CODEWITHSUNDEEP
python
FJDU
FJDU

Reputation: 1473

How to pause and wait for command input in a Python script

Is it possible to have a script like the following in Python?

...
Pause
->
Wait for the user to execute some commands in the terminal (e.g.
  to print the value of a variable, to import a library, or whatever).
The script will keep waiting if the user does not input anything.
->
Continue execution of the remaining part of the script

Essentially the script gives the control to the Python command line interpreter temporarily, and resume after the user somehow finishes that part.

What I come up with (inspired by the answer) is something like the following:

x = 1

i_cmd = 1
while True:
  s = raw_input('Input [{0:d}] '.format(i_cmd))
  i_cmd += 1
  n = len(s)
  if n > 0 and s.lower() == 'break'[0:n]:
    break
  exec(s)

print 'x = ', x
print 'I am out of the loop.'

Upvotes: 24

Views: 118780

Answers (5)

Thejus Jose
Thejus Jose

Reputation: 21

Simply use the input() function as follows:

# Code to be run before pause
input() # Waits for user to type any character and
        # press Enter or just press Enter twice

# Code to be run after pause

Upvotes: 2

Kelton Temby
Kelton Temby

Reputation: 875

Waiting for user input to 'proceed':

The input function will indeed stop execution of the script until a user does something. Here's an example showing how execution may be manually continued after reviewing pre-determined variables of interest:

var1 = "Interesting value to see"
print("My variable of interest is {}".format(var1))
key_pressed = input('Press ENTER to continue: ')

Proceed after waiting pre-defined time:

Another case I find to be helpful is to put in a delay, so that I can read previous outputs and decide to Ctrl + C if I want the script to terminate at a nice point, but continue if I do nothing.

import time.sleep
var2 = "Some value I want to see"
print("My variable of interest is {}".format(var2))
print("Sleeping for 5 seconds")
time.sleep(5) # Delay for 5 seconds

Actual Debugger for executable Command Line:

Please see answers above on using pdb for stepping through code

Reference: Python’s time.sleep() – Pause, Stop, Wait or Sleep your Python Code

Upvotes: 3

Andy Lorenz
Andy Lorenz

Reputation: 81

The best way I know to do this is to use the pdb debugger. So put

import pdb

at the top of your program, and then use

pdb.set_trace()

for your "pause".

At the (Pdb) prompt you can enter commands such as

(Pdb) print 'x = ', x

and you can also step through code, though that's not your goal here. When you are done simply type

(Pdb) c

or any subset of the word 'continue', and the code will resume execution.

A nice easy introduction to the debugger as of Nov 2015 is at Debugging in Python, but there are of course many such sources if you google 'python debugger' or 'python pdb'.

Upvotes: 8

Cameron Sparr
Cameron Sparr

Reputation: 3981

if you are using Python 2.x: raw_input()

Python 3.x: input()

Example:

# Do some stuff in script
variable = raw_input('input something!: ')
# Do stuff with variable

Upvotes: 41

user3672754
user3672754

Reputation:

I think you are looking for something like this:

import re

# Get user's name
name = raw_input("Please enter name: ")

# While name has incorrect characters
while re.search('[^a-zA-Z\n]',name):

    # Print out an error
    print("illegal name - Please use only letters")

    # Ask for the name again (if it's incorrect, while loop starts again)
    name = raw_input("Please enter name: ")

Upvotes: 2

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