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# Write (content must be bytes)
sandbox.write_file("/tmp/hello.txt", b"Hello!").result()

# Read (returns bytes)
content = sandbox.read_file("/tmp/hello.txt").result()
print(content.decode())
Like exec(), file operations return an OperationRef immediately and don’t wait for completion. Call .result() when you need the data. This lets you start multiple operations and wait for them together: 
refs = [sandbox.write_file(f"/tmp/{i}.txt", b"data") for i in range(5)]
for ref in refs:
    ref.result()
For parallel upload and download patterns and S3 mounts, see the File operations guide.
Last modified on May 29, 2026