Python common modules

python-Common Modules

Python module

The module is the highest-level Python program organizational unit that encapsulates program code and data for reuse.

In practice, modules often correspond to Python program files. The essence is to use some code to implement certain functions of the collection

This collection can be a. py file, or it can be a package (in a folder that has a. PY entry file)

First, the Import module

Import Module

From module.xx import xx

From module.xx import xx as rename

From module.xx Import *

Import a py file, the interpreter interprets the file

Import a Package

Import module based on path Sys.path if you have this path, you can import it directly

If Sys.path has the desired path, pass sys.path.append (' path ')

Second, open source module

Download installation

1. Yum, Pip, Apt-get

2. Source code compilation Installation: Python setup.py build python setup Install

Three, common modules

1. OS module # used as a system-level work

Os.popen (' id '). read () # Execute system command Get return result

Os.system () # Get Return status returned cannot intercept

Os.name # Return to System platform Linux/unix user is ' POSIX '

Os.getenv () # Read environment variable

Os.putenv () # Setting environment variables

OS.GETCWD () # Current working path

Os.chdir () # Change the current working directory

Os.walk ('/root/') # recursive path

File processing

Mkfifo ()/mknod () # Create a named pipe/create a file system node

Remove ()/unlink () # Delete file

Rename ()/renames () # Rename File

*stat () # Return file information

Symlink () # Create Symbolic Links

Utime () # Update timestamp

Tmpfile () # Create and open (' W+b ') a new temporary file

Walk () # Traverse all filenames under the directory tree

Directory/Folder

ChDir ()/fchdir () # Change current working directory/change current working directory with a file descriptor

Chroot () # Changes the root directory of the current process

Listdir () # list files for the specified directory

GETCWD ()/getcwdu () # Returns the current working directory/function same, but returns a Unicode object

mkdir ()/makedirs () # Create a directory/create a multi-level directory

RmDir ()/removedirs () # Delete directory/delete multi- level directory

Access/Permissions

Saccess () # Verify permission mode

chmod () # Change permission mode

Chown ()/lchown () # Changes the owner and GroupID functions the same, but does not track links

Umask () # Set default permission mode

File descriptor Operations

Open () # Underlying operating system open (for robustness, use the standard built-in open () function)

Read ()/write () # Read/write data according to file descriptor read part of file by size

DUP ()/dup2 () # Copy file description symbol/function same, but copy to another file descriptor

Device number

Makedev () # Create an original device number from the major and minor device numbers

Major ()/minor () # Get the Major/minor device number from the original device number

Os.path Module

Os.path.expanduser (' ~/.ssh/key ') # full path to files in home directory

Separated

Os.path.basename () # Remove directory path, return file name

Os.path.dirname () # Remove file name, return directory path

Os.path.join () # Combine parts of a separate path name

Os.path.spllt () # Return (DirName (), basename ()) tuple

Os.path.splitdrive () # return (drivename,pathname) tuple

Os.path.splitext () # return (filename,extension) tuple

Information

Os.path.getatime () # Returns the last access time

Os.path.getctime () # Return file creation time

Os.path.getmtime () # Returns the last file modification time

Os.path.getsize () # Return file size (bytes)

Inquire

Os.path.exists () # Specifies whether the path (file or directory) exists

Os.path.isabs () # Specifies whether the path is an absolute path

Os.path.isdir () # Specifies whether the path exists and is a directory

Os.path.isfile () # Specifies whether the path exists and is a file

Os.path.islink () # Specifies whether the path exists and is a symbolic link

Os.path.ismount () # Specifies if the path exists and is a mount point

Os.path.samefile () # Two path names point to the same file

2. SYS module # provides interpreter-related operations

SYS.ARGV # command line argument list, the first element is the path of the program itself

Sys.exit (2) # Exit Script return status will be intercepted by try

Sys.exc_info () # Gets the exception class that is currently being processed

Sys.version # Get version information for Python interpreter

Sys.maxint # Maximum int value 9223372036854775807

Sys.maxunicode # maximum Unicode value

Sys.modules # Returns the system-imported module field, key is the module name, value is the module

Sys.path # Returns the search path of the module, using the value of the PYTHONPATH environment variable when initializing

Sys.platform # Returns the operating system platform name

Sys.stdout # Standard Output

Sys.stdin # Standard Input

Sys.stderr # Error Output

Sys.exec_prefix # Returns the location of the platform standalone Python file installation

Sys.stdin.readline () # reads a line from standard input

Sys.stdout.write ("a") # screen output a

3. Hashlib Module # for encryption-related operations

General Encryption

Import Hashlib

HASH_MD5 = HASHLIB.MD5 ()

Hash_md5.update (' admin ')

Print (Hash_md5.hexdigest ())

hash = hashlib.sha512 ()

Hash.update (' admin ')

Print Hash.hexdigest ()

#以上加密算法虽然依然非常厉害, but the time is flawed, namely: through the pool can be reversed. Therefore, it is necessary to add a custom key to the encryption algorithm to do encryption.

Add a custom key to do encryption

Import Hashlib

hash = hashlib.md5 (' 898oafs09f ')

Hash.update (' admin ')

Print hash.hexdigest ()

Super Cock Encryption-continue to encrypt the key and content we created

Import HMAC

h = hmac.new (' Wueiqi ')

H.update (' Hellowo ')

Print H.hexdigest ()

4. JSON and pickle modules #用于序列化数据

JSON, #json解决简单数据类型的序列换

Pickle, #能存储python的复杂数据类型

The JSON module provides four functions: dumps, dump, loads, load

The Pickle module provides four functions: dumps, dump, loads, load

Name_tra=json.dumps (' [1,2,3,4,5] ') #dunmps将序列化的数据放到内存

With open (' Json_tra ', ' WB ') as F_json:

F_json.write (Name_tra)

With open (' Json_tra1 ', ' WB ') as F_json: #dump直接将内存中序列化的数据写入文件

Json.dump (A,f_json)

Time_now=datetime.datetime.now ()

Pickle_mem=p.dumps (Time_now)

Pickle_load=p.loads (PICKLE_MEM)

5. Subprocess Module

Subprocess package to fork a child process and run an external program.

The subprocess package defines a number of functions that create child processes. Subprocess also provides some tools for managing standard streams and pipelines (pipe) to use text communication between processes.

Subprocess.call ()

Parent process waits for child process to complete

Return exit information (ReturnCode, equivalent to Linux exit code)

B=subprocess.call ([' ls ', '-l '])

B=subprocess.call ("Ls-l", Shell=true)

Shell=true, allows shell commands to be in string form.

Subprocess.check_call ()

Parent process waits for child process to complete

Returns 0

Check the exit information, and if ReturnCode is not 0, cite error subprocess. Calledprocesserror, this object contains the ReturnCode property, which can be try...except ... To check

Subprocess.check_call (["LS", "-l"])

Subprocess.check_call ("Exit 1", shell=true)

Subprocess.check_output ()

Parent process waits for child process to complete

Returns the output of the child process to the standard output

Check the exit information, and if ReturnCode is not 0, cite error subprocess. Calledprocesserror, which contains the ReturnCode property and the output property, outputs a result of the standard output, available try...except ... To check

6. Shuit Module #文件的复制移动

Shutil.copyfile (' data.db ', ' archive.db ') # Copy file

Shutil.move ('/build/executables ', ' installdir ') # move files or directories

7. Logging Module # Format logging

#通过logging. basicconfig function to configure the output format and mode of the log, the log will be written to the file

Logging.basicconfig (level=logging. DEBUG,

format= '% (asctime) s [line:% (Lineno) d]% (levelname) s% (message) s ',

datefmt= '%y/%m/%d%h:%m:%s ',

Filename= ' Myapp.log ',

Filemode= ' a ')

Logging.debug (' This is Debug message ')

Logging.info (' This is Info message ')

Logging.warning (' This is warning message ')

#logging. Basicconfig function Parameters:

#datefmt: Specify time format, same as Time.strftime ()

#filename: Specify the log file name

#filemode: The same as the file function, specify the open mode of the log file, ' W ' or ' a '

#level: Sets the logging level by default to logging. WARNING

#format: Specifies the format and content of the output, and format can output a lot of useful information, as shown in the previous example:

#% (asctime) s: Time to print logs

#% (levelname) S: Print log level name

#% (message) s: Print log information

#% (Levelno) S: Print the value of the log level

#% (Lineno) d: Print the current line number of the log

#% (pathname) s: Prints the path of the currently executing program, which is actually sys.argv[0]

#% (filename) S: Print the current execution program name

#% (funcName) s: Print the current function of the log

#% (thread) d: Print thread ID

#% (threadname) s: Print thread name

#% (process) d: Print process ID

#将日志同时写入文件, and print to the screen

Logging.basicconfig (level=logging. DEBUG,

format= '% (asctime) s% (filename) s[line:% (lineno) d]% (levelname) s% (message) s ',

datefmt= '%y/%m%d%h:%m:%s ',

Filename= ' Myapp.log ',

Filemode= ' W ')

#打印到屏幕

console = logging. Streamhandler ()

Console.setlevel (logging. WARNING)

Formatter = logging. Formatter ('% (name) -12s:% (levelname) -8s% (message) s ')

Console.setformatter (Formatter)

Logging.getlogger (). AddHandler (console)

8. The random module is used to take the stochastic number

Random.choice ([' Apple ', ' pear ', ' banana ') # random fetch list one parameter

Random.sample (xrange (100), 10) # 10 are not repeatedly extracted

Random.randrange (3,7) #随机抽取整数范围不包括7

Random.random () # Random floating point number

9. Time DateTime Module

Timestamp #1970年1月1日之后的秒, i.e.: Time.time ()

Formatted string # 2014-11-11 11:11, i.e.: Time.strftime ('%y-%m-%d ')

Structured time # Tuple contains: year, day, week, etc. time.struct_time is: time.localtime ()

Import time

Time.time () # timestamp [floating point]

Time.localtime () [1]-1 # last month

Int (Time.time ()) # timestamp [whole S]

Time.strftime ('%y-%m-%d%x ') #格式化输出时间

Import datetime

Datetime.datetime.datetime.now () #现在的时间

Datetime.datetime.now ()-Datetime.timedelta (days=5,hours=3,seconds=3,minutes=2) #减时间

10, re module regular matching

#Pattern对象是一个编译好的正则表达式, the text can be matched by a series of methods provided by the pattern.

Pattern=re.compile (strpattern[, flag]):

Flag is a matching pattern, re. I|re. M means that it takes effect simultaneously.

Re. I (re. IGNORECASE): Ignore case

M (MULTILINE): Multiline mode, changing the behavior of ' ^ ' and ' $ '

Match (string[, pos[, Endpos]) | Re.match (pattern, string[, flags]): #结果匹配一次

#match (string[, pos[, Endpos]) attempts to match pattern from the POS subscript of string and returns a match object if the pattern is still matched at the end;

The default values for POS and Endpos are 0 and Len (string), and Re.match () flags specify a matching pattern when compiling pattern.

#re. Match (pattern, string[, flags]) cannot specify POS and Endpos values. So the match is at the beginning of the match.

Search (string[, pos[, Endpos]) | Re.search (pattern, string[, flags]): #结果匹配一次

#search (string[, pos[, Endpos]) attempts to match pattern from the POS subscript of string, and returns a match object if the pattern is still matched at the end;

If the match is not matched, the POS is added 1 after the match is attempted again, and none is returned until Pos=endpos is still not matched.

#re. Search (pattern, string[, flags]), to match any start bit

A= ' 321.423.432.432 33.43.5.42 1.2.443.34 255.52.53.255 2.2.2.2 3.3.3.3 '

Pattern=re.compile (R ' ([12]?\d{1,2}\.) {3} ([12]?\d{1,2})

Print Pattern.search (a). Group ()

Split (string[, Maxsplit]) | Re.split (Pattern, string[, Maxsplit]):

Returns a list after splitting a string by a substring that can be matched. The maxsplit is used to specify the maximum number of splits and does not specify that all will be split.

#a = ' qwe123dsa43** ***2*342rew '

#print re.split (' [\d*]+ ', a)

FindAll (string[, pos[, Endpos]) | Re.findall (pattern, string[, flags]):

Searches for a string, returning all matching substrings as a list.

p = re.compile (R ' \d+ ')

Print P.findall (' One1two2three3four4 ')

Sub (repl, string[, Count]) | Re.sub (Pattern, REPL, string[, Count]):

Returns the replaced string after each matched substring in string is replaced with REPL.

Count is used to specify the maximum number of replacements, not all when specified.

A= ' 321.423.432.432 33.43.5.42 1.2.443.34 255.52.53.255 2.2.2.2 3.3.3.3 '

Pattern=re.compile (R ' ([12]?\d{1,2}\.) {3} ([12]?\d{1,2})

Print pattern.sub (' Bibi ', a)

Finditer (string[, pos[, Endpos]) | Re.finditer (pattern, string[, flags]):

Searches for a string that returns an iterator that accesses each matching result (match object) sequentially.

A= ' 321.423.432.432 33.43.5.42 1.2.443.34 255.52.53.255 2.2.2.2 3.3.3.3 '

Pattern=re.compile (R ' ([12]?\d{1,2}\.) {3} ([12]?\d{1,2})

For I in Pattern.finditer (a):

Print (I.group ())

Python common modules