os.environ.example1.py

#!/usr/bin/env python


import os

def print_all():
    print "os.environ['myname']=%s" % (os.environ['myname']
                                       if 'myname' in os.environ else "None")
    os.system('env | grep myname')
    print

def delete_myname():

    if 'myname' in os.environ:
        os.environ.pop('myname')

print_all()

os.environ['myname'] = 'rfmonk'
print "-----------------------"
print_all()
delete_myname()
print_all()