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-- 218.25.66.198 [<<DateTime(2004-09-29T04:24:34Z)>>]
<<TableOfContents>>
= 描述 =

Finding a File Given an Arbitrary Search Path

在任意的搜索路径(集合)下，查找文件 
Credit: Chui Tey



== 问题 Problem ==
Given a search path (a string of directories with a separator in between), you need to find the first file along the path whose name is as requested. 

给定搜索路径(分隔符分开的欲搜索路径组成的字符串)，查找第一个名称符合的文件。 


== 解决 Solution ==
Basically, you need to loop over the directories in the given search path: 

一般来说，需要在给定的搜索路径集合上循环：
{{{
#!python
import os, string

def search_file(filename, search_path, pathsep=os.pathsep):
    """ Given a search path, find file with requested name """
    for path in string.split(search_path, pathsep):
        candidate = os.path.join(path, filename)
        if os.path.exists(candidate): return os.path.abspath(candidate)
    return None

if _ _name_ _ == '_ _ _main_ _':
    search_path = '/bin' + os.pathsep + '/usr/bin'  # ; on Windows, : on Unix
    find_file = search_file('ls',search_path)
    if find_file:
        print "File found at %s" % find_file
    else:
        print "File not found"
}}}
== 讨论 Discussion ==
This is a reasonably frequent task, and Python makes it extremely easy. The search loop can be coded in many ways, but returning the normalized path as soon as a hit is found is simplest as well as fast. The explicit return None after the loop is not strictly needed, since None is what Python returns when a function falls off the end, but having the return explicit in this case makes the functionality of search_file much clearer at first sight. 

这是一个很常见的任务，使用Python处理变得特简单。 循环语句可以采用很多风格实现，但是最简单又快速的方法是：发现一个符合条件文件立即返回它的规范化的路径。脚本中循环后面明确返回的None不是严格必需的，Python中函数没有返回值，默认返回一个None。不过，这里明确返回'''None''',使得代码(查找的)功能一眼就可以看得更清楚些。   

To find files specifically on Python's own search path, see Recipe 4.22. 

在Python的运行时搜索路径上查找文件，参见食谱 4.22 http://wiki.woodpecker.org.cn/moin.cgi/PyCkBk_2d4_2d22

== 参考 See Also ==

食谱4.22 http://wiki.woodpecker.org.cn/moin.cgi/PyCkBk_2d4_2d22;

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