In Python, as in many systems, it is easiest to exchange data between programs via files using a format such as JSON.

In many program examples, input is assumed to come from the keyboard and output to the screen.

Using pipes, input can come from the standard input (as a file) and output to the standard output (as a file).

In non-example usage, input comes from many sources (files) and output can go to many targets (files). This is often required when there are more than one input channel and/or more than one output channel.

In the following example, input is in JSON format. Although the program might indicate that input is to be entered, in practice, input would be piped in via the standard input and piped out to the standard output.

Here is the Python code [#1]
import sys import json print("Enter a list in JSON format.") text1 = sys.stdin.read() print("You entered \"{0:s}\".".format(text1)) list1 = json.loads(text1) len1 = len(list1) print("The list has {0:d} items.".format(len1)) for i1 in list1: print("\t{0:d}".format(i1)) print("done")

Here are some examples of input and output for the above program code.

Here is an example input.
[2, 3, 5, 7, 11]
For the above example input, here is the expected output.
Enter a list in JSON format. You entered "[2, 3, 5, 7, 11]". The list has 5 items. 2 3 5 7 11 done
Here is an example input.
[1, 4, 9, 25, 36, 49, 64, 81, 100, 121, 144, 169]
For the above example input, here is the expected output.
Enter a list in JSON format. You entered "[1, 4, 9, 25, 36, 49, 64, 81, 100, 121, 144, 169]". The list has 12 items. 1 4 9 25 36 49 64 81 100 121 144 169 done