os.sendfile(dest, source, offset, count) 

# Python program to explain os.sendfile() method 
  
# importing os module 
import os
  
  
# Source file path
source = './Python_intro.txt'
  
# destination file path
dest = './newfile.txt'
  
# Open both files and get
# the file descriptor
# using os.open() method
src_fd = os.open(source, os.O_RDONLY)
dest_fd = os.open(dest, os.O_RDWR | os.O_CREAT)
  
# Now send n bytes from
# source file descriptor
# to destination file descriptor
# using os.sendfile() method
offset = 0
count = 100
bytesSent = os.sendfile(dest_fd, src_fd, offset, count)
print("% d bytes sent / copied successfully." % bytesSent)
  
# Now read the sent / copied
# content from destination
# file descriptor 
os.lseek(dest_fd, 0, 0)
str = os.read(dest_fd, bytesSent)
  
# Print read bytes
print(str)
  
# Close the file descriptors
os.close(src_fd)
os.close(dest_fd)

100 bytes sent/copied successfully.
b'Python is a widely used general-purpose, high level programming language.
It was initially designed '