How can I write data to file in the python program?

Question

I wrote a code to create a user and login but the created user will be in memory only till the program is running and when the program closes then the user gets destroyed. Now if I decide to store the username and password to a file, then how can I do so in the below python code.I just want to store it to a file not to read or compare it yet. And I just started learning Python so don't know anything advance or any tricky terms.

Edit: I am unable to write the username and password to the file.

users = {}
status = ""

f = open('E:\\login_try2.txt','w')

def displayMenu():
    status = input("Are you registered user? y/n/q ")
    if status == "y":
        oldUser()
    elif status == "n":
        newUser()
    elif status == "q":
        exitCode()

def exitCode():
    exit()

def newUser():
    username = input("Enter username: ")     
    f.write(username)

    if username in users:
        print("\nUsername already exists!\n")
    else:
        password = input("Create Password: ")
        users[username] = password
        f.write(password)
        print("\nUser created\n")

def oldUser():
    login = input("Enter username: ")
    passw = input("Enter password: ")

    if login in users and users[login] == passw:
        print("\nLogin Successful!\n")
    else:
        print("\nUser doesnt exist or wrong password!\n")

while status != "q":
    displayMenu()

f.close()

What's the problem you are seeing with your code? A problem statement and a code dump is nice, but it doesn't show us where we can help clarify a specific issue. — jpp, Jul 17 '18 at 16:57
Possible duplicate of https://stackoverflow.com/questions/1047318/easiest-way-to-persist-a-data-structure-to-a-file-in-python — tripleee, Jul 17 '18 at 17:02
You should use `with open(filename) as f` instead of opening and closing the file manually. See https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files. This might be the issue since your call to `f.close` never gets called — c2huc2hu, Jul 17 '18 at 17:05
Tried what? The linked question has half a dozen answers, and your code doesn't implement any one of them. — tripleee, Jul 17 '18 at 17:06
if I use `import pickle` then `pickle.dump(variable, file_name)`, I get `TypeError: write() argument must be str, not bytes` — , Jul 17 '18 at 17:09

score 1 · Answer 1 · answered Jul 17 '18 at 17:16

1

The problem is that your f.close() statement is only executed after exiting the application, so the data is not reliably flushed to the file.

Probably the easiest solution is to move f.close() to after f.write(password) in the newUser function.

answered Jul 17 '18 at 17:16

Chris

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score 0 · Answer 2 · answered Jul 17 '18 at 17:16

The answer was quite simple. The f.close() was not getting called due to which the program was not able to store data in the file. So I added f.close() in the def exitCode():

def exitCode():
    f.close()
    exit()

How can I write data to file in the python program?

2 Answers2