What does open() return in Python?

Michael 138 Published: 09/03/2024

What does open() return in Python?

I'm happy to respond in English this time!

In Python, the open() function is used to open a file and return a file object, which can be read from or written to. The syntax for opening a file using open() is as follows:

file_object = open(file_name, mode)

Where:

file_object: This is a variable that will hold the file object returned by the open() function.

file_name: This is the name of the file you want to open. It can be a string or a bytes-like object (like b'test.txt' for a binary file). mode: This is an optional parameter that specifies how you want to interact with the file. The mode can be: 'r': Open the file for reading only. 'w': Open the file for writing only, truncating any existing content. 'a': Open the file for appending (writing to the end of the file), without truncating any existing content.

'x': Open the file for exclusive creation (create a new file if it doesn't exist; fail if it does). 'b': Open the file in binary mode (for files containing non-text data). 't': Open the file in text mode (default; use this unless you're working with binary data).

The open() function returns a file object that provides methods for reading (read(), readline(), etc.) and writing (write(), writelines(), etc.) to the file. You can also perform various operations on the file, such as seeking (seek()), telling where you are in the file (tell()), and checking if the end of the file has been reached (eof).

Here's an example:

with open('test.txt', 'w') as f:

f.write('Hello, world!')

In this example, we're opening a file named test.txt in write mode ('w') and creating a file object f. We then use the write() method to write the string 'Hello, world!' to the file. Finally, we close the file using the with statement.

So, to summarize: open() returns a file object that you can read from or write to, depending on how you specify the mode when opening the file.

What is the return value of open in python for loop

I'm happy to respond in English!

The open() function in Python returns a file object, which represents the opened file. The file object is an instance of the file class and provides methods for reading and writing data.

In a for loop, if you open a file multiple times, it will return the same file object each time. This is because the file object is stored in memory and remains valid until the program closes the file or ends.

Here's an example:

for i in range(3):

with open('example.txt', 'r') as f:


print(f.read())

In this example, the open() function is called three times in the for loop, but it will return the same file object each time. The with statement ensures that the file is properly closed after reading.

When you call open() multiple times, Python does not create a new file object each time. Instead, it reuses the existing file object. This is an optimization to reduce memory usage and improve performance.

Here's what happens under the hood:

The first time open() is called, it creates a new file object and returns it. The second time open() is called, Python checks if there is already an open file object with the same name. If there is, it reuses the existing file object and returns it. Subsequent calls to open() will also reuse the existing file object.

This behavior applies not only to for loops but also to any block of code where open() is called multiple times.

Keep in mind that if you want to open a different file each time, you need to use a unique filename or path. For example:

for i in range(3):

with open(f'example_{i}.txt', 'r') as f:


print(f.read())

In this case, Python will create a new file object each time open() is called because the filenames are different.

In summary, when you call open() multiple times in a for loop, it will return the same file object each time. This optimization improves performance and reduces memory usage.

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