Don’t know how to determine the end of file in Python? Do not worry; we got you covered. This tutorial explains various Python methods for determining whether a file has reached its end of file.

End Of File, or EOF, is the final point the program reaches when users can no longer read the file’s data. In other words, the program has read the entire file through to the finish.

Additionally, you will get empty strings as outputs once the EOF is reached. Users must therefore be aware of a file’s end of file status. This will help you prevent errors caused by trying to read input from a file after it has ended.

Method 1: Determine End Of File In Python Utilizing file.read()

File.read() is a Python pre-built function that can be utilized to read a file’s contents. Suppose the result of the approach file.read() is one empty string; the end of file (EOF) has been reached.

You can see in the example below:

with open("example-file.txt", "r") as f:
    while True:
        file_eof = file_open.read()
        if file_eof == '':
            print('The end of the file')
            break

Notice that the mode “r” is utilized to read your file only when calling the function open() to open this file at the beginning of a program. In order to verify that the output returned at the end is empty, utilize the conditional statement if.

Method 2: Determine End Of File In Python Utilizing The Approach readline() With The Loop While

The approach readline() is also a pre-built function in Python that can read the entire line of the text files. The loop while in Python repeatedly checks the specified condition in the code block until it is true. When it is unknown in advance how many iterations will occur, this loop is employed.

With the method readline() and the loop while, you can repeatedly read the lines from the provided text file.

Here is an example for your reference.

example_file = 'example-file.txt'
example_text = open(example_file, "r")
x = True

while x:
    file_line = example_text.readline()
    if not file_line:
        print("The end of the file")
        x = False

example_text.close()

Output:

The end of the file

Notice that the loop while will cease iterating once there is no longer any text in text files for readline() to read.

Method 3: Determine End Of File In Python Utilizing Walrus Operator

Python 3.8 adds the new Walrus operator, which is indicated by the symbol :=. In essence, Walrus is an assignment operator that assigns the values True and prints them right away.

Check out the example below for a better understanding.

ex_file = open("example-file.txt", "r")
while (f := ex_file.read()):
    process(f)
ex_file.close()

In this case, characters that will be read by the function read() from a text file are represented by the values True. This indicates that it will cease once the file document is finished printing.

The Bottom Line

So there you have several methods that can help you determine the end of file in Python. You can try out all three approaches provided in this guide and pick the one that best suits your needs.

Hopefully, you find this tutorial useful and easy to follow. Suppose you want to learn more Python skills; check out our other guides, such as how to overwrite files or create requirements.txt files in Python.