python2.7 print函數(shù)中\(zhòng)r的作用

這是搜索到的一段progress bar的代碼:

from __future__ import print_function
# Print iterations progress
def printProgressBar (iteration, total, prefix = '', suffix = '', decimals = 1, length = 100, fill = '|'):
    """
    Call in a loop to create terminal progress bar
    @params:
        iteration   - Required  : current iteration (Int)
        total       - Required  : total iterations (Int)
        prefix      - Optional  : prefix string (Str)
        suffix      - Optional  : suffix string (Str)
        decimals    - Optional  : positive number of decimals in percent complete (Int)
        length      - Optional  : character length of bar (Int)
        fill        - Optional  : bar fill character (Str)
    """
    percent = ("{0:." + str(decimals) + "f}").format(100 * (iteration / float(total)))
    filledLength = int(length * iteration // total)
    bar = fill * filledLength + '-' * (length - filledLength)
    print('\r%s |%s| %s%% %s' % (prefix, bar, percent, suffix), end = '\r')
    # Print New Line on Complete
    if iteration == total:
        print()
from time import sleep

# A List of Items
items = list(range(0, 57))
l = len(items)

# Initial call to print 0% progress
printProgressBar(0, l, prefix = 'Progress:', suffix = 'Complete', length = 50)

print('\r%s |%s| %s%% %s' % (prefix, bar, percent, suffix), end = '\r')

這里的 第一個(gè) \r 起到了什么作用呢？ 我知道這個(gè)是讓光標(biāo)回到行首 這個(gè)end='r'不是已經(jīng)在每一行都做這個(gè)操作了嗎？

另外：如果去掉第一個(gè)r 也能顯示進(jìn)度條 但是很不流暢，好像緩沖區(qū)沒有在每一次print的時(shí)候清空，難道r還有清空緩沖區(qū)的作用？