NoneType Error on Instance Variables

Question

I'm having a bit of an issue. For some reason, this class I'm trying to put together is throwing a NoneType error when, for all intents and purposes it should be responding properly as far as I can tell.

import re
import subprocess

class progEnv( object ) :

    hostName_regex = re.compile( '[a-z][a-z]prog[a-z][a-z][a-z]\d\d' )
    hostDomain_regex = re.compile( '(prod|dev|qa1|stag)\.company\.net' )
    hostNum_regex = re.compile( '[a-z][a-z]prog[a-z][a-z][a-z](\d\d)' )
    hostPrefix_regex = re.compile( '\w\wprog' )
    hostTier_regex = re.compile( '(web|app)' )
    hostId_regex = re.compile( '[a-z][a-z]prog[a-z][a-z][a-z]\d\d([a-z])' )
    hostEnv_regex = re.compile( '(prod|dev|qa1|stag)' )

    def __init__( self ) :
        self.hostnameProc = subprocess.Popen( 'hostname', stdout=subprocess.PIPE )
        self.fqdn = self.hostnameProc.stdout.read()
        self.hostName = self.hostName_regex.search( self.fqdn )
        self.hostDomain = self.hostDomain_regex.search( self.fqdn )
        self.hostNum = self.hostNum_regex.search( self.hostName.group() )
        self.hostPrefix = self.hostPrefix_regex.search( self.hostName.group() )
        self.hostTier = self.hostTier_regex.search( self.hostName.group() )
        self.hostId = self.hostId_regex.search( self.hostName.group() )
        self.hostEnv = self.hostEnv_regex.search( self.hostName.group() )

When I instantiate the progEnv class the program fails on the call to self.hostName.group() with an error of:

Traceback (most recent call last):
  File "./test.py", line 5, in <module>
    env = prog_env.progEnv()
  File "/prog/eclipse/workspace/PROG Management Command/prog_env.py", line 28, in __init__
    self.hostNum = self.hostNum_regex.search( self.hostName.group() )
AttributeError: 'NoneType' object has no attribute 'group'

Any thoughts on what is happening?

Tim Pietzcker · Accepted Answer · 2012-01-10 12:22:45Z

3

This means that the regex didn't match, so self.hostName_regex.search(self.fqdn) returned None. And of course you can't use the .group() method on None.

answered Jan 10, 2012 at 12:22

Tim Pietzcker

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1 Comment

Drahkar Over a year ago

You were the first to respond and I just realized exactly what was happening. Time to take a moment and facepalm. I just realized the reason it is throwing the error is because I'm running it in a server that doesn't match the regex scheme. Ugh. Thanks for the help!

Duncan · Accepted Answer · 2012-01-10 12:24:05Z

0

The error message says that you are trying to access the attribute group of None. From the code line that is displayed that means self.hostName must be None. The regex search you used to initialise self.hostName must have failed to match anything.

BTW, you seem to not fully understand the error message. It isn't "throwing a NoneType error", it is throwing an AttributeError: the error message for an AttributeError shows you the type of the object and the type of None is NoneType.

answered Jan 10, 2012 at 12:24

Duncan

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Comments

simplyharsh · Accepted Answer · 2012-01-10 12:30:15Z

0

self.hostName = self.hostName_regex.search( self.fqdn )

This line sets the value of self.hostName to None, when self.fqdn is not matched by regex. Which is causing the error. Change the dependent lines to something like,

self.hostNum = self.hostName and self.hostNum_regex.search( self.hostName.group() )

just to check self.hostName before using its group method.

edited Jan 10, 2012 at 12:30

answered Jan 10, 2012 at 12:24

simplyharsh

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