Converting list of numbers to binary file

Question

I have a very long list of large numbers in Python in the form

[429996711.2753906, 106845465.30664062, 47285925.673828125, 373352395.4082031, 934463030.1191406, 53994183.962890625, 455503649.6542969, 741004174.1660156, 725379998.9648438, 485329924.8046875, 16476769.255859375,...]

for example. I need to convert each number from decimal to binary, and then save these binary numbers into a raw binary file without CRLF line-endings. Would anyone be able to say how to do this? I haven't been able to find a usable answer anywhere. Thanks!

You might want to take a look at the struct package: https://docs.python.org/3/library/struct.html. — daniel kullmann, Apr 02 '20 at 22:49

score 1 · Answer 1 · answered Apr 02 '20 at 22:55

Convert your decimals to a bytearray or similar - see this SO thread on converting floats to bytearray
Write the bytearray to a file in binary mode - use the "wb" mode in an open() function to mark the file as binary, as discussed in this SO thread on how to write a bytearray of ints to a binary file.

# make file
newFile = open("filename.txt", "wb")
# write to file
newFile.write(myBytearray)

score 1 · Accepted Answer · answered Apr 02 '20 at 22:56

This snippet creates a file data.bin with 88 bytes (11 doubles of 8 bytes each):

import struct

data = [429996711.2753906, 106845465.30664062,
    47285925.673828125, 373352395.4082031,
    934463030.1191406, 53994183.962890625,
    455503649.6542969, 741004174.1660156,
    725379998.9648438, 485329924.8046875,
    16476769.255859375]

packed = map(lambda i: struct.pack("@d", i), data)

with open("data.bin", "wb") as fh:
    for i in packed:
        fh.write(i)

Converting list of numbers to binary file

2 Answers2