CODEWITHSUNDEEP
pythonpython-3.x
Ivan Baldin
Ivan Baldin

Reputation: 3459

How to write binary data to stdout in python 3?

In python 2.x I could do this:

import sys, array
a = array.array('B', range(100))
a.tofile(sys.stdout)

Now however, I get a TypeError: can't write bytes to text stream. Is there some secret encoding that I should use?

Upvotes: 168

Views: 90760

Answers (4)

Yajo
Yajo

Reputation: 6418

An idiomatic way of doing so, which is only available for Python 3, is:

with os.fdopen(sys.stdout.fileno(), "wb", closefd=False) as stdout:
    stdout.write(b"my bytes object")
    stdout.flush()

The good part is that it uses the normal file object interface, which everybody is used to in Python.

Notice that I'm setting closefd=False to avoid closing sys.stdout when exiting the with block. Otherwise, your program wouldn't be able to print to stdout anymore. However, for other kind of file descriptors, you may want to skip that part.

Upvotes: 25

Marco smdm
Marco smdm

Reputation: 1045

In case you would like to specify an encoding in python3 you can still use the bytes command like below:

import os
os.write(1,bytes('Your string to Stdout','UTF-8'))

where 1 is the corresponding usual number for stdout --> sys.stdout.fileno()

Otherwise if you don't care of the encoding just use:

import sys
sys.stdout.write("Your string to Stdout\n")

If you want to use the os.write without the encoding, then try to use the below:

import os
os.write(1,b"Your string to Stdout\n")

Upvotes: 3

Benjamin Peterson
Benjamin Peterson

Reputation: 20520

A better way:

import sys
sys.stdout.buffer.write(b"some binary data")

Upvotes: 276

Alex Martelli
Alex Martelli

Reputation: 881695

import os
os.write(1, a.tostring())

or, os.write(sys.stdout.fileno(), …) if that's more readable than 1 for you.

Upvotes: 19

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