如何操作 CSV 数据？

Question

我正在尝试制作一个银行程序，您现在可以选择更改选项“2”中的密码。我尝试这样做但无济于事。谁能告诉我如何更改密码存储在“store.txt”的第 2 行。
示例：
这是我存储在文件“store.txt”中的数据

hello,me,0
bye,you,0

我要做的是将用户名“hello”的密码更改为“yolo”。我该怎么做？
这是我的代码：

import csv
run=True
while run==True:
    print "1)Create a new account"
    print "2) Change Password"
    choice=input("Enter your choice over here: ")
    #This part takes the input from the user and then stores it in 'store.txt'
    if choice==1:
        a=input("Enter how many people to register: ")
        for i in range(0,a) :
            #Stores username and password
            a=raw_input("Enter username: ")
            b=raw_input("Enter password: ")
            c=0
            #If username already exists, stop the process.
            with open ('store.txt','r') as store:
                reader = csv.reader(store)
                for row in reader:
                    if a==row[0]:
                        print "User already exists in our database , please try again."
                        break
            store.close()
            #If username is not there , write it down to store.txt
            with open ('store.txt','a') as store:
                storeWriter=csv.writer(store)
                storeWriter.writerow([a,b,c])
            store.close()

    if choice==2:
        print "Change password" 

Answer 1

要替换文件中的值：

with open('store.txt','r') as f:
    reader = list(csv.reader(f))
    for row in reader:
        row[1] = "some-new-value"

with open('store.txt','w') as f:
    wr = csv.writer(f)
    for row in reader:
        wr.writerow(row)

还有很多方法可以改进你的代码：

• 在“==”和“=”等运算符周围包含空格会更好（一个很好的资源：@​​987654321@）
• 如果您使用with 块，则不需要close() 您的文件。 with 会自动关闭您的文件。
• 您应该包含一些会破坏while 循环的条件；否则它将无限循环。
• 您的条件if 语句是错误的。你想要这样的伪代码：if username exists: print "some message" else: open file and append line