python: Extracting info from a dictionary

teaching myself how to code and I need help

I'm trying to make sure the user inputs the right user name (credentials_U) and password (credentials_P)

DESIRED OUTPUT

• if they get both right it prints welcome
• if they only get the username right it prints wrong password
• if they get username wrong and or password wrong it prints incorrect and loops again.

CURRENT OUTPUT returns nothing

directory = {"ash":"123",}

def logon():
credentials_U = input("please input your username: ")
credentials_P = input("please input you password: ")
access = False

while access != True:
    if credentials_U in directory:
        if credentials_P in directory:      #true and true
            print ("welcome")
            access = True
            break


    elif credentials_U in directory:
        if credentials_P not in directory:       #true and false
            print ("incorrect password")
            logon()


    elif credentials_U not in directory:
        if credentials_P in directory:       #false and true
            print ("incorrect")
            logon()


    elif credentials_U not in directory:
        if credentials_P not in directory:      #false and false
            print ("incorrect")
            logon()

    else:
        print("incorrect details")
        logon()