Print to the same line and not a new line in pytho

问题:

Basically I want to do the opposite of what this guy did... hehe.

Python Script: Print new line each time to shell rather than update existing line

I have a program that is telling me how far along it is.

for i in some_list:
    #do a bunch of stuff.
    print i/len(some_list)*100," percent complete"

So if len(some_list) was 50, I'd get that last line printed 50 times over. I want to print one line and keep updating that line. I know I know this is probably the lamest question you'll read all day. I just can't figure out the four words I need to put into google to get the answer.

Update! I tried mvds' suggestion which SEEMED right. The new code

print percent_complete,"           \r",

Percent complete is just a string (I was abstracting the first time now I an trying to be literal). The result now is that it runs the program, doesn't print ANYTHING until after the program is over, and then prints "100 percent complete" on one and only one line.

Without the carriage return (but with the comma, half of mvds' suggestion) it prints nothing until the end. And then prints:

0 percent complete     2 percent complete     3 percent complete     4 percent complete    

And so on. So now the new issue is that with the comma it doesn't print until the program is finished.

With the carriage return and no comma it behaves the exact same as with neither.

回答1:

It's called the carriage return, or \r

Use

print i/len(some_list)*100," percent complete         \r",

The comma prevents print from adding a newline. (and the spaces will keep the line clear from prior output)

Also, don't forget to terminate with a print "" to get at least a finalizing newline!

回答2:

From python 3.x you can do:

print('bla bla', end='')

(which can also be used in Python 2.6 or 2.7 by putting from __future__ import print_function at the top of your script/module)

Python console progressbar example:

import time

# status generator
def range_with_status(total):
    """ iterate from 0 to total and show progress in console """
    n=0
    while n<total:
        done = '#'*(n+1)
        todo = '-'*(total-n-1)
        s = '<{0}>'.format(done+todo)
        if not todo:
            s+='\n'        
        if n>0:
            s = '\r'+s
        print(s, end='')
        yield n
        n+=1

# example for use of status generator
for i in range_with_status(10):
    time.sleep(0.1)

回答3:

For me, what worked was a combo of Remi's and siriusd's answers:

from __future__ import print_function
import sys

print(str, end='\r')
sys.stdout.flush()

回答4:

for Console you'll probably need

sys.stdout.flush()

to force update. I think using , in print will block stdout from flushing and somehow it won't update

回答5:

This works for me, hacked it once to see if it is possible, but never actually used in my program (GUI is so much nicer):

import time
f = '%4i %%'
len_to_clear = len(f)+1
clear = '\x08'* len_to_clear
print 'Progress in percent:'+' '*(len_to_clear),
for i in range(123):
    print clear+f % (i*100//123),
    time.sleep(0.4)
raw_input('\nDone')

回答6:

Nobody has mentioned that in Python 3(.something?) you don't need sys.stdout.flush(). print('foobar', end='', flush=True) works.

回答7:

Try it like this:

for i in some_list:
    #do a bunch of stuff.
    print i/len(some_list)*100," percent complete",

(With a comma at the end.)

回答8:

import time
import sys


def update_pct(w_str):
    w_str = str(w_str)
    sys.stdout.write("\b" * len(w_str))
    sys.stdout.write(" " * len(w_str))
    sys.stdout.write("\b" * len(w_str))
    sys.stdout.write(w_str)
    sys.stdout.flush()

for pct in range(0, 101):
    update_pct("{n}%".format(n=str(pct)))
    time.sleep(0.1)

\b will move the location of the cursor back one space
So we move it back all the way to the beginning of the line
We then write spaces to clear the current line - as we write spaces the cursor moves forward/right by one
So then we have to move the cursor back at the beginning of the line before we write our new data

Tested on Windows cmd using Python 2.7

回答9:

Based on Remi answer for Python 2.7+ use this:

from __future__ import print_function
import time

# status generator
def range_with_status(total):
    """ iterate from 0 to total and show progress in console """
    import sys
    n = 0
    while n < total:
        done = '#' * (n + 1)
        todo = '-' * (total - n - 1)
        s = '<{0}>'.format(done + todo)
        if not todo:
            s += '\n'
        if n > 0:
            s = '\r' + s
        print(s, end='\r')
        sys.stdout.flush()
        yield n
        n += 1


# example for use of status generator
for i in range_with_status(50):
    time.sleep(0.2)