file.truncate() Truncate file
Last updated: 2026-09-22
file.truncate() Truncate file
file.truncate(size=None) resizes the file to size; defaults to the current position.
| Category | File Methods |
|---|---|
| Kind | Built-in Type Method |
| Python Version | all |
📝 Syntax
file.truncate()⚙️ Parameters
| size Optional | Target size after truncation; None means the current position.（Default：None） |
|---|
Returns：int. The file size after truncation.
Mutates the original：No (returns a new object)
💥 Raises
OSError— Raised when the file is not writable or does not support truncation.
▶ Example
Edit the code, press Run, and see the result in the output panel:
Output：
0123💡 Related Cases
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❓ FAQ
QWhat does truncate() do?
AIt truncates the file to a specified size (size bytes). If size is omitted, it truncates at the current position.
QCan I truncate a file opened with 'r'?
ANo; it raises OSError (the file was not opened for writing). You need a writable mode such as 'w', 'a', or 'r+'.
QWhat happens when size is smaller or larger than the current file?
AA smaller size removes the excess content; a larger size makes the file longer (padded with zeros).
QWhat does it return?
AThe file size after truncation.
