how to remove characters from printed output in python

Question

I am trying to remove extra characters printed out in my print statement from another print statement.

Here is what my code looks like:

print(addedlist)  #addedlist = [9,5,1989,1,2,3,4,5,6,7,8,9]

for x in range(0, len(addedlist)):
    print('%d->'%addedlist[x],end="")

print('\n')

the output of this looks like this:

[9, 5, 1989, 1, 2, 3, 4, 5, 6, 7, 8, 9]
9->5->1989->1->2->3->4->5->6->7->8->9->

I am trying to remove the last -> characters. I tried doing :

print(addedlist)  #addedlist = [9,5,1989,1,2,3,4,5,6,7,8,9]

for x in range(0, len(addedlist)):
     print('%d->'%addedlist[x],end="")

print('\b\b\n')

but it didn't work.

How would i go about accomplishing this ?

EDIT:

Just some clarification, I know i can change my original print statement to print it more correctly to avoid trailing -> ... I am after a solution for how to erase trailing '->' this once the mistake has been made

You'll need something more powerful than just print commands. — unddoch
– unddoch, Commented Apr 18, 2014 at 7:28

zamir · Accepted Answer · 2019-12-02 01:29:11Z

6

I notice you wants to play with carriage return commands. First you need to learn both \b (moves the active position to the previous position) and \r (moves the active position to the start of line) works for current active line.
I think you are working on command line interpreter; at which you explicitly press enter for next line.
On command line interpreter use ; as follows:

>>> print("abb", end=""); print("\b\bcc")
acc
>>> print("a->", end=""); print("\b\b  ")
>>> a

If you are using some script then your code should work, see:

Upload$ cat s.py
print ("abcd->", end="")
print ("\b\b  ")
Upload$ python3.2 s.py
abcd    # notice -> is removed

But this is not much useful, correct approach is what Aशwini चhaudhary has shown in his answer.

Edit: I found you mistake in your code

print('%d->' % addedlist[x], end="")    
print('\b\b\n')

You use '\b' to moves the active position to the previous position, but you don't overwrite "->", you just outputs '\n' that shift cursors to next line, you should rectify your code as below.

print('%d->' % addedlist[x], end="")    
print('\b\b   \n')
#          ^^^  /b then overwrite with spaces

Run at Linux shell as $ python scriptname.py (For command line Python's interpreter you can use something like code I written, it is just to play, use str.join or use sep parameter in print()).

edited Dec 2, 2019 at 1:29

zamir

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answered Apr 18, 2014 at 8:13

Grijesh Chauhan

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4 Comments

sukhvir Over a year ago

thanks mate. Looking at your command line interpreter code, how would you impliment that in my for loop code ?

sukhvir Over a year ago

Thanks a lot.. that helps in command prompt... Why doesn't this work in python shell though ??

Grijesh Chauhan Over a year ago

@sukhvir No it is working on python shell with ; as I shown. Note: on python interpreter you explicitly enters to run a comment that also give newline at output.

Grijesh Chauhan Over a year ago

@sukhvir After playing around 5 min with your code I could write a code for command line interceptor Copy-past this code at Python's command line interpreter that will run like this image

Ashwini Chaudhary · Accepted Answer · 2014-04-18 07:28:44Z

4

Use str.join:

>>> s = [9,5,1989,1,2,3,4,5,6,7,8,9]
>>> print ('->'.join(map(str, s)))
9->5->1989->1->2->3->4->5->6->7->8->9

Or better print() with sep as '->':

>>> print(*s, sep='->')
9->5->1989->1->2->3->4->5->6->7->8->9

answered Apr 18, 2014 at 7:28

Ashwini Chaudhary

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2 Comments

sukhvir Over a year ago

thanks .. I am aware of how to change my print statement to print it correctly .. I am interested in correcting it after wrong printing has been done

Grijesh Chauhan Over a year ago

@sukhvir No once you have printed on stdout you can't overwrite it (if you are not working in curses library). So the answer posted here is exactly do what you wants, otherwise learn ncurses mode.

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