Print in one line dynamically


Question

I would like to make several statements that give standard output without seeing newlines in between statements.

Specifically, suppose I have:

for item in range(1,100):
    print item

The result is:

1
2
3
4
.
.
.

How get this to instead look like:

1 2 3 4 5 ...

Even better, is it possible to print the single number over the last number, so only one number is on the screen at a time?

1
272
8/6/2014 6:14:58 PM

Accepted Answer

Change print item to:

  • print item, in Python 2.7
  • print(item, end=" ") in Python 3

If you want to print the data dynamically use following syntax:

  • print(item, sep=' ', end='', flush=True) in Python 3
442
11/29/2016 7:47:07 AM

By the way...... How to refresh it every time so it print mi in one place just change the number.

In general, the way to do that is with terminal control codes. This is a particularly simple case, for which you only need one special character: U+000D CARRIAGE RETURN, which is written '\r' in Python (and many other languages). Here's a complete example based on your code:

from sys import stdout
from time import sleep
for i in range(1,20):
    stdout.write("\r%d" % i)
    stdout.flush()
    sleep(1)
stdout.write("\n") # move the cursor to the next line

Some things about this that may be surprising:

  • The \r goes at the beginning of the string so that, while the program is running, the cursor will always be after the number. This isn't just cosmetic: some terminal emulators get very confused if you do it the other way around.
  • If you don't include the last line, then after the program terminates, your shell will print its prompt on top of the number.
  • The stdout.flush is necessary on some systems, or you won't get any output. Other systems may not require it, but it doesn't do any harm.

If you find that this doesn't work, the first thing you should suspect is that your terminal emulator is buggy. The vttest program can help you test it.

You could replace the stdout.write with a print statement but I prefer not to mix print with direct use of file objects.


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