[python] Correct way to pause a Python program

I've been using the input function as a way to pause my scripts:

print("something")
wait = input("Press Enter to continue.")
print("something")

Is there a formal way to do this?

I think that the best way to stop the execution is the time.sleep() function.

If you need to suspend the execution only in certain cases you can simply implement an if statement like this:

if somethinghappen:
    time.sleep(seconds)

You can leave the else branch empty.

cross-platform way; works everywhere

import os, sys

if sys.platform == 'win32':
    os.system('pause')
else:
    input('Press any key to continue...')

I think I like this solution:

import getpass
getpass.getpass("Press Enter to Continue")

It hides whatever the user types in, which helps clarify that input is not used here.

But be mindful on the OS X platform. It displays a key which may be confusing.

Probably the best solution would be to do something similar to the getpass module yourself, without making a read -s call. Maybe making the foreground color match the background?

I have had a similar question and I was using signal:

import signal

def signal_handler(signal_number, frame):
    print "Proceed ..."

signal.signal(signal.SIGINT, signal_handler)
signal.pause()

So you register a handler for the signal SIGINT and pause waiting for any signal. Now from outside your program (e.g. in bash), you can run kill -2 <python_pid>, which will send signal 2 (i.e. SIGINT) to your python program. Your program will call your registered handler and proceed running.

In Linux, you can issue kill -TSTP <pid> to the background and stop a process. So, it's there, but not consuming CPU time.

Then later, kill -CONT <pid> and it's off and running again.

For cross Python 2/3 compatibility, you can use input via the six library:

import six
six.moves.input( 'Press the <ENTER> key to continue...' )

I assume you want to pause without input.

Use:

time.sleep(seconds)

So, I found this to work very well in my coding endeavors. I simply created a function at the very beginning of my program,

def pause():
    programPause = raw_input("Press the <ENTER> key to continue...")

and now I can use the pause() function whenever I need to just as if I was writing a batch file. For example, in a program such as this:

import os
import system

def pause():
    programPause = raw_input("Press the <ENTER> key to continue...")

print("Think about what you ate for dinner last night...")
pause()

Now obviously this program has no objective and is just for example purposes, but you can understand precisely what I mean.

NOTE: For Python 3, you will need to use input as opposed to raw_input

As pointed out by mhawke and steveha's comments, the best answer to this exact question would be:

For a long block of text, it is best to use input('Press <ENTER> to continue') (or raw_input('Press <ENTER> to continue') on Python 2.x) to prompt the user, rather than a time delay. Fast readers won't want to wait for a delay, slow readers might want more time on the delay, someone might be interrupted while reading it and want a lot more time, etc. Also, if someone uses the program a lot, he/she may become used to how it works and not need to even read the long text. It's just friendlier to let the user control how long the block of text is displayed for reading.

Very simple:

raw_input("Press Enter to continue ...")
exit()

I work with non-programmers who like a simple solution:

import code
code.interact(banner='Paused. Press ^D (Ctrl+D) to continue.', local=globals()) 

This produces an interpreter that acts almost exactly like the real interpreter, including the current context, with only the output:

Paused. Press ^D (Ctrl+D) to continue.
>>>

The Python Debugger is also a good way to pause.

import pdb
pdb.set_trace() # Python 2

or

breakpoint() # Python 3

Print ("This is how you pause")

input()

For Windows only, use:

import os
os.system("pause")

By this method, you can resume your program just by pressing any specified key you've specified that:

import keyboard
while True:
    key = keyboard.read_key()
    if key == 'space':  # You can put any key you like instead of 'space'
        break

The same method, but in another way:

import keyboard
while True:
    if keyboard.is_pressed('space'):  # The same. you can put any key you like instead of 'space'
        break

Note: you can install the keyboard module simply by writing this in you shell or cmd:

pip install keyboard

I use the following for Python 2 and Python 3 to pause code execution until user presses Enter

import six

if six.PY2:
    raw_input("Press the <Enter> key to continue...")
else:
    input("Press the <Enter> key to continue...")