CODE EXAMPLE FOR PYTHON

file handling in python append byte

file = open('myfile.dat', 'wb')
file.write('This is a sample')
file.close()

file = open('myfile.dat', 'ab')
file.seek(5)
file.write(' text')
file.close()

file = open('myfile.dat', 'rb')
print file.read()  # -> This is a sample text