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# Add general information below

FILENAME:

• ncreader.py

DESCRIPTION:

• Introduction to various python objects Python Seminar 13.09.2012

# for python objects naming conventions and style see PEP8: # http://www.python.org/dev/peps/pep-0008/

# If you use this file as a importable module for other programs than # the information below is useful to describe author = "A. U. Thor" version = "0.0" date = "0000/00/00"

import sys import os from optparse import OptionParser import Nio import numpy as np import matplotlib.pyplot as plt import pdb import cPickle as cP

# below is a simple class that provides some convenience functions class NcReader:

• As an example, this particular Class is basically

  • a set of convenience functions that are meant

    to speed up some of your routine work with NetCDF files

  def init(self, file_path):

  • Initialize object self.fpath = file_path self.ncfile = Nio.open_file(self.fpath) self.variables = self.ncfile.variables

  def printVars(self):

  • prints variables dictionary for i in self.variables:

    • print i
  def plotVar(self, var_name):

  • plots single 1d variable variable = self.ncfile.variables[var_name][:] plt.plot(variable) plt.show()

  def plot2dVar(self, *args, **kwargs):

  • plots multiple 2d variables # args is a tuple # kwargs is a keyworded dictionary for i in args:

    • try:
      • var = self.variables[i] print var[:].shape plt.imshow(self.variables[i][0,:])
      except:

      • raise #KeyError("variable %s not found" %i)

      if kwargs['colorbar'] == True:
      • plt.colorbar()
      plt.show()

# "parse_options" is meant to parse command line arguments and options # there can be unknown number of arguments, but options are predefined # mandatory arguments are actually options

def parse_options():

• Parse command line options and arguments

  usage = "usage: %prog [options] <input_files>"; version = "%prog 0.1" parser = OptionParser(usage) parser.add_option("-d", "--pdb_switch", dest = 'pdb_switch',

  • action = "store_true", default = "False")
  parser.add_option("-i", "--input_file", dest = 'input_file') (options, args) = parser.parse_args() return (options, args)

# It is a good practice to separate code execution and objects like classes # and functions # Main function is used for executing python code as a standalone program # def main():

• options, arguments = parse_options() input_file = options.input_file variables = arguments[:]

  a = NcReader(input_file) a.printVars() # keyworded arguments - normally used as options for fuctions # non keyworded arguments - just arguments a.plotVar('plev') a.plot2dVar(*variables, colorbar = True) # debugger? pdb_switch = options.pdb_switch

# The following structure is useful if # the code to be run as a standalone program AND a module which # can be imported in other python scripts if name == "main":

• main()