 40
endif
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然后你通过下面代码在 Python 中访问这个变量:
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TIMEOUT = vim. eval ( "g:reddit_apicall_timeout" )
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可通过下面的方法来对全局变量进行重新赋值:
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let g:reddit_apicall_timeout = 60
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更多关于使用 Python 编写 Vim 插件的说明请看官方文档。
备注:
一旦你用过VimL,就会发现它挺简单的,你用python写的代码也可以用它来实现。详细请参考vim python模块文档,这是一份重要的参考资料。
除了上述文档,你也可以在IBM developerWorks网站找到一些有用的资料。