Asking the user for an input until but the answer is not valid.

[Hafiz75]

So im working on a program and what the program to ask the user to input a file name and if the file name does not exist it should say invalid input please try again. Then it should display the input part again until the file is found. How would i make the program re ask the question. I've put the code below. I would really appreciate if someone could help me figure out how i would go around this problem. 

userinput= input("Whats your File Called? \n" )
            confile=userinput+".txt"
            def main():
                f=open(confile, "r")
                if f.mode == 'r':
                   contents = f.read()
                   print(contents)
            if __name__== "__main__":
              main()

 

[79wjd]

Put the code requesting and checking the input in a while loop.

 

You'll need to check that the file exists (os.path.exists(FILENAME)) or catch an exception from opening a non-existent file.

# while CONDITION:

    # Input

    # If input == ____

         break

[Hafiz75]

Just now, 79wjd said:

Put the code requesting and checking the input in a while loop.

I dont understand what you mean?

 

[Hafiz75]

1 minute ago, 79wjd said:

Put the code requesting and checking the input in a while loop.

 

 

# while CONDITION:

    # Input

    # If input == ____

         break

 

So you want me to add a while loop to my code?

[79wjd]

2 minutes ago, Safeer Hafiz said:

I dont understand what you mean?

 

while True:

     user_input = input("Input filename")

     if os.path.exists(user_input):

         break

f = open(user_input)

[Hafiz75]

Still get an error Message

            while True:
                userinput= input("Whats your File Called? \n" )
                confile=userinput+".txt"
                def main():
                    f=open(confile, "r")
                    if f.mode == 'r':
                       contents = f.read()
                       print(contents)
                if __name__== "__main__":
                  main()
                if os.path.exists(userinput):
                    break
            f = open(userinput)
            

 

[Hafiz75]

6 minutes ago, 79wjd said:

while True:

     user_input = input("Input filename")

     if os.path.exists(user_input):

         break

f = open(user_input)

Any ideas why i get an error message

[79wjd]

5 minutes ago, Safeer Hafiz said:

Still get an error Message

            while True:
                userinput= input("Whats your File Called? \n" )
                confile=userinput+".txt"
                def main():
                    f=open(confile, "r")
                    if f.mode == 'r':
                       contents = f.read()
                       print(contents)
                if __name__== "__main__":
                  main()
                if os.path.exists(userinput):
                    break
            f = open(userinput)
            

 

import os

def main():
    while True:
        user_input = input("Input filename\n")
        filename = user_input + ".txt"
        if os.path.exists(filename):
            with open(filename, 'r') as f:
                contents = f.read()
                print(contents)
                break

if __name__ == '__main__':
    main()

[Hafiz75]

Just now, 79wjd said:

import os

def main():
    while True:
        user_input = input("Input filename\n")
        filename = user_input + ".txt"
        if os.path.exists(filename):
            break
    with open(filename, 'r') as f:
        contents = f.read()
        print(contents)

if __name__ == '__main__':
	main()

What is this. What does it do. Please could you talk and explain to me. Thanks

[Hafiz75]

6 minutes ago, 79wjd said:

import os

def main():
    while True:
        user_input = input("Input filename\n")
        filename = user_input + ".txt"
        if os.path.exists(filename):
            with open(filename, 'r') as f:
                contents = f.read()
                print(contents)
                break

if __name__ == '__main__':
    main()

It still gives and error

 

[79wjd]

6 minutes ago, Safeer Hafiz said:

What is this. What does it do. Please could you talk and explain to me. Thanks

When you run the program, it will go into the main function, prompt the user for input, if the input is a valid file then it will open and print the file. Otherwise will it re-prompt the user for input.

1 minute ago, Safeer Hafiz said:

It still gives and error

 

What error?

[Hafiz75]

1 minute ago, 79wjd said:

What error?

So when i pasted the code you made. It gave me an error

[79wjd]

Just now, Safeer Hafiz said:

So when i pasted the code you made. It gave me an error

What is the error?

[Hafiz75]

unexpected indentation. Plus is there a way to just keep my code and not change it all.

[Hafiz75]

1 minute ago, 79wjd said:

What is the error?

unexpected indentation

 

[79wjd]

Just now, Safeer Hafiz said:

unexpected indentation.

You need to fix the indentation somewhere. It tells you what line has the wrong indentation. Just correct it. 

Just now, Safeer Hafiz said:

Plus is there a way to just keep my code and not change it all.

Considering your code wasn't valid, no. There are many ways to do it, but the way you originally had it was wrong.

[Hafiz75]

Just now, 79wjd said:

You need to fix the indentation somewhere. It tells you what line has the wrong indentation. Just correct it. 

Considering your code wasn't valid, no. There are many ways to do it, but the way you originally had it was wrong.

But it was valid. Everything worked. Its just that if the user imputed a file that didn't exist it would just display an error. 

[79wjd]

5 minutes ago, Safeer Hafiz said:

But it was valid. Everything worked. Its just that if the user imputed a file that didn't exist it would just display an error. 

You need to add a while loop. If you really wanted then you could put the while loop (with the input request) outside of main (and all functions) like you had, but that's a really horrible coding practice.

 

import os

while True:

    user_input = input("Input filename\n")

    if os.path.exists(user_input):

        filename = user_input + ".txt"

        break

def main():

    f = open(filename, 'r')

    contents = f.read()

    print(contents)

    f.close()

if __name__ == '__main__':

    main()

[Hafiz75]

54 minutes ago, 79wjd said:

You need to add a while loop. If you really wanted then you could put the while loop (with the input request) outside of main (and all functions) like you had, but that's a really horrible coding practice.

 

import os

while True:

    user_input = input("Input filename\n")

    if os.path.exists(user_input):

        filename = user_input + ".txt"

        break

def main():

    f = open(filename, 'r')

    contents = f.read()

    print(contents)

    f.close()

if __name__ == '__main__':

    main()

Its not like i want it to look professional. I just want the program to work in the simplest way. 

[Hafiz75]

56 minutes ago, 79wjd said:

You need to add a while loop. If you really wanted then you could put the while loop (with the input request) outside of main (and all functions) like you had, but that's a really horrible coding practice.

 

import os

while True:

    user_input = input("Input filename\n")

    if os.path.exists(user_input):

        filename = user_input + ".txt"

        break

def main():

    f = open(filename, 'r')

    contents = f.read()

    print(contents)

    f.close()

if __name__ == '__main__':

    main()

Ok so the program runs now but when i enter the file name it just says input file name again. And keeps saying input file name

 

[79wjd]

5 minutes ago, Safeer Hafiz said:

Ok so the program runs now but when i enter the file name it just says input file name again. And keeps saying input file name

 

Then

if os.path.exists(filename)

is never evaluating to true. Are you sure you're entering the filename correctly?

 

If the directory looks like:

• Dir
  • script.py
  • file.txt

and you're running it from within Dir. (e.g. `python script.py`), then you would need to enter `file`. If you were running it from a different directory (e.g. `python PATH_TO_SCRIPT/script.py`), then you would need to enter 'PATH_TO_FILE/file`.

[Hafiz75]

1 hour ago, 79wjd said:

Then

 

if os.path.exists(filename)

 

is never evaluating to true. Are you sure you're entering the filename correctly?

 

If the directory looks like:

• Dir
  • script.py
  • file.txt

and you're running it from within Dir. (e.g. `python script.py`), then you would need to enter `file`. If you were running it from a different directory (e.g. `python PATH_TO_SCRIPT/script.py`), then you would need to enter 'PATH_TO_FILE/file`.

i have entered correct name of file. Still does not work

 

[79wjd]

14 minutes ago, Safeer Hafiz said:

i have entered correct name of file. Still does not work

 

Make it 

filename = user_input + '.txt'

if os.path.exists(filename):