[python] Replace console output in Python

I'm wondering how I could create one of those nifty console counters in Python as in certain C/C++-programs.

I've got a loop doing things and the current output is along the lines of:

Doing thing 0
Doing thing 1
Doing thing 2
...

what would be neater would be to just have the last line update;

X things done.

I've seen this in a number of console programs and am wondering if/how I'd do this in Python.

Below code will count Message from 0 to 137 each 0.3 second replacing previous number.

Number of symbol to backstage = number of digits.

stream = sys.stdout
for i in range(137):
    stream.write('\b' * (len(str(i)) + 10))
    stream.write("Message : " + str(i))
    stream.flush()
    time.sleep(0.3)

The other answer may be better, but here's what I was doing. First, I made a function called progress which prints off the backspace character:

def progress(x):
    out = '%s things done' % x  # The output
    bs = '\b' * 1000            # The backspace
    print bs,
    print out,

Then I called it in a loop in my main function like so:

def main():
    for x in range(20):
        progress(x)
    return

This will of course erase the entire line, but you can mess with it to do exactly what you want. I ended up make a progress bar using this method.

For anyone who stumbles upon this years later (like I did), I tweaked 6502's methods a little bit to allow the progress bar to decrease as well as increase. Useful in slightly more cases. Thanks 6502 for a great tool!

Basically, the only difference is that the whole line of #s and -s is written each time progress(x) is called, and the cursor is always returned to the start of the bar.

def startprogress(title):
    """Creates a progress bar 40 chars long on the console
    and moves cursor back to beginning with BS character"""
    global progress_x
    sys.stdout.write(title + ": [" + "-" * 40 + "]" + chr(8) * 41)
    sys.stdout.flush()
    progress_x = 0


def progress(x):
    """Sets progress bar to a certain percentage x.
    Progress is given as whole percentage, i.e. 50% done
    is given by x = 50"""
    global progress_x
    x = int(x * 40 // 100)                      
    sys.stdout.write("#" * x + "-" * (40 - x) + "]" + chr(8) * 41)
    sys.stdout.flush()
    progress_x = x


def endprogress():
    """End of progress bar;
    Write full bar, then move to next line"""
    sys.stdout.write("#" * 40 + "]\n")
    sys.stdout.flush()

If I understood well (not sure) you want to print using <CR> and not <LR>?

If so this is possible, as long the console terminal allows this (it will break when output si redirected to a file).

from __future__ import print_function
print("count x\r", file=sys.stdout, end=" ")

In python 3 you can do this to print on the same line:

print('', end='\r')

Especially useful to keep track of the latest update and progress.

I would also recommend tqdm from here if one wants to see the progress of a loop. It prints the current iteration and total iterations as a progression bar with an expected time of finishing. Super useful and quick. Works for python2 and python3.

Added a little bit more functionality to the example of Aravind Voggu:

def progressBar(name, value, endvalue, bar_length = 50, width = 20):
        percent = float(value) / endvalue
        arrow = '-' * int(round(percent*bar_length) - 1) + '>'
        spaces = ' ' * (bar_length - len(arrow))
        sys.stdout.write("\r{0: <{1}} : [{2}]{3}%".format(\
                         name, width, arrow + spaces, int(round(percent*100))))
        sys.stdout.flush()
        if value == endvalue:     
             sys.stdout.write('\n\n')

Now you are able to generate multiple progressbars without replacing the previous one.

I've also added name as a value with a fixed width.

For two loops and two times the use of progressBar() the result will look like:

It can be done without using the sys library if we look at the print() function

print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)

Here is my code:

def update(n):
    for i in range(n):
        print("i:",i,sep='',end="\r",flush=True)
        #time.sleep(1)

I wrote this a while ago and really happy with it. Feel free to use it.

It takes an index and total and optionally title or bar_length. Once done, replaces the hour glass with a check-mark.

? Calculating: [¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦] 18.0% done

? Calculating: [¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦] 100.0% done

I included an example that can be run to test it.

import sys
import time

def print_percent_done(index, total, bar_len=50, title='Please wait'):
    '''
    index is expected to be 0 based index. 
    0 <= index < total
    '''
    percent_done = (index+1)/total*100
    percent_done = round(percent_done, 1)

    done = round(percent_done/(100/bar_len))
    togo = bar_len-done

    done_str = '¦'*int(done)
    togo_str = '¦'*int(togo)

    print(f'\t?{title}: [{done_str}{togo_str}] {percent_done}% done', end='\r')

    if round(percent_done) == 100:
        print('\t?')


r = 50
for i in range(r):
    print_percent_done(i,r)
    time.sleep(.02)

I also have a version with responsive progress bar depending on the terminal width using shutil.get_terminal_size() if that is of interest.

A more elegant solution could be:

def progressBar(current, total, barLength = 20):
    percent = float(current) * 100 / total
    arrow   = '-' * int(percent/100 * barLength - 1) + '>'
    spaces  = ' ' * (barLength - len(arrow))

    print('Progress: [%s%s] %d %%' % (arrow, spaces, percent), end='\r')

call this function with value and endvalue, result should be

Progress: [------------->      ] 69 %

Note: Python 2.x version here.