python 基礎（實例1——登陸小游戲）

一個簡單的登陸小游戲，輸入用戶名和密碼，如果和user_passwd.txt中內容匹配，則打印“welcome to login...”，如果三次輸入錯誤則將該用戶列入黑名單，無法再用該用戶名登陸。

1.python 對.txt文件的操作

　　a.python對文件的讀取

with open('user_passwd.txt') as f:
    lines = f.readlines()
    for line in lines:
        print(line)

　　b.pyhton對文件的寫入

with open('user_passwd.txt','a') as f:
    f.write(str)

2.split() 函數

　　當拿到文件的一行是往往需要對其進行切割才能得到我們想要的字段，split()函數會返回一個列表

　　str.split(s,[number_1])[number_2]

　　parameter s：切割點

　　parameter number_1: 切割段數

　　parameter number_2: 取切割后的列表的第number_2個元素

登陸小游戲代碼實現

flag = 0
for i in range(3):
    if flag == 1:
        break
    username = input("name:")
    passwd = input("password:")
    with open('black_list.txt') as f:     #is username in black_list
        lines = f.readlines()
        for line in lines:
            if username+'\n' == line:
                print("sorry, you are in black_list!")
                exit(0)      #exit
    with open('user_passwd.txt') as f:        # not in black_list
        lines = f.readlines()
        for line in lines:
            str_1 = line.split(',')[0]
            str_2 = line.split(',')[1]
            if username == str_1 and passwd + '\n' == str_2:
                print("welcome to login...")
                flag = 1
                break
        else:
            print("username or password is not correct!")
    if i == 2 and flag == 0:       # write in black_list
        with open('black_list.txt','a') as f:
            f.write(username)
            f.write('\n')