Command line input in Python

Question

Is it possible to run first the program then wait for the input of the user in command line. e.g.

Run...

Process...

Input from the user(in command line form)...

Process...

Answer 1

It is not at all clear what the OP meant (even after some back-and-forth in the comments), but here are two answers to possible interpretations of the question:

For interactive user input (or piped commands or redirected input)

Use raw_input in Python 2.x, and input in Python 3. (These are built in, so you don't need to import anything to use them; you just have to use the right one for your version of python.)

For example:

user_input = raw_input("Some input please: ")

More details can be found here.

So, for example, you might have a script that looks like this

# First, do some work, to show -- as requested -- that
# the user input doesn't need to come first.
from __future__ import print_function
var1 = 'tok'
var2 = 'tik'+var1
print(var1, var2)

# Now ask for input
user_input = raw_input("Some input please: ") # or `input("Some...` in python 3

# Now do something with the above
print(user_input)

If you saved this in foo.py, you could just call the script from the command line, it would print out tok tiktok, then ask you for input. You could enter bar baz (followed by the enter key) and it would print bar baz. Here's what that would look like:

$ python foo.py
tok tiktok
Some input please: bar baz
bar baz

Here, $ represents the command-line prompt (so you don't actually type that), and I hit Enter after typing bar baz when it asked for input.

For command-line arguments

Suppose you have a script named foo.py and want to call it with arguments bar and baz from the command line like

$ foo.py bar baz

(Again, $ represents the command-line prompt.) Then, you can do that with the following in your script:

import sys
arg1 = sys.argv[1]
arg2 = sys.argv[2]

Here, the variable arg1 will contain the string 'bar', and arg2 will contain 'baz'. The object sys.argv is just a list containing everything from the command line. Note that sys.argv[0] is the name of the script. And if, for example, you just want a single list of all the arguments, you would use sys.argv[1:].