Python用法速查@文件操作

文本文件

os.path.exists('path/file.txt')

>>>os.path.exists("C://ArcMentalTest//config.txt")
True

f=open(path, mode)

data=f.read()

r	读
w	写
a	追加
b	二进制
+	读/写

try:
    f = open('/path/to/file', 'r')    # 打开文件
    data = f.read()                   # 读取文件内容
finally:
    if f:
        f.close()                     # 确保文件被关闭

with open(path, mode)

with open('/path/to/file', 'r') as f: #会自动关闭文件
    data = f.read()

f.read(1024)

适用于文件较大的情况，如10G不想一次性读完

with open('path/to/file', 'r') as f:
    while True:
        piece = f.read(1024)        # 每次读取 1024 个字节（即 1 KB）的内容
        if not piece:
            break
        print piece

yield data

def read_in_chunks(file_object, chunk_size=1024):
    """
	Lazy function (generator) to read a file piece by piece.
    Default chunk size: 1k.
	"""
	
    while True:
        data = file_object.read(chunk_size)
        if not data:
            break
        yield data    #可多次返回数据

with open('path/to/file', 'r') as f:
    for piece in read_in_chunks(f):
        print piece

f.readline()

with open('data.txt', 'r') as f:
    while True:
        line = f.readline()     # 逐行读取
        if not line:
            break
        print line,             # 这里加了 ',' 是为了避免 print 自动换行

f.readlines()

file.txt
-------------------------
This a test .
a file named file.txt
txt is the expend name...
-------------------------
with open('./file.txt', 'r') as f:
    line = f.readline()
    print(line)
-------------------------
This a test .

file.txt
-------------------------
10  1   9   9
6   3   2   8
20  10  3   23
1   4   1   10
10  8   6   3
10  2   1   6
-------------------------
with open('data.txt', 'r') as f:
    lines = f.readlines() #按行读生成字符串列表
    line_num = len(lines)
    print lines
    print line_num
------------------------
['10	1	9	9
', '6	3	2	8
', '20	10	3	23
', '1	4	1	10
', '10	8	6	3
', '10	2	1	6']
6


file.txt
-------------------------
This a test .
a file named file.txt
txt is the expend name...
-------------------------
with open('./file.txt', 'r') as f:
    lines = f.readlines()
    print(lines)

['This a test .
', 'a file named file.txt
', 'txt is the expend name...']

for line in f:...迭代器

with open('data.txt', 'r') as f:
    for line in f:
        print line,
-------------------------------
10  1   9   9
6   3   2   8
20  10  3   23
1   4   1   10
10  8   6   3
10  2   1   6

with open(file_path, 'r') as f:
    lines = list(f)
    print lines
------------------------------

['10	1	9	9
', '6	3	2	8
', '20	10	3	23
', '1	4	1	10
', '10	8	6	3
', '10	2	1	6']

f.write('message ')

with open('/Users/ethan/data2.txt', 'w') as f:
    f.write('one
') #覆盖写，文件不存在则创建
    f.write('two')


with open('/Users/ethan/data2.txt', 'a') as f: #追加写
    f.write('three
')
    f.write('four')

二进制文件

with open(path, 'rb') as f:...

f.read()

with open('./image/plain.png', 'rb') as f:
    bs = f.read() #生成字节字符串
    print(bs)

#结果
b'x89PNG
x1a
x00x00x00
IHDRx00x00x00xcex00x00x00xc8x08x06x00x00x00xa0Fxdexd9x00x00	xb6IDATxx9cxedxddAkx1bxcdx1dxc7qxbdx04xbfx82xd5x84x1eJz(x82\J!`zxf1xd59...x00x00x00x00x00x00x00x00x00x00x00x000xbbxfex0fxebx04xd6xd6xd5]xb9xe3x00x00x00x00IENDxaeB`x82'

data=base64.b64encode(byte_data)

import base64
with open('./image/plain.png', 'rb') as f:
    bs = f.read()
    data_64 = base64.b64encode(bs) #对字节字符串进行base64编码
    print(data_64)
	
#结果
b'iVBORw0KGgoAAAANSUhEUgAAAM4AAADICAYAAACgRt7ZAAAJtklEQVR4nO3dQWsbzR3Hcb0Ev4LVhB5KeiiCXEohYHrx1Tn18FDwJZenF9OjT6I80u4DT+xC4MGEFptATSkpgfDg0l5Wz+E5+WD8XAKWRls/kXkcJa1MmtakwUwPkv04sXdm15rZ2bW+H5irLK33tzszO...AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAwu/4P6wTW1tVdueMAAAAASUVORK5CYII='

with open(path, 'wb') as f:...

f.write(byte_data)

with open('test.png', 'rb') as f:
    image_data = f.read()

with open('/Users/ethan/test2.png', 'wb') as f:
    f.write(image_data)

操作系统OS模块

os.mkdir	创建目录
os.rmdir	删除目录
os.rename	重命名
os.remove	删除文件
os.getcwd	获取当前工作路径
os.walk	遍历目录
os.path.join	连接目录与文件名
os.path.split	分割文件名与目录
os.path.abspath	获取绝对路径
os.path.dirname	获取路径
os.path.basename	获取文件名或文件夹名
os.path.splitext	分离文件名与扩展名
os.path.isfile	判断给出的路径是否是一个文件
os.path.isdir	判断给出的路径是否是一个目录

os.path.abspath(dir_name/file_name)

$ pwd
/Users/ethan/coding/python
$ python
>>> import os                          # 记得导入 os 模块
>>> os.path.abspath('hello.py')        # 获取文件绝对路径
'/Users/ethan/coding/python/hello.py'
>>> os.path.abspath('web')
'/Users/ethan/coding/python/web'
>>> os.path.abspath('.')                # 当前目录的绝对路径
'/Users/ethan/coding/python'

os.path.dirname(dirXpath/fileXpath)

>>> os.path.dirname('/Users/ethan/coding/python/hello.py')#获取文件路径
'/Users/ethan/coding/python'
>>> os.path.dirname('/Users/ethan/coding/python/')#获取文件夹路径
'/Users/ethan/coding/python'
>>> os.path.dirname('/Users/ethan/coding/python')
'/Users/ethan/coding'

os.path.basename(Xpath)

>>> os.path.basename('/Users/ethan/coding/python/hello.py')#获取文件名
'hello.py'
>>> os.path.basename('/Users/ethan/coding/python/')#获取文件夹名
''
>>> os.path.basename('/Users/ethan/coding/python')
'python'

os.path.splitext(Xpath)

>>> os.path.splitext('/Users/ethan/coding/python/hello.py')#分割文件名和扩展名
('/Users/ethan/coding/python/hello', '.py')
>>> os.path.splitext('/Users/ethan/coding/python')
('/Users/ethan/coding/python', '')
>>> os.path.splitext('/Users/ethan/coding/python/')
('/Users/ethan/coding/python/', '')

os.path.split(Xpath)

>>> os.path.split('/Users/ethan/coding/python/hello.py')#分离目录和文件名
('/Users/ethan/coding/python', 'hello.py')
>>> os.path.split('/Users/ethan/coding/python/')
('/Users/ethan/coding/python', '')
>>> os.path.split('/Users/ethan/coding/python')
('/Users/ethan/coding', 'python')

os.path.isfile(Xpath)

os.path.isdir(Xpath)

>>> os.path.isfile('/Users/ethan/coding/python/hello.py')#判断是否为文件
True
>>> os.path.isdir('/Users/ethan/coding/python/')#是否为目录
True
>>> os.path.isdir('/Users/ethan/coding/python')
True
>>> os.path.isdir('/Users/ethan/coding/python/hello.py')
False

for xpath, dirname, filename in os.walk(Xpath):...

>>> for root, dirs, files in os.walk('/Users/ethan/coding'):
...     print root
...     print dirs
...     print files
...
/Users/ethan/coding #绝对路径
['python']          #文件夹
[]                  #文件
/Users/ethan/coding/python
['web2']
['hello.py']
/Users/ethan/coding/python/web2
[]
[]
---------------------------------------------
import os
for root, dirs, files in os.walk("E://PYTHON//Basics//Fun", topdown=True):
    print(root)
    print(dirs)
    print(files)
#结果
D:pythonpython.exe E:/PYTHON/Basics/Fun/HelloYoutube.py
E://PYTHON//Basics//Fun
['.idea', 'image', '__pycache__']
['Ball.py', 'Calculator.py', 'Editor.py', 'file.txt', 'HelloYoutube.py', 'tttGame.py']
E://PYTHON//Basics//Fun.idea
['inspectionProfiles']
['Fun.iml', 'misc.xml', 'modules.xml', 'workspace.xml']
E://PYTHON//Basics//Fun.ideainspectionProfiles
[]
['profiles_settings.xml']
E://PYTHON//Basics//Funimage
[]
['airship.png', 'city.png', 'cold.png', 'exit.png', 'hot.png', 'icon_love.png', 'lo.gif', 'open.png', 'plain.png', 'save.png']
E://PYTHON//Basics//Fun\__pycache__
[]
['Ball.cpython-39.pyc']

Process finished with exit code 0
-----------------------------------------
import os
for root, dirs, files in os.walk("E://PYTHON//Basics//Fun", topdown=False):
    for name in files:
        print(os.path.join(root, name))
    for name in dirs:
        print(os.path.join(root, name))

#结果

D:pythonpython.exe E:/PYTHON/Basics/Fun/HelloYoutube.py
E://PYTHON//Basics//Fun.ideainspectionProfilesprofiles_settings.xml
E://PYTHON//Basics//Fun.ideaFun.iml
E://PYTHON//Basics//Fun.ideamisc.xml
E://PYTHON//Basics//Fun.ideamodules.xml
E://PYTHON//Basics//Fun.ideaworkspace.xml
E://PYTHON//Basics//Fun.ideainspectionProfiles
E://PYTHON//Basics//Funimageairship.png
E://PYTHON//Basics//Funimagecity.png
E://PYTHON//Basics//Funimagecold.png
E://PYTHON//Basics//Funimageexit.png
E://PYTHON//Basics//Funimagehot.png
E://PYTHON//Basics//Funimageicon_love.png
E://PYTHON//Basics//Funimagelo.gif
E://PYTHON//Basics//Funimageopen.png
E://PYTHON//Basics//Funimageplain.png
E://PYTHON//Basics//Funimagesave.png
E://PYTHON//Basics//Fun\__pycache__Ball.cpython-39.pyc
E://PYTHON//Basics//FunBall.py
E://PYTHON//Basics//FunCalculator.py
E://PYTHON//Basics//FunEditor.py
E://PYTHON//Basics//Funfile.txt
E://PYTHON//Basics//FunHelloYoutube.py
E://PYTHON//Basics//Fun	ttGame.py
E://PYTHON//Basics//Fun.idea
E://PYTHON//Basics//Funimage
E://PYTHON//Basics//Fun\__pycache__

Process finished with exit code 0

参考

explore-python/File-Dirctory