ValueError : I/O operation on closed file
When I try to write to the file it reports the error:
6 Answers 6
Indent correctly; your for statement should be inside the with block:
Outside the with block, the file is closed.
Same error can raise by mixing: tabs + spaces.
I also have the same problem. Here is my previous code
Apparently, I shoud write the usersWriter instead of NodeWriter.
Below is my current code and it is working
Save data to a variable( file ), so you need a with .
I had this problem when I was using an undefined variable inside the with open(. ) as f: . I removed (or I defined outside) the undefined variable and the problem disappeared.
Another possible cause is the case when, after a round of copypasta, you end up reading two files and assign the same name to the two file handles, like the below. Note the nested with open statement.
The fix would then be to assign different variable names to the two file handles, e.g. f1 and f2 instead of both f .
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[Solved] ValueError: I/O operation on closed file
The i/o operations in Python are performed when the file is in an open state. So if we are trying to read or write into a file that is already closed state Python interpreter will raise the ValueError: I/O operation on closed file.
In this article, we will look at what is ValueError: I/O operation on closed file and how to resolve this error with examples.
ValueError: I/O operation on closed file
The best practice during file operations is to close the file as soon as we perform the operations with the file. It helps to free the resources such as memory and computing and also helps improve the overall performance. Once the file is closed, you can no longer access the file and perform read/write operations on that file.
- First, when you try, forget to indent the code in the with statement.
- Second, when you try to read/write to a file in a closed state.
- Third, when you close the file inside a for loop, accidentally
Let us look at an example where we can reproduce the issue.
Scenario 1 – Improper Indentation
We have a simple code to read the CSV file, which consists of employee data. First, we have imported the CSV library, and then we used a with statement to open the CSV file in a read mode,
Once the file is opened, we call the method csv.reader() to read the file contents and assign the contents into the read_csv variable.
Later, using the for loop, we iterated the file contents and printed each file row.
Let us run this code and see what happens.
Solution
The above code has returned ValueError because we tried to iterate the read_csv outside the with statement. The with statement acts as a file context, and once it’s executed, it will automatically close the file. Hence any file operation outside the with statement will lead to this error.
We can resolve the code by properly indenting our code and placing it inside the with statement context. But, first, let us look at the revised code.
Output
Scenario 2 – Accessing the closed file
It is the most common and best practice to use with statements for accessing the files. We can also access the file without using the with statement by just using the open() method as shown below.
Once the file is open, using the csv.reader() method we have read the contents of the file and assigned it to a variable read_csv .
Then, we closed the file as the contents are read and stored to a variable. Next, we iterate the read_csv variable using a for loop and print each row of the CSV file.
Let us execute the code and see what happens.
Output
Solution
The fix here is straightforward; we need to ensure that the file is closed after the for loop. The read_csv file holds a reference of the file object, and if we close the file, it will not be able to access the file and perform any I/O operations.
Let us fix the issue and execute the code.
Output
Scenario 3 – Closing the file inside a for loop
There could be another scenario where we do not correctly indent the code, which can lead to this issue.
For example, in the below code, we are opening the file and reading the file contents using csv.reader() method.
Next, using the for loop, we are iterating the CSV rows and printing each row. We have placed the file close() method inside the for loop accidentally, which will lead to an issue.
The loop executes and prints the first record successfully, and after that, it will close the file, and it won’t be able to access any other rows in the CSV.
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Output
Solution
We can resolve the issue by placing the close() statement outside the for loop. This will ensure that file contents are iterated and printed correctly, and after that, the file is closed.
Let us revise our code and execute it.
Output
Conclusion
The ValueError: I/O operation on closed file occurs if we are trying to perform the read or write operations on the file when it’s already in a closed state.
We can resolve the error by ensuring that read and write operations are performed when the file is open. If we use the with statement to open the file, we must ensure the code is indented correctly. Once the with statement is executed, the file is closed automatically. Hence any I/O operation performed outside the with statement will lead to a ValueError.
How To Solve “ValueError: I/O operation on closed file” In Python
The “ValueError: I/O operation on closed file” error in Python is a common error related to the file i/o operation. You can read the explanations below to have more knowledge about this error including cause and solutions.
Table of Contents
How does the “ValueError: I/O operation on closed file” error in Python happen?
This error happens due to the many following reasons:
Firstly, it might be because you are working on a closed file. If a file is open, you might not get the error. But if the file is closed and you are trying to write or read that file, you will get this error. For example:
Secondly, after working with long lines of code, you make the mistake of reading two files but assigning the same name to the two file handles, such as in the below example. Attention to the nested “with open” statement.
How to solve the error?
Solution 1: Checking indent of coding
This error often occurs when the coder type a wrong code and cannot indent code correctly, resulting in the system automatically closing the file. Hence, they cannot do any I/O operation on that file. To solve it, you should recheck your indent of the write or read commands to ensure it is inside the with statement.
Another way to avoid this error is to have an if statement to check if the file is closed before we try any I/O operations. For instance:
Solution 2: Handling two files with different names
Remember that in Python, you can redeclare a variable with an already name. This would lead to some of your file handles being possible to have the same names. However, we do not recommend this as it is difficult to manage and use. Instead, you should have a different name for each file handle, such as:
As we have recommended in the first solution, you should have an if statement to make sure the file is opening before approaching it:
Summary
We have learned how to deal with the “ValueError: I/O operation on closed file” error in Python. By checking the indent of the statements and changing names for different file handles as guided in our tutorial, you can easily solve it.
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Python ValueError: I/O operation on closed file Solution
You can only read from and write to a Python file if the file is open. If you try to access or manipulate a file that has been closed, the “ValueError : I/O operation on closed file” appears in your code.
In this guide, we talk about what this error means and why it is raised. We walk through two examples of this error so you can learn how to solve it.
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ValueError : I/O operation on closed file
It has become good practice in Python to close a file as soon as you have finished working with the file. This helps you clean up your code in the Python interpreter. Once a file has been closed in a Python program, you can no longer read from or write to that file directly.
There are two common scenarios where the “ValueError : I/O operation on closed file” is encountered:
- When you forget to indent your code correctly in a “with” statement
- When you try to read a file after it has been closed using the close() statement
Let’s walk through each of these scenarios and discuss them in detail.
Cause #1: Improper Indentation
Let’s write a program that reads a list of student grades from a CSV file. Our CSV file is called students.csv. It currently stores the following data:
To start, we import the csv library in our code so we can read our CSV file. We then use a with statement to open our file:
This code opens the file “students.csv” in read (“r”) mode. We assign the contents of the file to the variable “read_file”.
Let’s print each student’s record to the console:
We use a “for” loop to iterate over every item in the “read_file” variable. This variable stores our CSV file in a list. Next, we use indexing to access each value from each student record. We print each of these values to the console.
Our code returns an error. This is because we’ve tried to iterate over “read_file” outside of our with statement. The “read_file” variable can only read inside the with statement. After the with statement is executed, the file is closed.
To solve this problem, we need to indent our for loop so that it is within our with statement:
Run this revised code:
Our code successfully executes.
Cause #2: Accessing a Closed File
While with statements are the most common way of accessing a file, you can use an open() statement without a with statement to access a file.
Read the contents of our “students.csv” file:
We use the open() method to open the “students.csv” file in read mode. We then use the csv.reader() method to read our CSV file. We then close our file because we have read its contents into a variable.
Next, print each record from our file to the console using a for loop:
This for loop is the same as the one from our last example. The loop prints out all the information about each record in our CSV file. Let’s test out our code:
Our code raises an error. This is because we try to iterate over “read_file” after we have closed our file. To solve this error, we should close our file after we have iterated over “read_file”:
Let’s run our code again:
Our code executes successfully. The values in “read_file” are accessible until we close our file. Because we’ve used our for loop before our close() statement, our code executes without an error. Once we print each student record to the console, we close our file.
Conclusion
The “ValueError : I/O operation on closed file” error is raised when you try to read from or write to a file that has been closed.
If you are using a with statement, check to make sure that your code is properly indented. If you are not using a with statement, make sure that you do not close your file before you read its contents.
Now you’re ready to solve this error like a Python expert!
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