python - Remove and Replace Printed items

137
votes

I was wondering if it was possible to remove items you have printed in Python - not from the Python GUI, but from the command prompt. e.g.

a = 0  
for x in range (0,3):  
    a = a + 1  
    b = ("Loading" + "." * a)
print (a)

so it prints

>>>Loading   
>>>Loading. 
>>>Loading.. 
>>>Loading...

But, my problem is I want this all on one line, and for it it remove it self when something else comes along. So instead of printing "Loading", "Loading.", "Loading... I want it to print "Loading.", then it removes what is on the line and replaces it with "Loading.." and then removes "Loading.." and replaces it (on the same line) with "Loading...". It's kind of hard to describe.

p.s I have tried to use the Backspace character but it doesn't seem to work ("\b")

Thanks

3
pythonpython-3.xprintingpython-3.2
Whats the point of the a variable here? You can just use x as your variable and it will do the same thing! - John Howard
Two questions: 1. shouldn't be the print() command indentet to the level of the inner of the for-loop? Currently, your code doesn't print some kind of progress, but only the final state. 2. shouldn't it be print (b)? Currently only integers are printed, not the "Loading" as mentioned in the question. - Qaswed

3 Answers

209
votes

Just use CR to go to beginning of the line.

import time
for x in range (0,5):  
    b = "Loading" + "." * x
    print (b, end="\r")
    time.sleep(1)
117
votes

One way is to use ANSI escape sequences:

import sys
import time
for i in range(10):
    print("Loading" + "." * i)
    sys.stdout.write("\033[F") # Cursor up one line
    time.sleep(1)

Also sometimes useful (for example if you print something shorter than before):

sys.stdout.write("\033[K") # Clear to the end of line
30
votes
import sys
import time

a = 0  
for x in range (0,3):  
    a = a + 1  
    b = ("Loading" + "." * a)
    # \r prints a carriage return first, so `b` is printed on top of the previous line.
    sys.stdout.write('\r'+b)
    time.sleep(0.5)
print (a)

Note that you might have to run sys.stdout.flush() right after sys.stdout.write('\r'+b) depending on which console you are doing the printing to have the results printed when requested without any buffering.