Python programming with file

Question

I need help with a problem concerning the code below.

with open ("Premier_League.txt", "r+") as f:
        i= int(input("Please put in your result! \n"))
        data = f.readlines()
        print(data)
        data[i] = int(data[i])+1
        f.seek(0) # <-- rewind to the beginning
        f.writelines(str(data))
        f.truncate() # <-- cut any leftovers from the old version
        print(data)
        data[i] = str(data)

For example if the file Premier_League.txt contains:

1
2
3

and as I run the program and choose i as 0 that gives me:

[2, '2\n', '3']

and saves it to the already existing file (and deletes the old content) But after that I cannot run the program again and it gives me this:

ValueError: invalid literal for int() with base 10: "[2, '2\\n', '3']"

My question is: How do I make the new file content suitable to go into the program again?

flevinkelming · Accepted Answer · 2017-07-19 10:29:04Z

1

I recommend this approach:

with open('Premier_League.txt', 'r+') as f:
    data = [int(line.strip()) for line in f.readlines()] # [1, 2, 3]
    f.seek(0)

    i = int(input("Please put in your result! \n"))

    data[i] += 1  # e.g. if i = 1, data now [1, 3, 3]

    for line in data:
        f.write(str(line) + "\n")

    f.truncate()

edited Jul 19, 2017 at 10:29

answered Jul 19, 2017 at 10:19

flevinkelming

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4 Comments

Argentum Over a year ago

data = [int(line.strip()) for line in f.readlines()] # [1, 2, 3] ValueError: invalid literal for int() with base 10: ''

flevinkelming Over a year ago

@PythonGirl make sure you reset your Premier_League.txt file... if it contains '2\\n' as in your question, you'll receive that error.

Argentum Over a year ago

Thank so you freaking much! You have saved my day!

flevinkelming Over a year ago

@PythonGirl glad I could help!

Eliethesaiyan · Accepted Answer · 2017-07-19 10:30:11Z

1

f readlines() read all content in a list as a string,if you want write back those contents as int

data=[]
with open ("Premier_League.txt", "r+") as f:
        i= int(input("Please put in your result! \n"))
        data = f.readlines()

with open ("Premier_League.txt", "w") as f:            
        for j in data:
            f.write(str(int(j)+1))
            #or do this to make it more clean,these lines are comments
            #j=int(j)+1
            #f.write(str(j))



         # <-- cut any leftovers from the old version
print(data)

Note that,once you open a file,if you don't close it,your written contents can be lost,whatever you want to do with data,your have to do it in the second writing method .Also notice the change from r to w in with open ("Premier_League.txt", "w") for writing

edited Jul 19, 2017 at 10:30

answered Jul 19, 2017 at 10:06

Eliethesaiyan

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5 Comments

Argentum Over a year ago

It only tells me that "data is not defined"

Eliethesaiyan Over a year ago

Do you see on the top that data is declared as data=[],right on the top of my codes

flevinkelming Over a year ago

You don't need to close the file when using a context manager. Nor is it necessary to open the file twice.

Eliethesaiyan Over a year ago

@flevinkelming,true,i forgot

Argentum Over a year ago

tells me: TypeError: write() argument must be str, not int

valentinarho · Accepted Answer · 2017-07-19 10:35:42Z

1

Following my solution:

with open ("Premier_League.txt", "r+") as f:
        i= int(input("Please put in your result! \n"))
        # here strip wrong chars from input 
        data = f.readlines()
        print(data)
        # here added the str(..) conversion
        data[i] = str(int(data[i].strip())+1) + '\n'
        f.seek(0) # <-- rewind to the beginning
        # the str(data) is wrong, data is a list!
        f.writelines(data)
        # I don't think this is necessary
        # f.truncate() # <-- cut any leftovers from the old version
        print(data)
        # i think this is not necessary
        # data[i] = str(data)

edited Jul 19, 2017 at 10:35

answered Jul 19, 2017 at 10:08

valentinarho

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2 Comments

Argentum Over a year ago

Hi I tried your solution (and put i=0) and this happened, file contained ['0', '1', '2', '3'], first run gave me ['1', '1', '2', '3'] which is exactly what I wanted!, the second run gave me ['22344', '4', ''] which is clearly wrong...

valentinarho Over a year ago

Oh I missed that writelines does not automatically add the newline char at the end of each element. I updated my answer.

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