Sending a string to a program

Question

I am trying to send a string from a program 1 to another program program 2, both in python 3
e.g.

#_____________________________________1.py
a = input('Type in a string: ')
#                                     send somehow a string a from this program
#                                     to the second program

I want to somehow send a string a to my second program so it will print out a:

#_____________________________________2.py
#                                     receive somehow a string from the first
#                                     program and store it in a
print(a)

How do I do this?

I am still a beginner programmer and would love it if you could help me.

1. I need to be able to enter the string in 1.py
2. I need then be able to access the string that I entered from 2.py.
3. I have to have them as two separate files.

---

ANSWER:

I found a way to solve this.

import subprocess
username = input()
subprocess.Popen(['python.exe', 'file.py', username])

Answer 1

There are multiple ways to do that, you could use socket, file, pipe, shared-memory, message, ... to transfer a string from one process to another.

As an example of using messages, ZeroMQ provides an easy messaging library to do that smarter, than with system (raw, low level) sockets:
for more details look into http://zguide.zeromq.org/

A HelloWorld server example:

import time
import zmq

context = zmq.Context()
socket = context.socket(zmq.REP)
socket.bind("tcp://*:5555")

while True:
    #  Wait for next request from client
    message = socket.recv()
    print("Received request: %s" % message)

    #  Do some 'work'
    time.sleep(1)

    #  Send reply back to client
    socket.send(b"World")

A HelloWorld client example:

import zmq

context = zmq.Context()

#  Socket to talk to server
print("Connecting to hello world server…")
socket = context.socket(zmq.REQ)
socket.connect("tcp://localhost:5555")

#  Do 10 requests, waiting each time for a response
for request in range(10):
    print("Sending request %s …" % request)
    socket.send(b"Hello")

    #  Get the reply.
    message = socket.recv()
    print("Received reply %s [ %s ]" % (request, message))

With files, you write a file with program A then poll on it with program B.

Answer 2

You have many way communicate between two or N python program, Ex:

• Socket
• Database - MySQL, Mongodb, SQL Server... etc

or maybe you can try ZeroMQ

Answer 3

# file_1.py
def get_input():
    return input('Type in a string: ')

# file_2.py
from file_1 import get_input

print(get_input())

Answer 4

Most common way of two programs communicating together is through http, tcp or other protocol. The same way as your browser (one program) communicates with the web server (another program).

You can send http request from one program and the second has to listen for that.

If you want more info, look for SOA. It is a bit more complicated than that, so if you have any questions, ask.

Answer 5

I found the answer.

import subprocess
username = input()
subprocess.Popen(['python.exe', 'file.py', username], subprocess.creationflags=CREATE_NEW_CONSOLE)