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Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Use Python’s built-in open() function to read or write a file, and wrap it in a with block so the file closes reliably. Choose a mode that matches your intent: r reads, w replaces existing contents, a appends, and x creates a new file only. For text, specify the known encoding—commonly "utf-8"—rather than relying on a machine’s default.
Read a text file with open()
open(path, mode, encoding=...) returns a file object. If you omit the mode, Python opens the file for text reading, equivalent to "r". This example makes both the mode and encoding explicit:
with open("notes.txt", "r", encoding="utf-8") as file:
contents = file.read()
print(contents)The with block closes the file when the block ends, including if an exception interrupts the work. Python’s official tutorial recommends using with for file objects; it avoids having to close the file manually.
Read one line at a time
For a file that may be large, iterate over it instead of loading all its contents into one string:
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with open("notes.txt", encoding="utf-8") as file:
for line in file:
print(line, end="")Iteration processes each line as it is read. The end="" argument prevents print() from adding an extra line break when the line already ends with one.
Choose a file mode that matches the task
| Mode | Purpose | What happens to existing contents? |
|---|---|---|
r |
Read a file. This is the default mode. | Unchanged. |
w |
Write from the start. | Truncated: existing contents are erased when the file is opened for writing. |
a |
Append new content. | Kept; writing begins at the end. |
x |
Create a new file exclusively. | Opening fails if a file with that name already exists. |
+ |
Allow both reading and writing when combined with another mode. | Depends on the mode it is combined with. |
Use t to indicate text mode and b for binary mode. Text mode is the default, so "r" and "rt" both mean text reading. Combine the letters when needed, such as "rb" for reading bytes.
Write a file without accidentally losing data
Warning: opening a file with "w" truncates it, erasing any previous contents. Use it only when replacement is intended:
with open("notes.txt", "w", encoding="utf-8") as file:
file.write("First linen")To add text without replacing what is already there, use "a":
with open("notes.txt", "a", encoding="utf-8") as file:
file.write("Another linen")Choose "x" when the file must be new and an existing file should not be overwritten:
with open("new-notes.txt", "x", encoding="utf-8") as file:
file.write("Created oncen")Text mode and binary mode are for different data
| Mode | Data exposed to your code | Transformations | Typical use |
|---|---|---|---|
| Text | str |
Encodes strings on writing, decodes bytes on reading, and may translate line endings. | Text files, such as notes or configuration files. |
| Binary | bytes |
No text encoding or decoding and no newline translation. | Images, executables, and byte-level processing. |
For example, read an image in binary mode:
with open("photo.jpg", "rb") as file:
image_data = file.read()Do not pass encoding= in binary mode. Text newline conversion is useful for ordinary text but can alter data that must remain byte-for-byte intact.
Specify the encoding for text files
A text file’s encoding is a choice made by the file’s format or the program that created it; not every text file is UTF-8. When you know a file is UTF-8, state that explicitly:
with open("data.txt", encoding="utf-8") as file:
text = file.read()If you omit encoding, the default text encoding depends on the platform or locale, so code can behave differently across environments. The Python io documentation recommends specifying the encoding explicitly where appropriate. Python 3.10 and later also support encoding="locale" when using the current locale encoding is intentional; for a known UTF-8 file, use "utf-8" instead.
Use pathlib for path-oriented file work
pathlib.Path makes it convenient to compose paths and provides methods for common file operations. For example, join a directory and filename with /, then read UTF-8 text:
from pathlib import Path
path = Path("data") / "notes.txt"
text = path.read_text(encoding="utf-8")Path.open() works like the built-in open(). The whole-file convenience methods read_text() and read_bytes() return text and bytes respectively. Their write counterparts, write_text() and write_bytes(), open, write, and close the file—and overwrite an existing file—so take the same care as with "w".
Use open() when you want explicit mode control, line-by-line iteration, or a file object for a longer operation. Use pathlib when path composition or concise whole-file operations make the code clearer.
Quick Recap
Official Python documentation
- Python Tutorial: Input and Output—file modes, reading and writing, and using
with. - Python built-in
open()reference—arguments, modes, and defaults. - Python
ioreference—text and binary streams and encoding guidance. - Python
pathlibreference—path objects and file methods.
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