如果其中一个以特定字符串开头，则在Python中读取连续两行

Question

I am currently trying to learn Python. I know some basics and I'm trying to practise by making a game. My code so far is:

import time
import datetime

now = datetime.datetime.now()

name = input('What is your name? >> ')
file = open("users.txt","+w")
file.write(name + ' started playing at: ' + now.strftime("%Y-%m-%d %H:%M") + '. \n')
file.close()

account = input('Do you have an account ' + name + '? >> ')
while(account != 'yes'):
    if(account == 'no'):
        break
    account = input('Sorry, I did not understand. Please input yes/no >> ')
if(account == 'yes'):
    login = input('Login >>')
    passwd = input('Password >>')
    if login in open('accounts.txt').read():
        if passwd in open('accounts.txt').read():
            print('Login Successful ' + login + '!')
        else:
            print('Password incorrect! The password you typed in is ' + passwd + '.')
    else:
            print('Login incorrect! The login you typed in is ' + login + '.')

As you probably noticed I am working on a login system. Now please ignore all the bugs and inefficient code etc. I want to focus on how I can get Python to check for a line in a .txt file and, if it's there, check the one below. My .txt file is:

loggn
pass
__________

I want to make the program multi-account. This is why I am using a .txt file. If you need me to clarify anything, please ask. Thankyou! :)

Answer 1

with open('filename') as f:
    for line in f:
        if line.startswith('something'):
            firstline = line.strip() # strip() removes whitespace surrounding the line
            secondline = next(f).strip() # f is an iterator, you can call the next object with next.

Answer 2

Store the results of "open('accounts.txt').read()" yourself, and iterate over them as an array - if you know what line number you are on, it is trivial to check the next. Assuming that every even numbered line is a login, and every odd numbered line is a password, you would have something like this:

success = False
# Storing the value in a variable keeps from reading the file twice
lines = open('account.txt').readlines()
# This removes the newlines at the end of each line
lines = [line.strip() for line in lines] 
# Iterate through the number of lines
for idx in range(0, len(lines)):
    # Skip password lines
    if idx % 2 != 0:
        continue
    # Check login
    if lines[idx] == login:
        # Check password
        if lines[idx + 1] == password:
            success = True
            break

if success:
    print('Login success!')
else:
    print('Login failure')

You may also consider changing your file format: using something that won't occur in the login name (such as a colon, unprintable ASCII character, tab, or similar) followed by the password for each line means you could use your original approach by just checking for (login + "\\t" + password) for each line, rather than having to worry about having two lines.