p = subprocess.Popen("/home/pj/Desktop/L1/lab1",stdin=subprocess.PIPE, stdout=subprocess.PIPE)
print (p.communicate()[0])

b'Please supply the code: nIncorrectn'

In [10]: p=subprocess.Popen(("bash", "-c","echo -n 'prompt:'; read -r data; echo $data"),stdin=subprocess.PIPE,stdout=subprocess.PIPE)

In [11]: p.communicate('foobar')
Out[11]: ('prompt: foobarn', None)

In [1]: import pexpect.fdpexpect

In [8]: p=subprocess.Popen(("bash", "-c","echo -n 'prom'; sleep 5; echo 'pt: '; read -r data; echo $data"),stdin=subprocess.PIPE,stdout=subprocess.PIPE)

In [10]: o=pexpect.fdpexpect.fdspawn(p.stdout.fileno())

In [12]: o.expect("prompt: ")
Out[12]: 0

In [16]: p.stdin.write("foobar")    #you can communicate() here, it does the same as
                                    # these 3 steps plus protects from deadlock
In [17]: p.stdin.close()
In [18]: p.stdout.read()
Out[18]: 'foobarn'