[Tutor] Console output

[Roel Schroeven]

Oliver Maunder wrote:
> Does anyone know how I can update a line of console output without
> creating a new line? I'm not explaning this too well, so here's an example.
> 
> When you download a file with wget, the console display looks like this:
> 
> 14% [=======>                                                    ]
> 344,192       16.28K/s    ETA 02:19
> 
> All the figures and the progress bar get continously updated. The only
> way I know of sending output to the console is to use print or
> sys.stdout.write(), but that would give me:
> 14% [=======>                                                    ]
> 344,192       16.28K/s    ETA 02:19
> 18% [=========>                                               ]
> 344,192       16.28K/s    ETA 02:19
> 20% [============>                                                ]
> 344,192       16.28K/s    ETA 02:19
> 
> ...and that's really not what I'm after!
> 
> Any help and ideas would be appreciated

You need to:
- not write a newline
- backup to the beginning of the line

Simple example:

import sys
import time

def progress(n):
    for i in range(n+1):
        sys.stdout.write('\r%3s%% [%s>%s]' % (i, '='*i, ' '*(n-i)))
        sys.stdout.flush()
        time.sleep(0.5)

progress(60)

No newline is written, and the program backs up to the beginning of the
line using carriage return, '\r'. You can also put the carriage return
at the end of the line; the difference is that the cursor will be left
at the beginning of the line instead of at the end.

It's also possible to back up using backspaces ('\b'), but then you need
to count how many characters you wrote and use the equal amount of
backslashes.

-- 
If I have been able to see further, it was only because I stood
on the shoulders of giants.  -- Isaac Newton

Roel Schroeven