python 新手，求解。。。。这是书上的一个例子，运行总是有问题，求各位大神帮忙看看！！！感激不尽。

#database.py
import sys,shelve
def store_person(db):
"""

Query user for data and store it in the shelf object
"""

pid = raw_input('Enter unique ID number:')
person = {}
person['name']=raw_input('Enter name:')
person['age']=raw_input('Enter age:')
person['phone']=raw_input('Enter phone:')

db[pid]=person
def lookup_person(db):
"""


Query user for ID and desired filed,and fecth the corresponding data form the shelf object
"""

pid = raw_input('Enter ID number')
filed = raw_input('What would you like to know?(name,age,phone)')
filed = filed.strip().lower()
print filed.capitalize() + ':',db[pid][filed]
def print_help():
print'The availabel command are:'
print'store: Store information about a person'
print'lookup: Lookup a person form a ID number'
print 'quit: Save changes and exit'
print'? : prints this message '
def enter_command():
cmd = raw_input('Enter command(? for help):')
cmd = cmd.strip().lower()
return cmd

def main():
database = shelve.open('C:\\database.dat ')
try:
while Ture:
cmd = enter_command()
if cmd =='store':
store_person(database)
elif cmd =='lookup':
lookup_person(database)
elif cmd =='?':
print_help
elif cmd =='quit':
return
finally:
database.close()

if __name__ == '__main__':
main()