python 3的新手并且在访问字典值时遇到问题

Question

I'm trying to make a simple login page using information stored in the dictionary. Everytime I enter the correct user name and password combination it falls back to the else statement- "sorry credentials not found in database". What am I doing wrong?

acc={"t":"000", "b":"123", "r":"456"}
p=input ("enter account name :")
pp=input ("enter account password :")
if p==dict.keys(acc) and pp==dict.values(acc):
 print ("access granted")
else:
 print ("sorry credentials not found in database")

Answer 1

The keys and values method return sequences of all keys and values, respectively. Neither will be equal to a single key or value.

if p in acc and pp == acc[p]:
    print("access granted")
else:
    print("sorry credentials not found in database")

Tangentially, dict.keys(acc) is a rather stilted way of writing acc.keys() (and likewise for acc.values() ).

Answer 2

dict.keys(acc) (same as acc.keys() ) gives you a list of all dictionary keys. A single login name is never equal to a list. What you need is to check if the login name P is in the dictionary and its value matches the stored password:

if acc.get(P, None) == Pp:

By the way, both P and Pp are bad identifiers.

Answer 3

Examine the return value of dict.keys(acc) .

>>> acc = {"t":"000", "b":"123", "r":"456"}
>>> P = input ("enter account name : ")
Tiddles
>>> p
'Tiddles'
>>> dict.keys(acc)
dict_keys(['t', 'b', 'r'])
>>> p == dict.keys(acc)
False

It's always going to be False?

You probably want something like this:

>>> acc = {"username": "Tiddles", "password": "12345"}
>>> p = input("enter account name: ")
Tiddles
>>> acc['username'] == p
True