import os

操作文件

# I use jupyter notebook to create some file
!touch foo.txt
!echo Hello > foo.txt
!cat foo.txt

Hello

# rename file
os.rename(\'foo.txt\',\'bar.txt\')
!cat bar.txt

Hello

# remove file
os.remove(\'bar.txt\')

改变目录

# current dir
print os.getcwd() # current working directory

/Users/yongle/OMOOC2py/cheat

# go down
os.chdir(\'img\')
print os.getcwd()

# go back up
os.chdir(os.pardir) #or simply os.chdir(\'..\')
print os.getcwd()

/Users/yongle/OMOOC2py/cheat/img
/Users/yongle/OMOOC2py/cheat

遍历目录listdir

# listdir
!touch a.txt b.txt
for file in os.listdir(\'.\'):
    # os.listdir() return a list
    if file.endswith(\'.txt\'):
        print file

a.txt
b.txt

遍历os.walk

os.chdir(\'doc\')

# Directory tree generator.
# For each dir in the dir tree rooted at top (including top
# itself, but excluding \'.\' and \'..\'), yields a 3-tuple
# dirpath, dirnames, filenames
for dirpath, dirnames, filenames in os.walk(\'.\'):
    print dirnames
    print filenames
    break # only one level needed, or just use listdir

[\'folder1\', \'folder2\']
[\'.DS_Store\', \'a.txt\', \'b.txt\']

增删目录

单层目录

# make a dir, one level, no duplication allowed
os.mkdir(\'test\')

# remove a dir, one level, not empty will raise OSError
os.rmdir(\'test\')

多层目录

# make dirs, multipul level
os.makedirs(\'test/mulitiple/levels\')

# remove all empty directories above it, ensure empty
os.removedirs(\'test/mulitiple/levels\')

非空目录

# remove non empty dir, ust a new module shutil.rmtree
# copy function is also useful
import shutil

# copy a.txt to backup folder
# or just shutil.copy(\'a.txt\',\'backup/\')
# use shutil.copytree to copy a folder like cp -r
os.mkdir(\'backup\')
shutil.copy(\'a.txt\',os.path.join(\'backup\',\'a_backup.txt\'))

# remove non empty folder
shutil.rmtree(\'backup/\')

os.path模块

# is a dir or not
print(os.path.isdir(\'img\'))
print(os.path.isdir(\'a.txt\'))

True
False

# is a file or not
print(os.path.isfile(\'img\'))
print(os.path.isfile(\'a.txt\'))

False
True

# determine the presence of path(a file or dir); os.path.lexists?
print(os.path.exists(\'img\'))
print(os.path.exists(\'a.txt\'))
print(os.path.exists(\'none_exist.txt\'))

True
True
False

# Join two or more pathname components, inserting \'/\' as needed.
# If any component is an absolute path, 
# all previous path components will be discarded.
print(os.path.join(\'/Users\',\'john\'))
print(os.path.join(\'/Users\',\'/john\'))
print(os.path.join(\'/Users\',\'john\',\'a.txt\'))

/Users/john
/john
/Users/john/a.txt

# split a pathname. Returns \"(head, tail)\" 
# where \"tail\" is everything after the final slash.
os.path.split(\'/Users/john/a.txt\')

(\'/Users/john\', \'a.txt\')

# split the extension from a pathname
os.path.splitext(\'/Users/john/a.txt\')

(\'/Users/john/a\', \'.txt\')

# determine the size of a path(file or dir)
os.path.getsize(\'a.txt\')

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