Using shelve for good, not for evil

using_shelve.py

import os, shelve

# Get the current module (for its namespace, so we can fill it with variables)
import sys
thismodule = sys.modules[__name__]

# Get the hidden directory holding our persistence files
persistenceDirectory = os.path.expanduser("~/.mySecretData/") # The directory for our persistent data
os.system("mkdir -p " + persistenceDirectory) # Make sure the directory exists
pathToStateFile = os.path.join(persistenceDirectory, "stateVariables.db") # a persistent set of variables
state = shelve.open(pathToStateFile, flag='c') # opens the state file if it doesn't exist

# If we haven't set the state variables before, do it here.
# I also like this method, because it lists everything that
# we're tracking, and the suggested values/ranges that the variables should take.
if not state.has_key('defaults_set'):
	state['cropModeIsOn'] = False
	state['boxCenterModeIsOn'] = False
	state['drawCropRectangle'] = False
	state['drawCrosshairs'] = False
	state['upperLeft'] = (0,0)
	state['lowerRight'] = (0,0)
	state['boxCenter'] = (0,0)

	state['defaults_set'] = True
	

# Distribute out the state variables to the module
for key, value in zip(state.keys(), state.values()):
	setattr(thismodule, key, value)


# All of the wonderful things that your program does, well, they happen here
# ================================================
print drawCropRectangle # first time you run this, this'll print False. Second time, it'll print True.
drawCropRectangle = True
# ================================================


# Reclaim the state variables from the module
for key, value in zip(state.keys(), state.values()):
	state[key] = getattr(thismodule, key)



# Note that you can replace "thismodule" with a class. 
# There might be an even fancier way to do this by aliasing the dictionary variables into the desired
# namespace, but I don't know how to do that. I also don't know if it's a safe/good/easy idea.