Python读取文件目录树——os.walk

Python读取文件目录树——os.walk

os.walk是Python的内置函数用来遍历文件目录树。
[python]
import os 
 
rootDir = 'd:\\assa' 
for dirName, subdirList, fileList in os.walk(rootDir): 
    print('Folder: %s' % dirName) 
    for fname in fileList: 
        print('\t%s' % fname) 

import os

rootDir = 'd:\\assa'
for dirName, subdirList, fileList in os.walk(rootDir):
 print('Folder: %s' % dirName)
 for fname in fileList:
  print('\t%s' % fname)目录结构为：

[python]
+test 
    +f1 
        2.txt 
    +f2 
        3.txt 
    1.txt 

+test
 +f1
  2.txt
 +f2
  3.txt
 1.txt输出结果为：
[python]
Folder: d:\Python Code\test 
    1.txt 
Folder: d:\Python Code\test\f1 
    2.txt 
Folder: d:\Python Code\test\f2 
    3.txt 

Folder: d:\Python Code\test
 1.txt
Folder: d:\Python Code\test\f1
 2.txt
Folder: d:\Python Code\test\f2
 3.txt可以看到这是自顶向下的遍历顺序，如果我们要自底向上，先从最深处的文件开始遍历，可以加上topdown参数：[python] view plaincopyprint?import os 
 
rootDir = 'd:\\Python Code\\test' 
for dirName, subdirList, fileList in os.walk(rootDir, topdown = False): 
    print('Folder: %s' % dirName) 
    for fname in fileList: 
        print('\t%s' % fname) 

import os

rootDir = 'd:\\Python Code\\test'
for dirName, subdirList, fileList in os.walk(rootDir, topdown = False):
 print('Folder: %s' % dirName)
 for fname in fileList:
  print('\t%s' % fname)结果：
[python]
Folder: d:\Python Code\test\f1 
    2.txt 
Folder: d:\Python Code\test\f2 
    3.txt 
Folder: d:\Python Code\test 
    1.txt 

Folder: d:\Python Code\test\f1
 2.txt
Folder: d:\Python Code\test\f2
 3.txt
Folder: d:\Python Code\test
 1.txt如果想要在搜索的时候加上条件？比如跳过第一个文件夹，os.walk也可以做到：[python] view plaincopyprint?import os 
 
rootDir = 'd:\\Python Code\\test' 
for dirName, subdirList, fileList in os.walk(rootDir): 
    print('Folder: %s' % dirName) 
    for fname in fileList: 
        print('\t%s' % fname) 
    if len(subdirList) > 0: 
        del subdirList[0] 

import os

rootDir = 'd:\\Python Code\\test'
for dirName, subdirList, fileList in os.walk(rootDir):
 print('Folder: %s' % dirName)
 for fname in fileList:
  print('\t%s' % fname)
 if len(subdirList) > 0:
  del subdirList[0]结果：
[python]
Folder: d:\Python Code\test 
    1.txt 
Folder: d:\Python Code\test\f2 
    3.txt 

Folder: d:\Python Code\test
 1.txt
Folder: d:\Python Code\test\f2
 3.txt有的同学却不能得到正确的结果，我们可以看看如下代码：
[python]
import os 
 
rootDir = 'd:\\Python Code\\test' 
for dirName, subdirList, fileList in os.walk(rootDir): 
    print('Folder: %s' % dirName) 
    for fname in fileList: 
        print('\t%s' % fname) 
    if len(subdirList) > 0: 
        subdirList = subdirList[1:] 

import os

rootDir = 'd:\\Python Code\\test'
for dirName, subdirList, fileList in os.walk(rootDir):
 print('Folder: %s' % dirName)
 for fname in fileList:
  print('\t%s' % fname)
 if len(subdirList) > 0:
  subdirList = subdirList[1:]
结果：

[python]
Folder: d:\Python Code\test 
    1.txt 
Folder: d:\Python Code\test\f1 
    2.txt 
Folder: d:\Python Code\test\f2 
    3.txt 

Folder: d:\Python Code\test
 1.txt
Folder: d:\Python Code\test\f1
 2.txt
Folder: d:\Python Code\test\f2
 3.txt

看起来和之前的版本相似，但是却不能得到期望的结果。这是因为我们没有就地改变subdirList的值：
[python]
>> a=[1,2,3] 
>>> id(a) 
34006600 
>>> del a[0] 
>>> id(a) 
34006600 
>>> a = a[1:] 
>>> id(a) 
34006024 

>>> a=[1,2,3]
>>> id(a)
34006600
>>> del a[0]
>>> id(a)
34006600
>>> a = a[1:]
>>> id(a)
34006024