Print the backspace character b several times, and then overwrite the old number with the new number.

Use a terminal-handling library like the curses module:

The curses module provides an interface to the curses library, the de-facto standard for portable advanced terminal handling.

Python 2

I like the following:

print 'Downloading File FooFile.txt [%d%%]r'%i,

Demo:

import time

for i in range(100):
    time.sleep(0.1)
    print 'Downloading File FooFile.txt [%d%%]r'%i,

Python 3

print('Downloading File FooFile.txt [%d%%]r'%i, end="")

Demo:

import time

for i in range(100):
    time.sleep(0.1)
    print('Downloading File FooFile.txt [%d%%]r'%i, end="")

PyCharm Debugger Console with Python 3

# On PyCharm Debugger console, r needs to come before the text.
# Otherwise, the text may not appear at all, or appear inconsistently.
# tested on PyCharm 2019.3, Python 3.6

import time

print('Start.')
for i in range(100):
    time.sleep(0.02)
    print('rDownloading File FooFile.txt [%d%%]'%i, end="")
print('nDone.')

#kinda like the one above but better :P

from __future__ import print_function
from time import sleep

for i in range(101):
  str1="Downloading File FooFile.txt [{}%]".format(i)
  back="b"*len(str1)
  print(str1, end="")
  sleep(0.1)
  print(back, end="")

A neat solution that has been working for me is:

from __future__ import print_function
import sys
for i in range(10**6):
    perc = float(i) / 10**6 * 100
    print(">>> Download is {}% complete      ".format(perc), end='r')
    sys.stdout.flush()
print("")

The sys.stdout.flush is important otherwise it gets really clunky and the print("") on for loop exit is also important.

UPDATE: As mentioned in the comments, print also has a flush argument. So the following will also work:

from __future__ import print_function
for i in range(10**6):
    perc = float(i) / 10**6 * 100
    print(">>> Download is {}% complete      ".format(perc), end='r', flush=True)
print("")

For Python 3xx:

import time
for i in range(10):
    time.sleep(0.2) 
    print ("r Loading... {}".format(i)+str(i), end="")

x="A Sting {}"
   for i in range(0,1000000):
y=list(x.format(i))
print(x.format(i),end="")

for j in range(0,len(y)):
    print("b",end="")

In python 3 the function print can get many arguments.
the full signature of the function print is:
print(args*, sep=' ', end='n', file=sys.stdout, flush=False)

when sep is the separator of the arguments from args*, end is how to end the printed line (‘n means a new line) file is to where print the output (stdout is the consul) and flush is if to clean the buffer.

Usage Example

import sys

a = 'A'
b = 0
c = [1, 2, 3]

print(a, b, c, 4, sep=' * ', end='n' + ('-' * 21), file=sys.stdout, flush=True)

Output

A * 0 * [1, 2, 3] * 4
---------------------

In python there are many ways to format string and even a built in formatted string type.

How to format string

1. the format() function. (some examples)
2. Formatted String Literals or in the common name f-strings.
3. format using % (more about this)

Examples

name = 'my_name'

>>> print('my name is: {}'.format(name))
my name is: my_name

# or
>>> print('my name is: {user_name}'.format(user_name=name))
my name is: my_name

# or
>>> print('my name is: {0}'.format(name))
my name is: my_name

# or using f-strings
>>> print(f'my name is: {name}')
my name is: my_name

# or formatting with %
>>> print('my name is: %s' % name)
my name is: my_name