When working with large files in Python, it may be necessary only to read the last line of the file rather than reading the entire file into memory. This can be an efficient and memory-saving solution, especially when working with large files that may exceed the available memory on your machine. In this article, we will explore various methods for reading the last line of a file in Python.

Method 1: Using readlines()

The first method for reading the last line of a file in Python is to use the readlines() method. The readlines() method returns a list of all the lines in the file, so we can access the last element of the list to retrieve the last line of the file.

				
					with open("file.txt", "r") as file:
    lines = file.readlines()
    last_line = lines[-1]

This method is straightforward to understand but has a significant drawback. Since readlines() load all the file’s lines into memory, it can be slow and memory-intensive when working with large files.

Method 2: Using seek() and tell()

Another method for reading the last line of a file in Python is to use the seek() and tell() methods. The seek() method allows us to move the file pointer to a specific position in the file, while the tell() method returns the current status of the file pointer.

				
					with open("file.txt", "r") as file:
    file.seek(0, 2)
    file_size = file.tell()
    file.seek(max(0, file_size - 1024), 0)
    last_line = file.readlines()[-1]

In this example, we first move the file pointer to the end of the file using seek(0, 2). Then we retrieve the size of the file using tell(). Finally, we move the file pointer to a position of 1024 bytes from the end of the file using seek(max(0, file_size - 1024), 0) and read the last line using readlines(). This method is more efficient than the readlines() method, as it only reads a portion of the file into memory.

Method 3: Using tail command

The third method for reading the last line of a file in Python is to use the tail command. The tail command can be used to display the last N lines of a file, and it can be easily integrated into a Python script using the subprocess module.

				
					import subprocess

last_line = subprocess.run(["tail", "-1", "file.txt"], stdout=subprocess.PIPE).stdout.decode("utf-8")

In this article, we have explored three methods for reading the last line of a file in Python: using readlines(), using seek() and tell(), and using the tail command. While each method has its own strengths and weaknesses, the most efficient method will depend on the size of the file and the

Wrap up

We have explored three methods for reading the last line of a file in Python: using readlines(), using seek() and tell(), and using the tail command. While each method has its strengths and weaknesses, the most efficient way will depend on the size of the file and the amount of available memory. The readlines() method may be sufficient when working with small files. The seek() and tell() method or the tail command may be more appropriate for larger files.

Choosing the most efficient method for your specific use case is important, as reading large files into memory can quickly become a bottleneck in your program. When working with large files, it is also essential to be mindful of memory usage and choose an efficient and memory-saving method.

Overall, Python provides several options for reading the last line of a file, and it is up to the programmer to choose the most appropriate method or for their specific use case. However, regardless of the method selected, Python provides a versatile and powerful platform for working with files and data.


Thanks for reading. Happy coding!