i o operation on closed file python что значит
ValueError : I/O operation on closed file
Here, p is a dictionary, w and c both are strings.
When I try to write to the file it reports the error:
5 Answers 5
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 was getting this exception when debugging in PyCharm, given that no breakpoint was being hit. To prevent it, I added a breakpoint just after the with block, and then it stopped happening.
Not the answer you’re looking for? Browse other questions tagged python csv file-io io or ask your own question.
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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.
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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.
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:
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”.
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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:
I have tried with the class below, execute commands in sequence with subporcess module in python2.6.
However, if I try the following code, I get the error: ValueError: I / O operation on closed file
Anyone have idea what can be wrong? I thank
3 Answers 3
The manual says it all really:
After you run the first command and get the result, the ‘bconsole’ process has terminated, the pipes are closed and hence the error on the second communicate call.
Thanks to everyone who somehow tried to help me. As a solution to the problem, I made the following:
I created a method «console» and all other methods of my class I start.
This solved my problem.
Better way is to do as below,
Any sub process initialization must be encapsulated with try catch, to handle resource allocation failures. Then return it, if success.
Before communicating, check whether channel is established (no errors) then communicate.
Best way is to keep «Popen» on the same place whereever you communicate.You may end up duplicating «Popen» two times. But this is safe.
Any unknown interrupts between “Popen” and “communicate”, will make your python job as hanging forever and will need manual kill. This is certainly what we don’t want in live
Before anyone says that this is a duplicate, I do not think it is because I have looked at the similar questions and they have not helped me!
I am creating a Flask server in python, and I need to be able to have a url that shows a pdf.
I tried to use the following code:
However, this does not work because when I run the code I get this error:
How is this the case? My return statement is inside the with statement, therefore shouldn’t the file be open?
I tried to use a normal static_file = open(. ) and used try and finally statements, like this:
The same error happens with the above code, and I have no idea why. Does anyone know what I could be doing wrong?
Sorry if I am being stupid and there is something simple that I made a mistake with!
2 Answers 2
Use send_file with the filename, it’ll open, serve and close it the way you expect.
Despite @iurisilvio’s answer solves this specific problem, is not a useful answer in any other case. I was struggling with this myself.
All the following examples are throwing ValueError: I/O operation on closed file. but why?
I am doing something slightly different. Like this:
In the first two cases, the answer is simple:
Ofcourse in this case, would be stright forward to provide the file name. But in other cases, may be needed to wrap the file stream in some manipulation pipeline (decode / zip)
ValueError: I/O operation on closed file
Помогите пожалуйста получить выходные значения, я новичок и код работает с ошибкой
Вложения
 | sentences.txt (2.8 Кб, 10 просмотров) |
Ошибка cannot perform this operation on a closed dataset
Доброго времени! Релизовывал алгоритм удаления пользователя из бд, почему-то пишет, что датасет.
ADOQuery4: Cannot perform this operation on a closed dataset
Здравствуйте. Н Д закрыт, как можно исправить проблему, затык на showmessage(‘3тап 4’); датасет.
Catstail, Задача 1: сравнение предложений
Дан набор предложений, скопированных с Википедии. Каждое из них имеет «кошачью тему» в одном из трех смыслов:
кошки (животные)
UNIX-утилита cat для вывода содержимого файлов
версии операционной системы OS X, названные в честь семейства кошачьих
Ваша задача — найти два предложения, которые ближе всего по смыслу к расположенному в самой первой строке. В качестве меры близости по смыслу мы будем использовать косинусное расстояние.
sentences.txt
Выполните следующие шаги:
Добавлено через 2 минуты
Выходит ошибка на 21 строке
ValueError: I/O operation on closed file.