Python several important module memos

One: module invocation

Two: Time module

Three: System interface module OS and SYS

Four: Several modules of data preservation Json,pickle,xml,configparse

V: Data replication Mobile Module Shutil

Six: Random number randomly

Seven: Log module logging

Eight: Regular expression re

The module is used to split a program, just like a function or class to split a program. Splitting different functions of a program into multiple files can improve code readability. A py file may only complete an algorithm, or complete a socket, which can be called repeatedly. Python uses import to invoke the module, which can be either built-in or customizable, or open-source modules can be used

how to invoke the module:

Module1

defShowstar (num):#the way to count the stars    Print("Sky has%s star"%num)classStarsky:#number of stars of the class    def __init__(self,num): Self.num=num self.show ()defShow (self):Print("Sky has%s star"%self.num)

Called by

 Import Module1    # Importing module fromimport Starsky      #  Classes in the Import module  from import Showstar as show     # Import function in module #  When executed, the imported things will be parsed A=starsky (12)

If the relationship between Module1 and Module2 is:

| Caller. py
| __init__.py
|
\---Module_dir
module1.py
__init__.py

To invoke the Module1 method:

Import Module_dir.module1 as Mod1  from Import Starskya=starsky (12)Mod1.showstar

The key factor that can be imported is the environment variable, which executes the parent directory of the Python script as an environment variable:

Import sys>>> sys.path[' d:\\visual doc\\pyproject\\ Module Research topic ', ' e:\\ software \\python\\python35.zip ', ' e:\\ software \\python\\DLLs ', ' e:\\ software \\python\\lib ', ' e:\\ software \\python ', ' e:\\ software \\python\\lib\\site-packages ']
Module_dir under the D:\\visual doc\\pyproject\\ module study, so I found

If this is the case:

| module1.py
| __init__.py
|
\---Module_dir
__init__.py
Caller. py

The caller's parent directory Module_dir without Module1 will be an error.

Import syssys.path.append (".. "         #sys. Path is a list of environment variables, as long as you add the following: You can represent the parent directory of the Module1 import  Module1 as Mod1fromimport  Starskya= Starsky (Mod1.showstar) (12)

| __init__.py
| Caller. py
|
+---Module_dir
class1.py
module1.py
__init__.py

Caller calls Module1:import Module_dir.module1

Module1 Call Class1:import Class1

Execution of the caller, Class1 will not be found, because the environment variable is the caller's parent directory, Class1 in this directory can not be found, so in the import should be the Module_dir path to the environment variable

The absolute path to the parent directory of the Module1 __file__.

Import SYS Import ossys.path.append (Os.path.dirname (Os.path.abspath(__file__)))

So: one of the habits is that when you want to invoke another file in the current directory, save the absolute path of the current directory to the environment variable

A little bit more, each time you create a file, write the above code in.

Several important built-in modules:

1, Time module

Familiar with the C language of the time.h, analogy Python This module, are very similar, as a built-in module function, as long as you can use it.

Members	Parameters/Return	Description	Example/return results
Time.clock ()		Return Processor Time
Time.time ()	Return value: Time stamp of the current time	Returns the timestamp of the current time	Results: 1471246422.8152277
Time.ctime ()	Parameter one: Time stamp Return value: Time string	Default returns the current time, you can specify a timestamp, return time	Print (time.ctime (0)) Results: Thu Jan 1 08:00:00 1970
Time.gmtime () Time.localtime ()	Parameter one: Time stamp	LocalTime returns the struct_time of the current time Gmtime returns the time of the current green time zone	Time.struct_time ( tm_year=1970, Tm_mon=1, Tm_mday=1, Tm_hour=0, Tm_min=0, Tm_sec=0, Tm_wday=3, Tm_yday=1, tm_isdst=0)
Time.mktime ()	Parameter one: struct_time	Struct_time Convert to Timestamp
Time.strftime ()	Parameter one: Specify the format Parameter two: Incoming Struct_time Return: Format time string	Struct_time converted to format time, parameter one and the date of Linux	2016-08-15 08:02:28
Time.strptime ()	Parameter one: string Parameter two: Format return: Struct_time
Time.sleep ()	Parameter one: number of seconds	Specify time to Pause	Time.sleep (3) Pause for 3 seconds

Explanation of the time.h of->c language python time

2, operating system-related, OS and SYS modules

The OS module has functions that can execute the operating system commands, there are directory series (directory additions, deletions, moves, duplicates, attributes, soft and hard links), there are path series (current path, superior path, absolute path), many ...

To determine the current operating system:

Os.name windows--> ' nt ' linux/unix--> ' POSIX '

Sys.platform windows--> ' Win32 ' Linux--> ' Linux '

Direct command line operation:

Os.system (command) direct operation

The result of the Os.popen (cmd,mode,bufsize) command operation is returned to the variable, which returns the <os._wrap_close object at 0x000002308955dda0>

Catalogue/File Series:

Os.chdir (path) changes the current directory

Os.listdir (path) lists the files in the current directory

OS.GETCWD () absolute path to the current directory

Os.makedirs (path)/os.removedirs (path) to add/remove directories recursively

Os.remove (file) Delete

Os.rename (old,new) Rename

Path series

Os.environ/sys.path:

Os.environ is the environment variable of the system

Sys.path is the python default path

Os.path.abspath (path) parameter absolute path to path

Os.path.split (path) divides the parameter path into directories and files

Os.path.dirname (path)/os.path.basename (path)

Os.path.isdir (path)/os.path.isfile (file) to determine the path and files

Os.path.join (path,name) path and name merge

Os.path.splitext (file) file is split into file name and extension

SYS.ARGV Receive Run parameters

3, data documents and configuration documents:

Light weight data exchange Xml,json,ini

4,shutil files, folders, compressed package copies, copy file objects

5,logging Log Module

6,re Regular Expressions

Python several important module memos