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To clear an existing file before writing new text, open it in write mode: open("example.txt", "w", encoding="utf-8"). Python truncates the file to zero bytes as soon as it opens it. If the file is already open, seek to the beginning and truncate it instead.
Choose the right way to clear the file
| Situation | Use | What it does |
|---|---|---|
| Clear a file before writing text | open(path, "w", encoding="utf-8") |
Truncates the file when opened; creates it if it does not exist, subject to filesystem permissions. |
| Clear a file before writing bytes | open(path, "wb") |
Truncates the file and uses binary I/O, which reads and writes bytes. |
| Clear a file object that is already open | f.seek(0); f.truncate(0) |
Resizes the existing writable stream to zero bytes. |
| Resize a file by path or file descriptor | os.truncate(path, 0) or os.ftruncate(fd, 0) |
Uses an operating-system-level API to set the file length to zero. |
Clear a file by opening it in write mode
Use this when you are starting a new write operation and do not need to preserve the old contents:
with open("example.txt", "w", encoding="utf-8") as f:
f.write("Replacement contentsn")Opening with "w" truncates an existing file immediately—before write() runs. It also creates a missing file when permissions allow. The with statement closes the file when its block ends. See Python’s documentation for open() and file modes.
For text files, specifying encoding="utf-8" avoids relying on the platform-dependent default encoding. For binary data, use "wb" and write bytes, not str. Python’s I/O tutorial explains the distinction between text and binary streams.
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#1 Best Overall
Elebase USB to USB C Adapter for iPhone 18 Pro Max,USBC Car Charger Adapter
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
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Clear a file that is already open
If you need to keep using an existing writable, seekable file object, move its position to the start and truncate there:
with open("example.txt", "r+", encoding="utf-8") as f:
f.seek(0)
f.truncate(0)
f.write("Replacement contentsn")"r+" opens an existing file for reading and writing, but it does not clear the file by itself. The explicit seek(0) and truncate(0) do that. Without a size argument, truncate() cuts the stream at its current position; therefore, seek to zero first if the goal is to empty it. The Python I/O reference documents this behavior and notes that truncation does not change the current position.
Rank #2
Anker USB-C Hub, 5-in-1 USB Hub for Laptops, 4K HDMI Multiport Adapter
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
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Use the operating-system truncation functions when appropriate
Python also provides path- and descriptor-based alternatives in os:
import os
os.truncate("example.txt", 0)For an open file descriptor, use os.ftruncate(fd, 0). These functions set the file length in bytes and are documented for Unix and Windows. See os.truncate() and os.ftruncate(). The Python FAQ also shows an open-file truncation example using rb+ and os.ftruncate: Python FAQ: library.
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Quick Recap
Bestseller No. 5
Best Value
Anker USB C Hub, 5-in-1 USBC to HDMI Splitter with 4K Display
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
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- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
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Sale
UGREEN USB to USB C Adapter Combo 4-Pack, 10Gbps USB C Converter Space Gray
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
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Anker USB C Hub, 7in1 Multi-Port USB Adapter, 4K@60Hz USBC to HDMI Splitter
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
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- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Important details and common mistakes
- Do not use write mode unless deleting the old contents is intended. The truncation takes place at open time, so an error later in the program does not restore the old file.
- Truncation sizes are bytes. This matters for non-ASCII text and binary files. To empty a text file, use the supported beginning-of-file position rather than treating a character count as a byte offset.
- The stream must support the operation. Seeking and truncating require suitable seekable and writable streams; pipes and other non-seekable streams cannot be cleared this way. The I/O reference describes stream capabilities.
- Truncation and disk durability are separate. Buffered file objects can flush pending data with
f.flush(); if the requirement is to request that data be forced to disk, callos.fsync(f.fileno())after flushing.fsync()does not clear the file—it is not a substitute for truncation.
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