使用 fileinput 模块循环一个文本文件
import
fileinput
import
sys
for
line
in
fileinput.
input
(
"samples/sample.txt"
):
sys.stdout.write(
"-> "
)
sys.stdout.write(line)
-
> We will perhaps eventually be writing only small
-
> modules which are identified by name as they are
-
> used to build larger ones, so that devices like
-
> indentation, rather than delimiters, might become
-
> feasible
for
expressing local structure
in
the
-
> source language.
-
>
-
-
Donald E. Knuth, December
1974
|
你也可以使用 fileinput 模块获得当前行的元信息 (meta information). 其中包括 isfirstline , filename , lineno
使用 fileinput 模块处理多个文本文件
import
fileinput
import
glob
import
string, sys
for
line
in
fileinput.
input
(glob.glob(
"samples/*.txt"
)):
if
fileinput.isfirstline():
# first in a file?
sys.stderr.write(
"-- reading %s --\n"
%
fileinput.filename())
sys.stdout.write(
str
(fileinput.lineno())
+
" "
+
string.upper(line))
-
-
reading samples\sample.txt
-
-
1
WE WILL PERHAPS EVENTUALLY BE WRITING ONLY SMALL
2
MODULES WHICH ARE IDENTIFIED BY NAME AS THEY ARE
3
USED TO BUILD LARGER ONES, SO THAT DEVICES LIKE
4
INDENTATION, RATHER THAN DELIMITERS, MIGHT BECOME
5
FEASIBLE FOR EXPRESSING LOCAL STRUCTURE IN THE
6
SOURCE LANGUAGE.
7
-
-
DONALD E. KNUTH, DECEMBER
1974
|
文本文件的替换操作很简单. 只需要把 inplace 关键字参数设置为 1 , 传递给 input 函数, 该模块会帮你做好一切.
使用 fileinput 模块将 CRLF 改为 LF
import
fileinput, sys
for
line
in
fileinput.
input
(inplace
=
1
):
# convert Windows/DOS text files to Unix files
if
line[
-
2
:]
=
=
"\r\n"
:
line
=
line[:
-
2
]
+
"\n"
sys.stdout.write(line)
|
shutil 实用模块包含了一些用于复制文件和文件夹的函数.
使用 shutil 复制文件
import
shutil
import
os
for
file
in
os.listdir(
"."
):
if
os.path.splitext(
file
)[
1
]
=
=
".py"
:
print
file
shutil.copy(
file
, os.path.join(
"backup"
,
file
))
aifc
-
example
-
1.py
anydbm
-
example
-
1.py
array
-
example
-
1.py
...
|
copytree 函数用于复制整个目录树 (与 cp -r 相同), 而 rmtree 函数用于删除整个目录树 (与 rm -r )
使用 shutil 模块复制/删除目录树
import
shutil
import
os
SOURCE
=
"samples"
BACKUP
=
"samples-bak"
# create a backup directory
shutil.copytree(SOURCE, BACKUP)
print
os.listdir(BACKUP)
# remove it
shutil.rmtree(BACKUP)
print
os.listdir(BACKUP)
[
'sample.wav'
,
'sample.jpg'
,
'sample.au'
,
'sample.msg'
,
'sample.tgz'
,
...
Traceback (most recent call last):
File
"shutil-example-2.py"
, line
17
,
in
?
print
os.listdir(BACKUP)
os.error: No such
file
or
directory
|
tempfile 模块允许你快速地创建名称唯一的临时文件供使用.
使用 tempfile 模块创建临时文件
import
tempfile
import
os
tempfile
=
tempfile.mktemp()
print
"tempfile"
,
"=>"
, tempfile
file
=
open
(tempfile,
"w+b"
)
file
.write(
"*"
*
1000
)
file
.seek(
0
)
print
len
(
file
.read()),
"bytes"
file
.close()
try
:
# must remove file when done
os.remove(tempfile)
except
OSError:
pass
tempfile
=
> C:\TEMP\~
160
-
1
1000
bytes
|
TemporaryFile 函数会自动挑选合适的文件名, 并打开文件而且它会确保该文件在关闭的时候会被删除. (在 Unix 下, 你可以删除一个已打开的文件, 这 时文件关闭时它会被自动删除. 在其他平台上, 这通过一个特殊的封装类实现.)
使用 tempfile 模块打开临时文件
import
tempfile
file
=
tempfile.TemporaryFile()
for
i
in
range
(
100
):
file
.write(
"*"
*
100
)
file
.close()
# removes the file!
|
StringIO 模块的使用. 它实现了一个工作在内存的文件对象 (内存文件). 在大多需要标准文件对象的地方都可以使用它来替换.
使用 StringIO 模块从内存文件读入内容
import
StringIO
MESSAGE
=
"That man is depriving a village somewhere of a computer scientist."
file
=
StringIO.StringIO(MESSAGE)
print
file
.read()
That man
is
depriving a village somewhere of a computer scientist.
|
StringIO 类实现了内建文件对象的所有方法, 此外还有 getvalue 方法用来返回它内部的字符串值
使用 StringIO 模块向内存文件写入内容
import
StringIO
file
=
StringIO.StringIO()
file
.write(
"This man is no ordinary man. "
)
file
.write(
"This is Mr. F. G. Superman."
)
print
file
.getvalue()
This man
is
no ordinary man. This
is
Mr. F. G. Superman.
|
使用 StringIO 模块捕获输出
import
StringIO
import
string, sys
stdout
=
sys.stdout
sys.stdout
=
file
=
StringIO.StringIO()
print
"""
According to Gbaya folktales, trickery and guile
are the best ways to defeat the python, king of
snakes, which was hatched from a dragon at the
world's start. -- National Geographic, May 1997
"""
sys.stdout
=
stdout
print
string.upper(
file
.getvalue())
ACCORDING TO GBAYA FOLKTALES, TRICKERY AND GUILE
ARE THE BEST WAYS TO DEFEAT THE PYTHON, KING OF
SNAKES, WHICH WAS HATCHED FROM A DRAGON AT THE
WORLD'S START.
-
-
NATIONAL GEOGRAPHIC, MAY
1997
|
cStringIO 是一个可选的模块, 是 StringIO 的更快速实现. 它的工作方式和 StringIO 基本相同, 但是它不可以被继承
使用 cStringIO 模块
import
cStringIO
MESSAGE
=
"That man is depriving a village somewhere of a computer scientist."
file
=
cStringIO.StringIO(MESSAGE)
print
file
.read()
That man
is
depriving a village somewhere of a computer scientist.
|
为了让你的代码尽可能快, 但同时保证兼容低版本的 Python ,你可以使用一个小技巧在 cStringIO 不可用时启用 StringIO 模块,
后退至 StringIO
try
:
import
cStringIO
StringIO
=
cStringIO
except
ImportError:
import
StringIO
print
StringIO
<module
'StringIO'
(built
-
in
)>
|
mmap 模块提供了操作系统内存映射函数的接口, 映射区域的行为和字符串对象类似, 但数据是直接从文件读取的.
使用 mmap 模块
import
mmap
import
os
filename
=
"samples/sample.txt"
file
=
open
(filename,
"r+"
)
size
=
os.path.getsize(filename)
data
=
mmap.mmap(
file
.fileno(), size)
# basics
print
data
print
len
(data), size
# use slicing to read from the file
# 使用切片操作读取文件
print
repr
(data[:
10
]),
repr
(data[:
10
])
# or use the standard file interface
# 或使用标准的文件接口
print
repr
(data.read(
10
)),
repr
(data.read(
10
))
<mmap
object
at
008A2A10
>
302
302
'We will pe'
'We will pe'
'We will pe'
'rhaps even'
|
在 Windows 下, 这个文件必须以既可读又可写的模式打开( `r+` , `w+` , 或 `a+` ), 否则 mmap 调用会失败.
对映射区域使用字符串方法和正则表达式
mport mmap
import
os, string, re
def
mapfile(filename):
file
=
open
(filename,
"r+"
)
size
=
os.path.getsize(filename)
return
mmap.mmap(
file
.fileno(), size)
data
=
mapfile(
"samples/sample.txt"
)
# search
index
=
data.find(
"small"
)
print
index,
repr
(data[index
-
5
:index
+
15
])
# regular expressions work too!
m
=
re.search(
"small"
, data)
print
m.start(), m.group()
43
'only small\015\012modules '
43
small
|
==============================================================================
本文转自被遗忘的博客园博客，原文链接：http://www.cnblogs.com/rollenholt/archive/2011/11/27/2264946.html，如需转载请自行联系原作者
