1、文件操作流程：
-
打开文件，得到文件句柄并赋值给一个变量
-
通过句柄对文件进行操作
-
关闭文件
如下文件：
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2017
-
03
-
24
11
:
25
:
06
:
349
-
info: [debug] [AndroidBootstrap] Sending command to android: {
"cmd"
:
"shutdown"
}
2017
-
03
-
24
11
:
25
:
06
:
355
-
info: [debug] [AndroidBootstrap] Received command result
from
bootstrap
2017
-
03
-
24
11
:
25
:
06
:
356
-
info: [debug] [UiAutomator] Shutting down UiAutomator
2017
-
03
-
24
11
:
25
:
06
:
357
-
info: [debug] [UiAutomator] Moving to state
'stopping'
2017
-
03
-
24
11
:
25
:
06
:
360
-
info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data
from
client: {
"cmd"
:
"shutdown"
}
2017
-
03
-
24
11
:
25
:
06
:
361
-
info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of
type
SHUTDOWN
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操作流程：
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f
=
open
(
'log.txt'
,
'r'
)
print
(f.read())
f.close()
|
注意： 在win系统中log文件是utf8保存的，打开文件时open函数是通过操作系统打开的文件，而win操作系统默认的是gbk编码，所以直接打开会乱码，需要f=open('hello',encoding='utf8')，hello文件如果是gbk保存的，则直接打开即可。
2、文件打开模式
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# ========= ===============================================================
#
# Character Meaning
#
# --------- ---------------------------------------------------------------
#
# 'r' open for reading (default)
#
# 'w' open for writing, truncating the file first
#
# 'x' create a new file and open it for writing
#
# 'a' open for writing, appending to the end of the file if it exists
#
# 'b' binary mode
#
# 't' text mode (default)
#
# '+' open a disk file for updating (reading and writing)
#
# 'U' universal newline mode (deprecated)
#
# ========= ===============================================================
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3、文件操作方法
获取文件内容
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f
=
open
(
'log.txt'
,
'r'
)
data
=
f.read()
print
(data)
f.close()
|
输出：
2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"}
2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap
2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator
2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state 'stopping'
2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"}
2017-03-24 11:25:06:361 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of type SHUTDOWN
===========================================================================================
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2
3
4
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f =
open
(
'log.txt'
,
'r'
)
data1 = f.
read
(10)
#读取10个字符。（在这里汉字也只占一个单位）
print(data1)
f.close()
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输出：
2017-03-24
readline和readlines
===========================================================================================
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3
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f
=
open
(
'log.txt'
,
'r'
)
print
(f.readlines())
#返回的是一个列表，注意换行符
f.close()
|
输出：
['2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"}\n', '2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap\n', '2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator\n', "2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state 'stopping'\n", '2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"}\n', '2017-03-24 11:25:06:361 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of type SHUTDOWN']
===========================================================================================
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f
=
open
(
'log.txt'
,
'r'
)
print
(f.readline())
#逐行读取
print
(f.readline())
print
(f.readline()，f.readline()，f.readline())
#逐行读取，每行末尾换行符
f.close()
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输出：（注意每行末尾的换行符）
2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"}
2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap
2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator
2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state 'stopping'
2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"}
===========================================================================================
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f
=
open
(
'log.txt'
,
'r'
)
for
line
in
f.readlines():
print
(line.strip())
f.close()
|
输出：
2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"}
2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap
2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator
2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state 'stopping'
2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"}
2017-03-24 11:25:06:361 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of type SHUTDOWN
===========================================================================================
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2
3
4
5
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f
=
open
(
'log.txt'
,
'r'
)
print
(f)
for
i
in
f:
print
(i.strip())
f.close()
|
输出：
<_io.TextIOWrapper name='log.txt' mode='r' encoding='cp936'>
2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"}
2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap
2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator
2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state 'stopping'
2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"}
2017-03-24 11:25:06:361 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of type SHUTDOWN
===========================================================================================
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8
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n
=
0
f
=
open
(
'log.txt'
,
'r'
)
for
i
in
f:
if
n
=
=
3
:
i
=
'
'.join([i.strip(),'
this
is
line
4
'])
print
(i.strip())
n
+
=
1
f.close()
|
输出：
2017-03-24 11:25:06:349 - info: [debug] [AndroidBootstrap] Sending command to android: {"cmd":"shutdown"}
2017-03-24 11:25:06:355 - info: [debug] [AndroidBootstrap] Received command result from bootstrap
2017-03-24 11:25:06:356 - info: [debug] [UiAutomator] Shutting down UiAutomator
2017-03-24 11:25:06:357 - info: [debug] [UiAutomator] Moving to state 'stopping' this is line 4
2017-03-24 11:25:06:360 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got data from client: {"cmd":"shutdown"}
2017-03-24 11:25:06:361 - info: [AndroidBootstrap] [BOOTSTRAP LOG] [debug] Got command of type SHUTDOWN
===========================================================================================
tell和seek
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f
=
open
(
'log.txt'
,
'r'
)
print
(f.read(
25
))
print
(f.tell())
#取出光标所在位置
print
(f.seek(
0
))
#移动光标到指定的位置
print
(f.read(
50
))
f.close()
|
输出：
2017-03-24 11:25:06:349 -
25
0
2017-03-24 11:25:06:349 - info: [debug] [AndroidBo
注意：read后不管是中文字符还是英文字符,都统一算一个单位,read(6),此刻就读了6个中文字符；而seek和tell对于英文字符就是占一个,中文字符占三个,区分与read()的不同.
===========================================================================================
flush：同步把数据从缓存移动到磁盘上去
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#进度条实例
import
sys,time
for
i
in
range
(
30
):
sys.stdout.write(
"*"
)
sys.stdout.flush()
time.sleep(
0.1
)
#print的flush
import
sys,time
for
i
in
range
(
30
):
print
(
'*'
,end
=
'',flush
=
True
)
time.sleep(
0.1
)
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===========================================================================================
其他扩展：
#truncate（）：截断数据(不能在r模式下)
#在w模式下：先清空，再写，再截断
#在a模式下：直接将指定位置后的内容截断
# r+:光标默认在0位置开始写，从0开始覆盖数据
# w+:先清空，再写读
# a+:光标默认在最后位置
===========================================================================================
with：
为了避免打开文件后忘记关闭，可以通过管理上下文，即：
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with
open
(
'log.txt'
,
'r'
) as f:
print
(f.readline())
|
在Python 2.7 后，with又支持同时对多个文件的上下文进行管理，即：如此方式，当with代码块执行完毕时，内部会自动关闭并释放文件资源。
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#with 同时管理多个文件对象
with
open
(
'log1'
,
'r'
) as f_read,
open
(
'log2'
,
'w'
) as f_write:
for
line
in
f_read:
f_write.write(line)
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