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, οnerrοr=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) 和 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