For a general text file, read it line by line and keep the most recently read line. This uses memory for only one line at a time, even though Python still reads the file from start to finish.
Read the last line without storing the whole file
Python file objects can be iterated one line at a time. Use a None sentinel so an empty file is distinguishable from a file whose final line is blank:
As an Amazon Associate I earn from qualifying purchases.
last_line = None
with open(path, encoding="utf-8") as f:
for line in f:
last_line = line
if last_line is not None:
last_line = last_line.rstrip("rn")Replace path with the file path and use the file’s actual encoding if it is not UTF-8. Specifying an encoding avoids relying on a platform-dependent default. The with block closes the file when it exits, including if an exception occurs. Python’s tutorial on input and output describes iterating over a file and its line-reading behavior; the built-in open() reference documents encoding and newline options.
Keep or remove the line ending
Iteration normally returns the line terminator along with the line. The final line may have no terminator if the file does not end with a newline. The rstrip("rn") call removes trailing carriage-return and newline characters, but leaves other whitespace intact. Omit it if the caller needs the line ending.
#1 Best Overall
With default universal-newline handling, Python translates common input line endings such as CRLF and CR to n. If the original line-ending bytes matter, read in binary mode or configure newline handling deliberately, then decode with an approach appropriate to the file format.
Handle empty files and blank final lines
If the file is empty, the loop does not run and last_line remains None. A blank final line is still a line: before trimming, its value is a newline string. Checking last_line is not None preserves that distinction; checking only whether the value is truthy after stripping could lose it. Python’s file input tutorial also explains that readline() returns an empty string at end-of-file, unlike a blank line, which contains a line terminator.
Choose an approach for your file
| Approach | When it fits | Tradeoff |
|---|---|---|
| Iterate and retain the last line | General text files; the recommended default | Reads the file sequentially, but does not keep all its lines in memory. |
readlines(), then select the final item |
Small files where retaining all lines is acceptable | Creates a list containing the file’s lines, so memory use grows with the file. |
| Scan backward from the end | Specialized large-file optimization when the encoding and file format are known | Requires careful binary handling of encoding and line boundaries; arbitrary end-relative offsets are not generally valid text-stream positions. |
Use readlines() for small files
with open(path, encoding="utf-8") as f:
lines = f.readlines()
last_line = lines[-1] if lines else NoneThis is compact and straightforward, but readlines() stores all lines in a list. Python documents this list-producing behavior in its file input tutorial and I/O reference.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Why not seek backward in a text file?
A tempting shortcut is to seek a fixed number of bytes backward from the end, then read forward. That is not a safe general recipe for a text stream: Python restricts text-mode seeking to supported positions, and arbitrary offsets from the end are not generally valid. Even in binary mode, a correct reverse scan must account for the encoding, possible multibyte characters, CRLF boundaries, empty files and trailing newline runs. See the Python tutorial and I/O reference for text-stream seek semantics.
For ordinary text files, iteration is the simpler choice. A backward scan is appropriate only when its binary and encoding assumptions are explicit and the extra complexity is justified.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
