本次將學(xué)習(xí)如何編寫一個(gè)登錄接口小程序。

具體的需求

實(shí)現(xiàn)一個(gè)登錄接口，用戶輸入賬戶密碼即可看到歡迎語句，當(dāng)三次輸入密碼錯(cuò)誤時(shí)，則該帳號(hào)被鎖定。
鎖定的意義是，下次使用該賬戶登錄時(shí)，將無法成功登錄。

思路

因?yàn)樾枨笥写螖?shù)限制，所以需要有一個(gè)計(jì)數(shù)變量，同時(shí)可能還需要用到while和if語句。
需求提到被鎖定的帳號(hào)在程序下一次啟動(dòng)時(shí)仍然記住，眾所周知，python有內(nèi)存回收機(jī)制，程序在結(jié)束之后，所有列表、變量會(huì)從內(nèi)存中抹去，這就需要有一個(gè)文件來存放這些被鎖定的帳號(hào)。
我們需要使用python的open方法來寫入文件，可以將鎖定帳號(hào)寫入文件，可以命名為blacklist.txt之類的。

blacklist=open("blacklist.txt","w")

此外，需求還需要實(shí)現(xiàn)多用戶的登錄操作，這就需要我們建立一個(gè)用戶密碼的文件，可以命名為admin.txt，每次登錄需要從里面校驗(yàn)用戶名密碼是否正確。

passwd=open("admin.txt","r")

程序邏輯

我們接下來通過流程圖來把整個(gè)過程先梳理一遍：

login_port.png

實(shí)現(xiàn)

因?yàn)樯婕暗接脩裘艽a讀取，用戶名和用戶密碼的一個(gè)對(duì)應(yīng)。
拉入黑名單需要涉及文件寫入的操作，有點(diǎn)復(fù)雜。
可以先用list列表把問題簡(jiǎn)單化。
所以我先用列表代替文件，密碼先只有一個(gè)，寫死的。

初步實(shí)現(xiàn)

#owner:houyizhong
#version:demo

admin_name=["houyizhong","test"]
admin_passwd="137010116"
blacklist=["test"]

count = 0
while count < 3:
        username=input("Enter your username:")
        passwd=input("Enter your password:")
        if username not in admin_name:
                print("Sorry,your account is not exist!")
                continue
        elif username in blacklist:
                print ("Sorry you are in blacklist!")
                exit()
        else:
                if passwd != admin_passwd:
                        print("Sorry,enter your password again!")
                        count += 1
                else:
                        print("Welcome! {0}".format(username))
                        break
else:
        print("Sorry you are in blacklist!")
        blacklist.append(username)
        exit()

運(yùn)行這段代碼，可以看到：

[root@houyizhong ~]# python login.py 
Enter your username:houyizhong
Enter your password:137010116
Welcome! houyizhong

然后開始考慮實(shí)現(xiàn)文件的讀取，寫入操作。
最終實(shí)現(xiàn)代碼：

# -*- coding:utf-8 -*-
#owner:houyizhong
#version1.0

#創(chuàng)建列表
admin_name=[]
admin_passwd=[]
blacklist=[]

#讀取用戶文件
passwd_file=open("admin.txt","r")
admin_list=passwd_file.readlines()
passwd_file.close()

#提取出用戶名，密碼，添加進(jìn)列表
for i in range(len(admin_list)):
        admin_parts=admin_list[i]
        admin_passwd.append(admin_parts.strip())
        admin_part=admin_parts.split(":")
        admin_name.append(admin_part[0])

#讀取黑名單文件
blacklist_file=open("blacklist.txt","r")
blacklist_raw=blacklist_file.readlines()
blacklist_file.close()

#提取黑名單用戶名
for i in range(len(blacklist_raw)):
        blacklist_value=blacklist_raw[i]
        blacklist.append(blacklist_value.strip())

count = 0

while count < 3:
        username=input("Enter your username:")
        passwd=input("Enter your password:")

        if username not in admin_name:
                print("Sorry,your account is not exist!")
                continue
        elif username in blacklist:
                print ("Sorry you are in blacklist!")
                exit()
        else:
                if ("{0}:{1}".format(username,passwd)) not in admin_passwd:
                        print("Sorry,enter your password again!")
                        count += 1
                else:
                        print("Welcome! {0}".format(username))
                        break
else:
        print("Sorry you are in blacklist!")
        blacklist_file=open("blacklist.txt","a")
        blacklist_file.write("{0}\n".format(username))
        blacklist_file.close()
        exit()

改進(jìn)

當(dāng)然這樣還不完美，還有一個(gè)小漏洞，就是這種判斷鎖定的是第三次用戶輸錯(cuò)時(shí)的賬戶，如果有人連續(xù)輸錯(cuò)兩次密碼，再第三次輸入別人的賬戶，故意輸錯(cuò)，就會(huì)導(dǎo)致別人的賬戶被鎖定，存在惡意攻擊的漏洞，請(qǐng)看如下演示：

[root@houyizhong pythonprobe]# python login.py
Enter your username:houyizhong
Enter your password:11111
Sorry,enter your password again!
Enter your username:houyizhong
Enter your password:11111
Sorry,enter your password again!
Enter your username:root
Enter your password:1111
Sorry,enter your password again!
Sorry you are in blacklist!
[root@houyizhong pythonprobe]# cat blacklist.txt
root

修正了一下之后，代碼是這樣的，加了一個(gè)while判斷，同時(shí)把輸入密碼的操作放在第二個(gè)循環(huán)里，這樣就避免了惡意鎖定別人的賬戶：

# -*- coding:utf-8 -*-
#owner:houyizhong
#version2.0

#創(chuàng)建列表
admin_name=[]
admin_passwd=[]
blacklist=[]

#讀取用戶文件
passwd_file=open("admin.txt","r")
admin_list=passwd_file.readlines()
passwd_file.close()

#提取出用戶名，密碼，添加進(jìn)列表
for i in range(len(admin_list)):
        admin_parts=admin_list[i]
        admin_passwd.append(admin_parts.strip())
        admin_part=admin_parts.split(":")
        admin_name.append(admin_part[0])

#讀取黑名單文件
blacklist_file=open("blacklist.txt","r")
blacklist_raw=blacklist_file.readlines()
blacklist_file.close()

#提取黑名單用戶名
for i in range(len(blacklist_raw)):
        blacklist_value=blacklist_raw[i]
        blacklist.append(blacklist_value.strip())

count = 0

while count < 3:
        username=input("Enter your username:")

        if username not in admin_name:
                print("Sorry,your account is not exist!")
                continue
        elif username in blacklist:
                print ("Sorry you are in blacklist!")
        else:
                pass

        while count < 3:
                passwd=input("Enter your password:")
                if ("{0}:{1}".format(username,passwd)) not in admin_passwd:
                        print("Sorry,enter your password again!")
                        count += 1
                else:
                        print("Welcome! {0}".format(username))
                        exit()

else:
        print("Sorry you are in blacklist!")
        blacklist_file=open("blacklist.txt","a")
        blacklist_file.write("{0}\n".format(username))
        blacklist_file.close()
        exit()

基本部分完成之后，我們?cè)賹?duì)程序優(yōu)化下，目前輸入密碼是明文的，我們可以用getpass模塊來解決這個(gè)問題，優(yōu)化的代碼示例如下：

# -*- coding:utf-8 -*-
#owner:houyizhong
#version2.0

import getpass

#創(chuàng)建列表
admin_name=[]
admin_passwd=[]
blacklist=[]

#讀取用戶文件
passwd_file=open("admin.txt","r")
admin_list=passwd_file.readlines()
passwd_file.close()

#提取出用戶名，密碼，添加進(jìn)列表
for i in range(len(admin_list)):
        admin_parts=admin_list[i]
        admin_passwd.append(admin_parts.strip())
        admin_part=admin_parts.split(":")
        admin_name.append(admin_part[0])

#讀取黑名單文件
blacklist_file=open("blacklist.txt","r")
blacklist_raw=blacklist_file.readlines()
blacklist_file.close()

#提取黑名單用戶名
for i in range(len(blacklist_raw)):
        blacklist_value=blacklist_raw[i]
        blacklist.append(blacklist_value.strip())

count = 0

while count < 3:
        username=input("Enter your username:")

        if username not in admin_name:
                print("Sorry,your account is not exist!")
                continue
        elif username in blacklist:
                print ("Sorry you are in blacklist!")
        else:
                pass

        while count < 3:
                passwd=getpass.getpass("Enter your password:")
                if ("{0}:{1}".format(username,passwd)) not in admin_passwd:
                        print("Sorry,enter your password again!")
                        count += 1
                else:
                        print("Welcome! {0}".format(username))
                        exit()

else:
        print("Sorry you are in blacklist!")
        blacklist_file=open("blacklist.txt","a")
        blacklist_file.write("{0}\n".format(username))
        blacklist_file.close()
        exit()

到目前為止，一個(gè)用列表和while，if語句判斷的登陸小程序就算完成了。

現(xiàn)在看來用列表來裝這些用戶名密碼什么的還是挺復(fù)雜的，要是用字典就更好了，另外寫入黑名單的操作可以做成def函數(shù)，這樣看起來更清晰，還可以重復(fù)調(diào)用，效率更高。

字典

將源程序中的列表做成字典的形式，用戶名對(duì)應(yīng)密碼，結(jié)構(gòu)更清晰?？梢岳米值?dict[username]=passwd 把用戶名的密碼存放，用dict[username]調(diào)用對(duì)應(yīng)用戶的密碼,同時(shí)加入了一個(gè)old_name的變量，用來判斷上一次輸入的username是否和這一次的一樣，不一樣則計(jì)數(shù)變量count重新開始計(jì)算。
實(shí)現(xiàn)代碼：

#-*- coding:utf-8 -*-
#version3.0
#owner:houyizhong

#create the list and dict
#admin_name=[]
admin_passwd={}
blacklist=[]

#read admin file
admin_file=open("admin.txt","r")
admin_list=admin_file.readlines()
admin_file.close()

#read admin username and password
for i in range(len(admin_list)):
    admin_parts=admin_list[i]
    admin_raw=admin_parts.strip()
    admin_part=admin_raw.split(':')
    name=admin_part[0]
    passwd=admin_part[1]
    admin_passwd[name]=passwd

print(admin_passwd)

#read blacklist file
blacklist_file=open("blacklist.txt","r")
blacklist_raw=blacklist_file.readlines()
blacklist_file.close()

#read blacklist username
for i in range(len(blacklist_raw)):
    blacklist_value=blacklist_raw[i]
    blacklist.append(blacklist_value.strip())

count = 0 
old_name=""

while count < 3:
    username=input("username:")
    if username != old_name:
        count = 0
    passwd=input("passwd:")
    old_name=username
    
    if username not in admin_passwd:
        print ("Sorry ,you account is not exist!")
        continue
    elif username in blacklist:
        print ("Sorry ,you are in the blacklist!")
        exit()
    else:
        if passwd != admin_passwd[username]:
            count += 1
            print("Sorry,you password is wrong.")
        else:
            print ("Welcome!{0}".format(username))
            break
else:
    print ("You are in blacklist now!")
    blacklist_file=open("blacklist.txt","a")
    blacklist_file.write("{0}\n".format(username))
    blacklist_file.close()
    exit()

實(shí)現(xiàn)效果：

[houyizhong@localhost py]$ python login.py 
username:test
passwd:
Sorry,you password is wrong.
username:test
passwd:
Sorry,you password is wrong.
username:root
passwd:
Sorry,you password is wrong.
username:root
passwd:
Welcome!root

好了，大功告成了，這一階段的學(xué)習(xí)就到這里啦~