why i can not delete my email with imaplib?

[elearn]

I have a gmail account 'xxx at gmail.com' which subscripted python 
maillist. I want to delete any emails which is sent to 
python-list at python.org .

|import  imaplib
user="xxx"
password="yyyyyy"
con=imaplib.IMAP4_SSL('imap.gmail.com')
con.login(user,password)
con.select('[Gmail]/&YkBnCZCuTvY-')
type,  data=  con.search(None,  "All")
type1,  data1=  con.search(None,  '(TO "python-list at python.org")')
ids_all=  set(data[0].split())
ids1=set(data1[0].split())

ids_deleted=set(ids_all-ids1)

for  numin  ids_deleted:
    con.store(num,  '+FLAGS',  '\\Deleted')


con.expunge()|

When i open my gmail with thunderbird ,the emails which are sent to 
python-list at python.org are still in my gmail,Why i can't delete them?

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