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Write Binary File

Zero-dependency Python snippets for writing binary files using the standard library.

4 snippets available in this sub-category.

Simple

Write binary file

file write binary bytes open

Write bytes to a binary file

with open("file.bin", "wb") as f:
    f.write(b"Hello, World!")

Notes

  • Use 'wb' mode for binary writing
  • Overwrites existing file
  • Writes bytes object directly

Write binary file from string

file write binary encode string

Write string as binary data with encoding

text = "Hello, World!"
with open("file.bin", "wb") as f:
    f.write(text.encode("utf-8"))

Notes

  • Encodes string to bytes before writing
  • UTF-8 is the most common encoding
  • Handles international characters

Complex

Write binary file with structured data

file write binary struct structured data-types

Write structured binary data with headers and type information

import struct


def write_binary_structure(filename, data_type, data):
    """Write structured binary data to file."""
    with open(filename, "wb") as f:
        if data_type == "string":
            data_bytes = data.encode("utf-8")
            length = len(data_bytes)
            # Write header: length (4 bytes) + type (4 bytes)
            f.write(struct.pack(">II", length, 1))
            f.write(data_bytes)
        elif data_type == "integer":
            f.write(struct.pack(">II", 4, 2))  # length=4, type=2
            f.write(struct.pack(">I", data))
        elif data_type == "float":
            f.write(struct.pack(">II", 4, 3))  # length=4, type=3
            f.write(struct.pack(">f", data))


# Write different data types
write_binary_structure("data.bin", "string", "Hello, World!")
write_binary_structure("data.bin", "integer", 42)
write_binary_structure("data.bin", "float", 3.14)

Notes

  • Uses struct module for binary packing
  • Includes length and type headers
  • Supports multiple data types
  • Useful for custom binary formats

Write binary file with checksum

file write binary checksum md5 struct

Write binary file with checksum for integrity

import hashlib
import struct


def write_binary_with_checksum(filename, data):
    """Write binary data to file with checksum for integrity."""
    checksum = hashlib.md5(data).hexdigest()
    with open(filename, "wb") as f:
        # Write checksum length and checksum
        checksum_bytes = checksum.encode("utf-8")
        f.write(struct.pack(">I", len(checksum_bytes)))
        f.write(checksum_bytes)
        # Write data length and data
        f.write(struct.pack(">I", len(data)))
        f.write(data)

write_binary_with_checksum("data_with_checksum.bin", b"important binary data")

Notes

  • Stores checksum and data length for verification
  • Useful for data integrity and validation
  • Uses struct for binary packing

🔗 Cross-References

🏷️ Tags

file, binary, write, bytes, io

📝 Notes

  • Use open() with mode 'wb' to write binary files
  • Overwrites existing content by default
  • Useful for images, executables, and non-text data