How to close all the opened files using Python?

In Python, file-handling tasks like opening, reading, writing, and closing files, or manipulating data in files are a common occurrence. While opening files has its significance and utility, it's equally important that files are closed properly to release system resources and to ensure that data integrity is maintained. In this article, we will explore different methods and techniques to close multiple opened files in Python, permitting you to optimize your file-handling operations and maintain clean code.

Making Use of a Context Manager

In Python, context managers are a tool for efficiently managing resources that need to be properly initialized and cleaned up. They are commonly used along with the 'with statement'. They automatically oversee setup and teardown operations, ensuring that resources are promptly released even if exceptions are encountered. They see to it that files are automatically closed when they go out of scope, even when exceptions occur.

Context managers deliver cleaner, more readable, and error-free code when working with resources that require careful management. Python has provision for built-in context managers and even permits us to create custom ones.

Example

Here, in this example, the open() function is used with the 'with statement' to open two files, namely, file1.txt in read mode and file2.txt in write mode. These files are assigned to two variables file1 and file2. We are allowed to perform any desired operations on the opened files within the 'with block'. Once the 'with block' is exited, the context manager automatically ensures that the files are closed, regardless of whether an exception has occurred or not.

with open('file1.txt', 'r') as file1, open('file2.txt', 'w') as file2:
   # Perform operations on the opened files
   # ...

# The files are automatically closed outside the 'with' block

Closing Multiple Files Manually

If there is a collection of file objects that you want to close explicitly, you can do so by manually iterating over them and closing each file separately.

Example

In the code given below, file1.txt is opened in read mode and file2.txt is opened in write mode. After performing the desired operations on the files, you can explicitly close them using the close() method. It's crucial to ensure that you close all the opened files to prevent resource leaks and possible data corruption.

file1 = open('file1.txt', 'r')
file2 = open('file2.txt', 'w')

# Perform operations on the opened files
# ...

# Close the files
file1.close()
file2.close()

Making Use of a List of File Objects

If there is a list of file objects that need to be closed, you can iterate over the list and close each file one by one.

Example

In this example, we make a list of files containing three opened files, namely, file1.txt, file2.txt, and file3.txt. After the required operations are carried out on the files, we iterate over the list making use of a 'for loop', and close each file using the close() method.

files = [open('file1.txt', 'r'), open('file2.txt', 'w'), open('file3.txt', 
'a')]

# Perform operations on the opened files
# ...
# Close all the files
for file in files:
   file.close()

Making Use of a try-finally Block

You can also utilize a try-finally block to make sure that even if an exception occurs when file operations are underway, the files are still closed properly.

Example

In the code given below, the file1.txt is opened in read mode and the file2.txt is opened in write mode. Within the try block, you can carry out any desired operations on the files. The 'finally block' is executed regardless of whether an exception occurred or not. This makes sure that the files are closed properly using the close() method, in spite of an exception being raised during the file operations.

file1 = open('file1.txt', 'r')
file2 = open('file2.txt', 'w')
try:
    # Perform operations on the opened files
    # ...
finally:
    # Close the files
    file1.close()
    file2.close()

Making Use of a Contextlib.closing Wrapper

The contextlib.closing function can be utilized as a context manager to wrap file objects and ensure their proper closure.

Example

Here, in this snippet below, the contextlib.closing function is used to wrap the open() function calls for file1.txt and file2.txt. This makes it possible for us to use the resulting file objects as context managers within the 'with statement'. Similar to previous examples, we can perform operations on the files within the 'with block', and the context manager sees to it that the files are closed properly when the block is exited.

import contextlib
with contextlib.closing(open('file1.txt', 'r')) as file1, 
contextlib.closing(open('file2.txt', 'w')) as file2:
    # Perform operations on the opened files
    # ...

# The files are automatically closed outside the 'with' block

It's important that opened files are closed in Python to release system resources and ensure file handling is proper and efficient. In this article, we navigated through various methods to close multiple opened files. We gained knowledge about using context managers with the 'with statement', which programmatically handles the closing of files when they go out of scope. We also discussed closing files manually using the close() method and showcased how to close a collection of file objects. We also learned about using a 'try-finally block', and the contextlib.closing function.

By implementing these practices and techniques, you can efficiently manage your file-handling operations, keep clean code, and stop resource leaks. It is advisable to always close your files to encourage productive and effective programming habits and avoid potential undesirable issues.