在python进程之间传递二进制数据

Question

I need to transfer binary data between python processes on linux efficiently. However I can't find a way to pass it with pipe. The closest I got was to pass it as string but it keeps its binary form for some reason so it causes me problems.

ciphertext, tag = cipher1.encrypt_and_digest(input().encode())
print(ciphertext)

ciphertext is binary but when I test its type at the other process

print(type(sys.stdin.read()))

I get

<class 'str'>

Any ideas?

Answer 1

In Python 3 you can't use print or input for binary data. They're designed for handling text (Unicode), not binary. You can use file .write and .read calls to sys.stdout.buffer and sys.stdin.buffer , which are the underlying binary buffers to stdin and stdout. You can't use sys.stdout and sys.stdin since they're for text. There's a brief Note about this at the end of the docs for sys.stdin and sys.stdout .

Here's a short demo.

In "send_bytes.py" we create a bytes string data that contains all the possible byte values and write it to sys.stdout.buffer . We pipe that output to "get_bytes.py" where we read it and check to make sure it has all the right bytes in the right places.

send_bytes.py

#! /usr/bin/env python3

''' Write some binary data to stdout '''

import sys

# Make a bytes string containing all possible byte values
data = bytes(range(256))

#Send it as binary to stdout
out = sys.stdout.buffer
out.write(data)

get_bytes.py

#! /usr/bin/env python3

''' Read some binary data from stdin '''

import sys

#Read binary data from stdin
infile = sys.stdin.buffer
newdata = infile.read()

print(newdata)

# Make a bytes string containing all possible byte values
data = bytes(range(256))

#Check that the read data is correct
print(newdata == data)    

We run the programs using this command line:

$ python3 ./send_bytes0.py | python3 ./get_bytes0.py   

Here's the output printed by "get_bytes0.py"

b'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff'
True