how to set an attribute in a nested object in Python?

Question

I'm making my first attempts at Python.

I need to loop over a log, parse log entries and then update an object, which includes nested objects for machines listed in the log.

This is what I have:

import re
format_pat= re.compile( 
    r"(?P<host>(?:[\d\.]|[\da-fA-F:])+)\s" 
    r"(?P<identity>\S*)\s" 
    r"(?P<user>\S*)\s"
    r"\[(?P<time>.*?)\]\s"
    r'"(?P<request>.*?)"\s'
    r"(?P<status>\d+)\s"
    r"(?P<bytes>\S*)\s"
    r'"(?P<referer>.*?)"\s'
    r'"(?P<user_agent>.*?)"\s*' 
)

from json import JSONEncoder
class MyEncoder(JSONEncoder):
    def default(self, o):
      return o.__dict__ 

# JSON response object
class ResponseObject(object):
    def __init__(self, dict):
      self.__dict__ = dict


# check for JSON response object
try:
    obj
except NameError:
    obj = ResponseObject({})

test = ['2001:470:1f14:169:15f3:824f:8a61:7b59 - SOFTINST [14/Nov/2012:09:32:31 +0100] "POST /setComputer HTTP/1.1" 200 4 "-" "-" 102356']

# log loop
for line in test:
  try:
    # try to create object from log entry
    m = format_pat.match(line)
    if m:
      res = m.groupdict()
      res["status"] = int(res["status"])

      # register machine if not done
      if not hasattr(obj, res["user"]):
        setattr(obj, res["user"], {"downtime":"0","flag":"false","downstart":"0","init":res["time"],"last":"","uptime":"","downtime":"","totaltime":""})


      machine = getattr(obj, res["user"])
      flag = machine["flag"]
      start = machine["downstart"]
      down = machine["downtime"]
      last = machine["last"]

      print "done"
      # set last
      last = res["time"]

      # PROBLEM this does not work
      setattr(machine, last, res["time"])
      print machine

    else:
      print "nope"
  except:
      print "nope base"

print MyEncoder().encode(obj)

The error I'm getting when trying to setattr() is

AttributeError: 'dict' object has no attribute ''

but I was afraid it was not as easy as this...

Question:
How do I update the last value in my nested object using 'setattr'? Or is there another way to update nested object attributes?

"...but I was afraid it was not as easy as this..."? It's actually easier than you were thinking. Sounds like it would help to familiarize yourself with Python data structures such as the dictionary. — John Y
– John Y, Commented Mar 5, 2013 at 17:48

Fábio Diniz · Accepted Answer · 2013-03-05 16:21:31Z

1

I think you need to do this:

setattr(machine, 'last', res["time"])

As setattr needs a string of the name of the attribute to be set

answered Mar 5, 2013 at 16:21

Fábio Diniz

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5 Comments

frequent Over a year ago

doesn't seem to work. Also I can use setattr further up in the code with a res["user"]

Fábio Diniz Over a year ago

@frequeent But what do you want? You want machine to have an attribute named last, or you want it to have an attribute which name is inside the variable last?

frequent Over a year ago

machine should have an attribute last with the time of the log entry

Fábio Diniz Over a year ago

@frequent Ok then you need to do exactly what is in my answer, what error are you getting?

frequent Over a year ago

it's still the same error ’AttributeError: 'dict' object has no attribute 'last'’. Your answer makes sense though. I don't understand why it's not working.

mike · Accepted Answer · 2013-03-05 17:13:26Z

1

Do not use setattr. Just assign a value to the "last" key for each machine dictionary.

(actually you answered your own question!)

answered Mar 5, 2013 at 17:13

mike

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Comments

frequent · Accepted Answer · 2013-03-05 16:39:07Z

0

I don't understand why, but I can set the value of last like this:

  print machine
  print machine["last"]
  print res["time"]

  # this works
  machine["last"] = res["time"]

  print machine

If someone can explain, would be nice :-)

answered Mar 5, 2013 at 16:39

frequent

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1 Comment

mike Over a year ago

machine is a dict. That's why you can set the value of "last" key.

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