Python

This is a simple program that prints an Internet Draft (ID) or RFC.

 

Because of the difference between the number of lines on laser printers and line / dot-matrix printers, each “page” of the draft actually takes up 2 pages and you end up with lots of pages with just a one line footer.

This script tries to fix that by downloading the draft, converting it to a PDF and then printing it.

 

  This script prints an Internet Draft (or RFC). It does this by
  reading the file (possibly first fetching it from the Internet),
  converting it to a PDF (and doing basic munging on it and then
  sending the PDF to lpr to actually do the printing.

  Usage:
    -F, --file <filename>  -- print this local file.
    -O, --outdir <dir>     -- save the converted PDF in this dir.
    -h, --help             -- this help.
    <url>                  -- fetch (and print) the file at the URL.
  Example:
      ./print_rfc_or_draft.py  http://tools.ietf.org/rfc/rfc5635.txt
         Fetches and prints RFC5635 from the ietf.org site and prints it.

      ./print_rfc_or_draft.py -F ~wkumari/docs/IETF/MyDrafts/deprecate-as-sets-00.txt
         Prints the local file called deprecate-as-sets-00.txt.

 

Source is: print_rfc_or_draft.py

I like the Python logging module, but for some reason I always have issues remembering how to set it up. This is my cheat sheet:

import logging
logger = logging.getLogger('App Name')
def SetupLogging():
logger.setLevel(logging.DEBUG)
#create console handler and set level to debug
ch = logging.StreamHandler()
ch.setLevel(logging.DEBUG)
#create formatter
# was:%(asctime)s - %(name)s - %(levelname)s: %(message)s" 
formatter = logging.Formatter("%(levelname)s(%(name)s): %(message)s")
#add formatter to ch
ch.setFormatter(formatter)
#add ch to logger
logger.addHandler(ch)
logger.error("Whoops, an error!")
logger.debug ("Doing something boring") 

The formatter options are:

%(name)s            Name of the logger (logging channel)
%(levelno)s         Numeric logging level for the message (DEBUG, INFO,
WARNING, ERROR, CRITICAL)
%(levelname)s       Text logging level for the message ("DEBUG", "INFO",
"WARNING", "ERROR", "CRITICAL")
%(pathname)s        Full pathname of the source file where the logging
call was issued (if available)
%(filename)s        Filename portion of pathname
%(module)s          Module (name portion of filename)
%(lineno)d          Source line number where the logging call was issued
(if available)
%(created)f         Time when the LogRecord was created (time.time()
return value)
%(asctime)s         Textual time when the LogRecord was created
%(msecs)d           Millisecond portion of the creation time
%(relativeCreated)d Time in milliseconds when the LogRecord was created,
relative to the time the logging module was loaded
(typically at application startup time)
%(thread)d          Thread ID (if available)
%(process)d         Process ID (if available)
%(message)s         The result of record.getMessage(), computed just as
the record is emitted

 

One of the standard Perl tricks is making a hash of arrays (pun intended!).

In Python this is a little trickier.

For example, you read in a file of the form: device location — you will often need to to something like get all of the devices in New York, so you want to be able to do something like:

ny_devices = device_list["ny"]

The first thing you try is:

(device, location) = line.split(" ")
device_list[location].append(device)

This dies with: KeyError: ‘ny’ — this is because the key “ny” doesn’t exist yet.

One way to deal with this is:

(device, location) = line.split(" ")
if location not in device_list:
# Add empty list for location
device_list[location] = []
device_list[location].append(device)

A much cleaner way to do this is:

device_list.setdefault(location,[]).append(device)