python sys is not defined

Question

I have a piece of code which is working in Linux  and I am now trying to run it in windows  I import sys but when I use sys exit    I get an error  sys is not defined  Here is the begining part of my code  try      import numpy as np     import pyfits as pf     import scipy ndimage as nd     import pylab as pl     import os     import heapq     import sys     from scipy optimize import leastsq  except ImportError      print  Error  missing one of the libraries  numpy  pyfits  scipy  matplotlib       sys exit     Why is sys not working

User · Accepted Answer

Move import sys outside of the try-except block   import sys try            except ImportError              If any of the imports before the import sys line fails  the rest of the block is not executed  and sys is never imported  Instead  execution jumps to the exception handling block  where you then try to access a non-existing name   sys is a built-in module anyway  it is always present as it holds the data structures to track imports  if importing sys fails  you have bigger problems on your hand  as that would indicate that all module importing is broken

User · Answer

In addition to the answers given above  check the last line of the error message in your console  In my case  the  site-packages  path in sys path append          was wrong

User · Answer

I m guessing your code failed BEFORE import sys  so it can t find it when you handle the exception   Also  you should indent the your code whithin the try block   try   import sys      other safe imports try      import numpy as np       other unsafe imports except ImportError      print  Error  missing one of the libraries  numpy  pyfits  scipy  matplotlib       sys exit

User · Answer

You re trying to import all of those modules at once  Even if one of them fails  the rest will not import  For example   try      import datetime     import foo     import sys except ImportError      pass   Let s say foo doesn t exist  Then only datetime will be imported   What you can do is import the sys module at the beginning of the file  before the try except statement   import sys try      import numpy as np     import pyfits as pf     import scipy ndimage as nd     import pylab as pl     import os     import heapq     from scipy optimize import leastsq  except ImportError      print  Error  missing one of the libraries  numpy  pyfits  scipy  matplotlib       sys exit

[python] python: sys is not defined

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