Read / write binary file with bytes Dry Run in PYTHON

Read / write binary file with bytes is an interactive PYTHON dry run visualizer from the Bytes programs section. Study the source code, then use the execution controls to follow each step, variable update, highlighted line, and console output.

This page provides a browser-based dry run with source-code highlighting, auto-scroll, voice narration controls, and execution output for learning the program step by step.

Read / write binary file with bytes Program Code

# write bytes to binary file
data = b"Hello, binary world!\x0aSecond line."
with open("sample.bin", "wb") as f:
    f.write(data)

# read bytes from file
with open("sample.bin", "rb") as f:
    read_data = f.read()

print("written:", data)
print("read:   ", read_data)
print("equal?  ", data == read_data)

# modify with bytearray (in-memory)
ba = bytearray(read_data)
ba[0:5] = b"HELLO"   # replace "Hello" → "HELLO"
with open("sample_modified.bin", "wb") as f:
    f.write(ba)
print("modified written.")

View the complete Bytes programs page.