Python - Beginner Level - User input and while Loop combination

Question

I have did a little research around "Google", "YouTube", "Facebook" and "Stack Overflow" and I haven't found what I was looking for. So, I need your guidance. :)

I want program to ask user input "PASSWORD" and every time user inputs wrong password the program asks password again, and again, and again until user types the correct password. Let's say that the password is as simple as "abc123".

So, I start the program and it asks to input: "PASSWORD: ". If user types "abc123" then program prints "GOOD PASSWORD". If user types anything what is not "abc123" then program prints "BAD PASSWORD". As simple as that.. for now.

My best attempt:

#SECTION1_ASKING
passwordInput=input('PASSWORD: ')
password='abc123'
while password == passwordInput:
    print('GOOD PASSWORD')
    break 
else:
    print('BAD PASSWORD')
    passwordInput=input('PASSWORD: ')

#SECTION2_RE-ASKING
while False:
    while password == paswordInput:
        print('GOOD PASSWORD')
    else:
        print('BAD PASSWORD')
        passwordInput=input('PASSWORD: ')

but I either make password asked once or twice or I stuck in Infinite while Loop.

You say two answers both worked, but one used raw_input(), which is Python 2, and one used input(), which is Python 3 (the Python 2 version of input() has a different use). Which version of Python are you using? — cdarke
– cdarke, Commented Mar 10, 2018 at 8:23
while and for are looping constructs, it seems you are mistaking them with if or at least mixing those up, because they all can be combined with else. BTW, one advise: Write a plan in plain language first, so that anyone could understand it and follow it even without any programming knowledge. Keep this plan in the comments of your code. — Ulrich Eckhardt
– Ulrich Eckhardt, Commented Mar 10, 2018 at 8:23
I tried them both. I am using Python 3.x. I know that "raw_input()" is "input()" in Python 3.x, so I changed that part before I ran the code. — simeon9446
– simeon9446, Commented Mar 10, 2018 at 8:25
Please read How do I ask a good question?. You can watch the execution of small programs in a debugger to understand, what went wrong. There are online tools for this as well like PythonTutor — Mr. T
– Mr. T, Commented Mar 10, 2018 at 8:25
Well, for what I understand as a beginner, if runs code for once, while runs code over and over again, for runs code certain amount of times, and else just runs code instead of condition that is set on if, while or for code. Since I have an answer of my issue I going to analyze my mistake deeper. I feel that I need to practice more on these(if, while, for) and get comfortable using them before I move on. — simeon9446
– simeon9446, Commented Mar 10, 2018 at 8:43

Omi Harjani · Accepted Answer · 2018-03-10 08:13:58Z

2

Try this:

passwordInput=raw_input('PASSWORD: ')
password='abc123'
while True:
    if password == passwordInput:
        print('GOOD PASSWORD')
        break 
    else:
        print('BAD PASSWORD')
        passwordInput=raw_input('PASSWORD: ')

answered Mar 10, 2018 at 8:13

Omi Harjani

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1 Comment

Omi Harjani Over a year ago

Your welcome :) @simeon9446 kindly mark it as the answer if it solves your query

Prakash Palnati · Accepted Answer · 2018-03-10 08:14:31Z

1

You can do as below in few lines.

password='abc123'
while(True):
    passwordInput=input('PASSWORD: ')
    if(passwordInput==password):
        print("Good password")
        break
    else:
        print("Bad password")

answered Mar 10, 2018 at 8:14

Prakash Palnati

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3 Comments

ifconfig Over a year ago

@simeon9446 Do you now know why your code didn't behave like you wanted it to?

cdarke Over a year ago

Why the parentheses around the conditions?

simeon9446 Over a year ago

@ifconfig Honestly, not really. It's like what I though that the program would do and what the program actually did went in similar but not exact direction. Whose fault - mine, because I gave wrong instructions to the program. Why? Because I lack knowledge and understanding. I am really "raw" in Python (several days of actual usage) :) Now I'm using PythonTutor to analyze mistakes, and learn.

cdarke · Accepted Answer · 2018-03-10 09:03:20Z

0

Here is my solution:

password = 'abc123'

while True:

    passwordInput = input('PASSWORD: ')

    if password == passwordInput:
        print('GOOD PASSWORD')
        break
    else:
        print('BAD PASSWORD')

How does that differ from yours? For a start you can see that I only have one call to input(), that's generally a good idea because then you only need to check the password in one place. Notice that I use if instead of while for the test.

In your second example you have while False:. Can this ever be True? No, so it won't get executed.

Notice as well that I use more whitespace. That does not slow the program down, it makes it easier to read. See also PEP008

Now you have it working, just for fun, consider an improvement. Normally you don't want the password to be visible when it is typed, but there's a module for that: getpass - it's part of the standard library so you don't need to download anything.

Add import getpass to the top of your script. Instead of input use getpass.getpass, in the same place in the program, with the same parameters. Now it won't echo the password entered by the user.

getpass is the module name, getpass is also a function name, so getpass.getpass('PASSWORD: ') means execute the getpass() function in the getpass module. We use lots of modules in Python, so its worth getting used to using them. You can find the documentation here, note there is also a getpass.getuser() to play with.

edited Mar 10, 2018 at 9:03

answered Mar 10, 2018 at 8:42

cdarke

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3 Comments

simeon9446 Over a year ago

Oh..wow! That's really impressive. How about allowing to enter bad password certain amount of times? Is that very complex to do?

cdarke Over a year ago

No, that's simple. Just initialise a count variable to zero at the start, then increment it (count += 1) each time you ask for the password. You then need an extra check (if) to see if the limit is exceeded. More or less a Python 101 exercise.

cdarke Over a year ago

By the way, next time you ask a question here consider if you really need that first paragraph. It doesn't add anything and does not make people more willing to help. What makes people help is to show the effort you tried yourself, which you did.

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