Programing Python--sys Module

Recall that every Python module have a built_in __name__ variable that Python sets to the __main__ string Only if the file is run as a program,not when it ' s imported as library

So in the Python fiel if __name__ = = "__main__": .... Is the top-level code

1 " "2 Aplit and interactively page a string of file of text3 " "4 5 defMore (text,numlines= 15):6Lines =str.splitlines (text)7      whilelines:8Chunk =Lines[:numlines]9Lines =Lines[numlines:]Ten          forLineinchChunkPrint(line) One         ifLines andRaw_input ('More ?') not inch['y','Y']: Break A  -  - if __name__=="__main__": the     ImportSYS -More (open (sys.argv[0)). Read (), 10)

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When the more.py file is imported, we pass a explicit string to it more function,so this is the imported the More function

1  from Import  More 2 Import SYS 3 More (sys.  __doc__)

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Introducing the SYS Module

Platforms and Versions

1 if ' win ':print ('hello Windows')2elif'  Lin':print ('Hello linux')

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If You have code this must act differently on different machines, simply test the sys.platform string as done,

The Module Search Path

Sys.path is a list fo directory name strings representing the true search path in running Python interpreter when a modul E is imported Python scans this list from left to right,searching for the module's file on all directory named in the LIS T

The Sys.path list in simply initialized from your PYTHONPATH setting

Surprisingly,sys.path can actually is changed by program. Using Apend,extend,insert,pop,remove function

The Loaded Modules Table

Sys.modules is a dictionary containing one name:module entry for every module imported in your Python session

>>> Sys.modules

Excepstion detials

Other attribures in the SYS module allow us to fetch all the information related to the most recently Python exception,the Sys.exc_info function returns a tuple with the latest exception ' s Type,value and Traceback object

1 Try : 2     Raise Indexerror 3 except : 4     Print (Sys.exc_info ())

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Other SYS Module exports:

Command_line arguments show up as a list of string called SYS.ARGV

Standard streams is available as Sys.stdin sys.stdout and Sys.stderr

Program exit can is forced with sys.exit calls

Programing Python--sys Module