python subprocess stdin truncated at first space

I have an issue with pOpen.communicate() where the string I send to the subprocess truncates at the first occurrence of a space character I am sending to STDIN (keep in mind I am encoding to bytes using encoding utf-8)

Input file text.txt

this is an input string

My code

from subprocess import Popen, PIPE
# open file and encode to utf-8 bytes
fp = open('test.txt')
inputs = fp.read()
inputBytes = bytes(inputs, 'utf-8')
# open subprogram and send the bytes to STDIN
p = Popen(['./program'], stdout=PIPE, stdin=PIPE, stderr=PIPE)
stdout_data = p.communicate(input=inputBytes)
# print STDOUT of subprocess, will print what was given
out = str(stdout_data).split('\\n')
for frame in out:
    print(frame)

my expected output:

(b'this is an input string', b'')

what I got:

(b'this', b'')

am I using the wrong encoding format? The subprogram is a go application that uses scanf to listen to pOpen.communicate() data

package main
import "fmt"
func main() {
	var inputs string
	fmt.Print("")
	fmt.Scanf("%s", &inputs)
	fmt.Println(inputs)
}

Go's fmt.Scanf is based on C's scanf; %s skips leading spaces and then reads the next word up to the first space. That's probably not what you wanted.

From the docs, a bit more precise:

> Input processed by verbs is implicitly space-delimited: the implementation of every verb except %c starts by discarding leading spaces from the remaining input, and the %s verb (and %v reading into a string) stops consuming input at the first space or newline character. (https://pkg.go.dev/fmt)