Python编程中常用的12种基础知识总结

>>>
line

=

'<IMG ALIGN="middle" SRC=\'#\'

"

/

span>

>>>
mo

=

re.

compile

(r

'(?<=SRC=)"([\w+\.]+)"'

,re.I)

>>>
mo.sub(r

'"\1****"'

,line)

'<IMG
ALIGN="middle" SRC=\'#\'

"

/

span>

>>>
mo.sub(r

'replace_str_\1'

,line)

'<IMG
ALIGN="middle" replace_str_overview.gif BORDER="0" ALT="">'

<

/

span>

>>>
mo.sub(r

'"testetstset"'

,line)

'<IMG
ALIGN="middle" SRC=\'#\'

"

/

span>

import

os

fileList

=

[]

rootdir

=

"/data"

for

root,
subFolders, files

in

os.walk(rootdir):

if

'.svn'

in

subFolders: subFolders.remove(

'.svn'

)

#
排除特定目录

for

file

in

files:

if

file

.find(

".t2t"

)!

=

-

1

:

#查找特定扩展名的文件

file_dir_path

=

os.path.join(root,

file

)

fileList.append(file_dir_path)

print

fileList

>>>a

=

[(

'2011-03-17'

,

'2.26'

,

6429600

,

'0.0'

),(

'2011-03-16'

,

'2.26'

,

12036900

,

'-3.0'

),

(

'2011-03-15'

,

'2.33'

,

15615500

,

'-19.1'

)]

>>>

print

a[

0

][

0

]

2011

-

03

-

17

>>>b

=

sorted

(a,key

=

lambda

result:result[

1

],reverse

=

True

)

>>>

print

b

[(

'2011-03-15'

,

'2.33'

,

15615500

,

'-19.1'

),(

'2011-03-17'

,

'2.26'

,

6429600

,

'0.0'

),

(

'2011-03-16'

,

'2.26'

,

12036900

,

'-3.0'

)]

>>>c

=

sorted

(a,key

=

lambda

result:result[

2

],reverse

=

True

)

>>>

print

c

[(

'2011-03-15'

,

'2.33'

,

15615500

,

'-19.1'

),(

'2011-03-16'

,

'2.26'

,

12036900

,

'-3.0'

),

(

'2011-03-17'

,

'2.26'

,

6429600

,

'0.0'

)]

>>>lst

=

[(

1

,

'sss'

),(

2

,

'fsdf'

),(

1

,

'sss'

),(

3

,

'fd'

)]

>>>

set

(lst)

set

([(

2

,

'fsdf'

),(

3

,

'fd'

),(

1

,

'sss'

)])

>>>

>>>lst

=

[

1

,

1

,

3

,

4

,

4

,

5

,

6

,

7

,

6

]

>>>

set

(lst)

set

([

1

,

3

,

4

,

5

,

6

,

7

])

>>>

from

operator

import

itemgetter

>>>aa

=

{

"a"

:

"1"

,

"sss"

:

"2"

,

"ffdf"

:

'5'

,

"ffff2"

:

'3'

}

>>>sort_aa

=

sorted

(aa.items(),key

=

itemgetter(

1

))

>>>sort_aa

[(

'a'

,

'1'

),(

'sss'

,

'2'

),(

'ffff2'

,

'3'

),(

'ffdf'

,

'5'

)]

>>>params

=

{

"server"

:

"mpilgrim"

,

"database"

:

"master"

,

"uid"

:

"sa"

,

"pwd"

:

"secret"

}

>>>[

"%s=%s"

%

(k, v)

for

k, v

in

params.items()]

[

'server=mpilgrim'

,

'uid=sa'

,

'database=master'

,

'pwd=secret'

]

>>>

";"

.join([

"%s=%s"

%

(k, v)

for

k, v

in

params.items()])

'server=mpilgrim;uid=sa;database=master;pwd=secret'

>>>a

=

'server=mpilgrim;uid=sa;database=master;pwd=secret'

>>>aa

=

{}

>>>

for

i

in

a.split(

';'

):aa[i.split(

'='

,

1

)[

0

]]

=

i.split(

'='

,

1

)[

1

]

...

>>>aa

{

'pwd'

:

'secret'

,

'database'

:

'master'

,

'uid'

:

'sa'

,

'server'

:

'mpilgrim'

}

将时间对象转换成字符串

>>>

import

datetime

>>>datetime.datetime.now().strftime(

"%Y-%m-%d%H:%M"

)

'2011-01-2014:05'

时间大小比较

>>>

import

time

>>>t1

=

time.strptime(

'2011-01-2014:05'

,

"%Y-%m-%d%H:%M"

)

>>>t2

=

time.strptime(

'2011-01-2016:05'

,

"%Y-%m-%d%H:%M"

)

>>>t1 > t2

False

>>>t1 < t2

True

时间差值计算,计算

8

小时前的时间

>>>datetime.datetime.now().strftime(

"%Y-%m-%d%H:%M"

)

'2011-01-2015:02'

>>>(datetime.datetime.now()

-

datetime.timedelta(hours

=

8

)).strftime(

"%Y-%m-%d%H:%M"

)

'2011-01-2007:03'

将字符串转换成时间对象

>>>endtime

=

datetime.datetime.strptime(

'20100701'

,

"%Y%m%d"

)

>>>

type

(endtime)

<

type

'datetime.datetime'

>

>>>

print

endtime

2010

-

07

-

01

00

:

00

:

00

将从

1970

-

01

-

01

00

:

00

:

00

UTC到现在的秒数，格式化输出  

>>>

import

time

>>>a

=

1302153828

>>>time.strftime(

"%Y-%m-%d%H:%M:%S"

,time.localtime(a))

'2011-04-0713:23:48'

#!/usr/bin/envpython

#-*- coding: utf-8 -*-

import

sys,os,getopt

def

usage():

print

'''''

Usage:analyse_stock.py [options...]

Options:

-e: Exchange Name

-c: User-Defined Category Name

-f: Read stock info from file and save to db

-d: delete from db by stock code

-n: stock name

-s: stock code

-h: this help info

test.py-s haha -n "HA Ha"

'''

try

:

opts,args

=

getopt.getopt(sys.argv[

1

:],

'he:c:f:d:n:s:'

)

except

getopt.GetoptError:

usage()

sys.exit()

if

len

(opts)

=

=

0

:

usage()

sys.exit()

for

opt,arg

in

opts:

if

opt

in

(

'-h'

,

'--help'

):

usage()

sys.exit()

elif

opt

=

=

'-d'

:

print

"delstock %s"

%

arg

elif

opt

=

=

'-f'

:

print

"readfile %s"

%

arg

elif

opt

=

=

'-c'

:

print

"user-defined%s "

%

arg

elif

opt

=

=

'-e'

:

print

"ExchangeName %s"

%

arg

elif

opt

=

=

'-s'

:

print

"Stockcode %s"

%

arg

elif

opt

=

=

'-n'

:

print

"Stockname %s"

%

arg 

sys.exit()

截取字符串输出,下面例子将只输出字符串的前

3

个字母

>>>

str

=

"abcdefg"

>>>

print

"%.3s"

%

str

abc

按固定宽度输出，不足使用空格补全,下面例子输出宽度为

10

>>>

str

=

"abcdefg"

>>>

print

"%10s"

%

str

abcdefg

截取字符串，按照固定宽度输出

>>>

str

=

"abcdefg"

>>>

print

"%10.3s"

%

str

abc

浮点类型数据位数保留

>>>

import

fpformat

>>>a

=

0.0030000000005

>>>b

=

fpformat.fix(a,

6

)

>>>

print

b

0.003000

对浮点数四舍五入,主要使用到

round

函数

>>>

from

decimal

import

*

>>>a

=

"2.26"

>>>b

=

"2.29"

>>>c

=

Decimal(a)

-

Decimal(b)

>>>

print

c

-

0.03

>>>c

/

Decimal(a)

*

100

Decimal(

'-1.327433628318584070796460177'

)

>>>Decimal(

str

(

round

(c

/

Decimal(a)

*

100

,

2

)))

Decimal(

'-1.33'

)

>>>num

=

10

>>>

print

"Hex = %x,Dec = %d,Oct = %o"

%

(num,num,num)

Hex

=

a,Dec

=

10

,

Oct

=

12

使用os.system() 调用系统命令 , 程序中无法获得到输出和返回值

>>>

import

os

>>>os.system(

'ls-l /proc/cpuinfo'

)

>>>os.system(

"ls-l /proc/cpuinfo"

)

-

r

-

-

r

-

-

r

-

-

1

root root

0

3

月

29

16

:

53

/

proc

/

cpuinfo

0

使用os.popen() 调用系统命令, 程序中可以获得命令输出，但是不能得到执行的返回值

>>>out

=

os.popen(

"ls-l /proc/cpuinfo"

)

>>>

print

out.read()

-

r

-

-

r

-

-

r

-

-

1

root root

0

3

月

29

16

:

59

/

proc

/

cpuinfo

使用commands.getstatusoutput() 调用系统命令, 程序中可以获得命令输出和执行的返回值

>>>

import

commands

>>>commands.getstatusoutput(

'ls/bin/ls'

)

(

0

,

'/bin/ls'

)

try

:

do_some_func()

except

KeyboardInterrupt:

print

"UserPress Ctrl+C,Exit"

except

EOFError:

print

"UserPress Ctrl+D,Exit"

一次性读入文件到列表，速度较快，适用文件比较小的情况下

track_file

=

"track_stock.conf"

fd

=

open

(track_file)

content_list

=

fd.readlines()

fd.close()

for

line

in

content_list:

print

line

逐行读入，速度较慢,适用没有足够内存读取整个文件(文件太大)

fd

=

open

(file_path)

fd.seek(

0

)

title

=

fd.readline()

keyword

=

fd.readline()

uuid

=

fd.readline()

fd.close()

写文件write 与 writelines 的区别  

Fd.write(

str

): 把

str

写到文件中，write()并不会在

str

后加上一个换行符

Fd.writelines(content): 把content的内容全部写到文件中,原样写入，不会在每行后面加上任何东西