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Python os.walk() 简介

Table of Contents

  • 1. os.walk目录遍历
    • 1.1. os.walk
    • 1.2. 例子
      • 1.2.1. 测试topdown
      • 1.2.2. 运行时修改遍历目录
  • 2. 参考资料

os.walk目录遍历

每个月都有那么几天想划水,又到划水的日子了,今天分享的是刚在处理遍历目录相关用到的相关方法。

os.walk

os.walk的参数如下:

os.walk(top, topdown=True, onerror=None, followlinks=False)

其中:

  • top是要遍历的目录。
  • topdown是代表要从上而下遍历还是从下往上遍历。
  • onerror可以用来设置当便利出现错误的处理函数(该函数接受一个OSError的实例作为参数),设置为空则不作处理。
  • followlinks表示是否要跟随目录下的链接去继续遍历,要注意的是,os.walk不会记录已经遍历的目录,所以跟随链接遍历的话有可能一直循环调用下去。

os.walk返回的是一个3个元素的元组 (root, dirs, files) ,分别表示遍历的路径名,该路径下的目录列表和该路径下文件列表。注意目录列表和文件列表不是具体路径,需要具体路径(从root开始的路径)的话可以用 os.path.join(root,dir)os.path.join(root,dir)

例子

假设现在存在如下的文件和目录结构:

test_os_walk git:(master)tree
.
├── a.py
├── b.py
├── c.py
├── dir1
│   ├── dir4
│   │   ├── g.py
│   │   └── h.py
│   ├── dirx
│   │   ├── diry
│   │   │   └── k.py
│   │   └── z.py
│   ├── e.py
│   ├── f.py
│   └── g.py
├── dir2
│   ├── dira
│   │   └── dirb
│   │       └── dirc
│   │           └── aha.py
│   ├── k.py
│   ├── l.py
│   └── m.py
└── dir3
    ├── dir5
    │   └── z.py
    ├── x.py
    └── y.py

10 directories, 17 files

测试topdown

当我用 os.walk 遍历这个目录时,程序和输出如下:

import os

path = '/Users/nisen/Projects/python_advanced_class/test/test_os_walk'

for root, dirs, files in os.walk(path, True):
    print 'root: %s' % root
    print 'dirs: %s' % dirs
    print 'files: %s' % files
    print ''

结果如下,从root的路径可以看出遍历是自上而下的:

➜  test git:(master) ✗ python test11.py
root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk
dirs: ['dir1', 'dir2', 'dir3']
files: ['a.py', 'b.py', 'c.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir1
dirs: ['dir4', 'dirx']
files: ['e.py', 'f.py', 'g.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir1/dir4
dirs: []
files: ['g.py', 'h.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir1/dirx
dirs: ['diry']
files: ['z.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir1/dirx/diry
dirs: []
files: ['k.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir2
dirs: ['dira']
files: ['k.py', 'l.py', 'm.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir2/dira
dirs: ['dirb']
files: []

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir2/dira/dirb
dirs: ['dirc']
files: []

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir2/dira/dirb/dirc
dirs: []
files: ['aha.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir3
dirs: ['dir5']
files: ['x.py', 'y.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir3/dir5
dirs: []
files: ['z.py']

而当设置os.walk的topdown为False时,结果如下, 可以看出他是自上而下遍历的:

➜  test git:(master) ✗ python test11.py
root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir1/dir4
dirs: []
files: ['g.py', 'h.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir1/dirx/diry
dirs: []
files: ['k.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir1/dirx
dirs: ['diry']
files: ['z.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir1
dirs: ['dir4', 'dirx']
files: ['e.py', 'f.py', 'g.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir2/dira/dirb/dirc
dirs: []
files: ['aha.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir2/dira/dirb
dirs: ['dirc']
files: []

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir2/dira
dirs: ['dirb']
files: []

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir2
dirs: ['dira']
files: ['k.py', 'l.py', 'm.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir3/dir5
dirs: []
files: ['z.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk/dir3
dirs: ['dir5']
files: ['x.py', 'y.py']

root: /Users/nisen/Projects/python_advanced_class/test/test_os_walk
dirs: ['dir1', 'dir2', 'dir3']
files: ['a.py', 'b.py', 'c.py']

运行时修改遍历目录

当topdown设置为True时,可以在处理时修改返回的 dirs 列表,这样可以遍历下面的目录时会根据修改后的 dirs 来遍历。比如下面的例子,在遍历的时候不把”CSV”目录包括在内:

import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
    print root, "consumes",
    print sum(getsize(join(root, name)) for name in files),
    print "bytes in", len(files), "non-directory files"
    if 'CVS' in dirs:
        dirs.remove('CVS')  # don't visit CVS directories

参考资料

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