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?

Answer 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()

• Argentum: data = [int(line.strip()) for line in f.readlines()] # [1, 2, 3] ValueError: invalid literal for int() with base 10: ''
• flevinkelming: @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: Thank so you freaking much! You have saved my day!
• flevinkelming: @PythonGirl glad I could help!

Answer 2

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

• Argentum: It only tells me that "data is not defined"
• Eliethesaiyan: Do you see on the top that data is declared as data=[],right on the top of my codes
• flevinkelming: You don't need to close the file when using a context manager. Nor is it necessary to open the file twice.
• Eliethesaiyan: @flevinkelming,true,i forgot
• Argentum: tells me: TypeError: write() argument must be str, not int

Answer 3

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)

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