notstring.py

 #Given a string, return a new string where "not " has been added to the front. However, if the string already begins with "not", return the string unchanged.

#not_string('candy') - 'not candy'
#not_string('x') - 'not x'
#not_string('not bad')- 'not bad'

def not_string(str):
    if(str[:3]=='not'):
       return str
    else:
       return 'not '+str