Print in one line dynamically

Question

I would like to make several statements that give standard output without seeing newlines in between statements.

Specifically, suppose I have:

for item in range(1,100):
    print item

The result is:

1
2
3
4
.
.
.

How get this to instead look like:

1 2 3 4 5 ...

Even better, is it possible to print the single number over the last number, so only one number is on the screen at a time?

Solution 1

Change print item to:

• print item, in Python 2.7
• print(item, end=" ") in Python 3

If you want to print the data dynamically use following syntax:

• print(item, sep=' ', end='', flush=True) in Python 3

Solution 2

By the way...... How to refresh it every time so it print mi in one place just change the number.

In general, the way to do that is with terminal control codes. This is a particularly simple case, for which you only need one special character: U+000D CARRIAGE RETURN, which is written '\r' in Python (and many other languages). Here's a complete example based on your code:

from sys import stdout
from time import sleep
for i in range(1,20):
    stdout.write("\r%d" % i)
    stdout.flush()
    sleep(1)
stdout.write("\n") # move the cursor to the next line

Some things about this that may be surprising:

• The \r goes at the beginning of the string so that, while the program is running, the cursor will always be after the number. This isn't just cosmetic: some terminal emulators get very confused if you do it the other way around.
• If you don't include the last line, then after the program terminates, your shell will print its prompt on top of the number.
• The stdout.flush is necessary on some systems, or you won't get any output. Other systems may not require it, but it doesn't do any harm.

If you find that this doesn't work, the first thing you should suspect is that your terminal emulator is buggy. The vttest program can help you test it.

You could replace the stdout.write with a print statement but I prefer not to mix print with direct use of file objects.

Solution 3

Use print item, to make the print statement omit the newline.

In Python 3, it's print(item, end=" ").

If you want every number to display in the same place, use for example (Python 2.7):

to = 20
digits = len(str(to - 1))
delete = "\b" * (digits + 1)
for i in range(to):
    print "{0}{1:{2}}".format(delete, i, digits),

In Python 3, it's a bit more complicated; here you need to flush sys.stdout or it won't print anything until after the loop has finished:

import sys
to = 20
digits = len(str(to - 1))
delete = "\b" * (digits)
for i in range(to):
   print("{0}{1:{2}}".format(delete, i, digits), end="")
   sys.stdout.flush()

Solution 4

Like the other examples,
I use a similar approach but instead of spending time calculating out the last output length, etc,

I simply use ANSI code escapes to move back to the beginning of the line and then clear that entire line before printing my current status output.

import sys

class Printer():
    """Print things to stdout on one line dynamically"""
    def __init__(self,data):
        sys.stdout.write("\r\x1b[K"+data.__str__())
        sys.stdout.flush()

To use in your iteration loop you would just call something like:

x = 1
for f in fileList:
    ProcessFile(f)
    output = "File number %d completed." % x
    Printer(output)
    x += 1   

See more here

Solution 5

change

print item

to

print "\033[K", item, "\r",
sys.stdout.flush()

• "\033[K" clears to the end of the line
• the \r, returns to the beginning of the line
• the flush statement makes sure it shows up immediately so you get real-time output.

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