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The Python error “ValueError: I/O operation on closed file” happens when you try to do I/O operations (read, write, etc.) on a file that’s already been closed.
Here’s what the error looks like:
Traceback (most recent call last):
File "/dwd/app.py", line 2, in
for line in file:
ValueError: I/O operation on closed file.
Incorrect indentation can cause the "ValueError: I/O operation on closed file" error when working with files in Python. Below are two scenarios leading to this error.
Scenario #1: closing the file inside a loop: Imagine you have a loop that reads data from a file.
However, you unintentionally close the file at the same indentation level as the loop, making it part of the loop.
As a result, when you try to read the second line of the file, you'll get the error because the file was closed in the first iteration.
file=open('data.txt','r')forlineinfile:print(line)# file is closed here
file.close()Enter fullscreen modeExit fullscreen mode
In the above code, since file.close() is indented within the loop (by mistake), the file is closed prematurely, causing the error.
To fix this issue, move the file.close() outside the loop, and you'll be good to go:
file=open('data.txt','r')forlineinfile:print(line)# Closing the file after the loop finishes
file.close()Enter fullscreen modeExit fullscreen mode
Scenario #2: Using the with statement: As you probably know, when you open a file using the with statement, you won't have to close the file at the end. Python automatically closes the file for you once the execution block finishes executing.
That said, if you have an I/O operation outside the with block, you'll run into the error since the file is closed.
Imagine we're trying to read a CSV file using the with open('...') syntax:
To check whether a file is closed, you can use the closed attribute of the respective file object. The closed attribute contains a boolean value indicating whether the file is open or closed.
Here's an example:
file=open('example.txt','r')print(file.closed)# False
file.close()print(file.closed)# True
Enter fullscreen modeExit fullscreen mode
The Python error "ValueError: I/O operation on closed file" typically occurs when a file is closed prematurely or due to incorrect indentation.
It's a simple rule; Just ensure the code that closes the file is executed after the I/O operations.
Alright, I think it does it! I hope you found this quick guide helpful.
Thanks for reading.
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