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本文實(shí)例講述了Python顯示進(jìn)度條的方法，是Python程序設(shè)計(jì)中非常實(shí)用的技巧。分享給大家供大家參考。具體方法如下：

首先，進(jìn)度條和一般的print區(qū)別在哪里呢？

答案就是print會(huì)輸出一個(gè)\n，也就是換行符，這樣光標(biāo)移動(dòng)到了下一行行首，接著輸出，之前已經(jīng)通過(guò)stdout輸出的東西依舊保留，而且保證我們?cè)谙旅婵吹阶钚碌妮敵鼋Y(jié)果。

進(jìn)度條不然，我們必須再原地輸出才能保證他是一個(gè)進(jìn)度條，否則換行了怎么還叫進(jìn)度條？

最簡(jiǎn)單的辦法就是，再輸出完畢后，把光標(biāo)移動(dòng)到行首，繼續(xù)在那里輸出更長(zhǎng)的進(jìn)度條即可實(shí)現(xiàn)，新的更長(zhǎng)的進(jìn)度條把舊的短覆蓋，就形成了動(dòng)畫效果。

可以想到那個(gè)轉(zhuǎn)義符了吧，那就是 \r。

轉(zhuǎn)義符\r就可以把光標(biāo)移動(dòng)到行首而不換行，轉(zhuǎn)義符\n就把光標(biāo)移動(dòng)到行首并且換行。

在python中，輸出stdout(標(biāo)準(zhǔn)輸出)可以使用sys.stdout.write
例如：

            
#!/usr/bin/env python
# -*- coding=utf-8 -*-
#Using GPL v2
#Author: ihipop@gmail.com
##2010-10-27 22:07
"""
Usage:
Just A Template
"""
from __future__ import division
 
import sys,time
j = '#'
if __name__ == '__main__':
  for i in range(1,61):
    j += '#'
    sys.stdout.write(str(int((i/60)*100))+'% ||'+j+'->'+"\r")
    sys.stdout.flush()
    time.sleep(0.5)
print

第二種思路是用轉(zhuǎn)義符\b
轉(zhuǎn)義符\b是退格鍵，也就是說(shuō)把輸出的光標(biāo)往回退格子，這樣就可以不用+=了，例如：

            
#!/usr/bin/env python
# -*- coding=utf-8 -*-
#Using GPL v2
#Author: ihipop@gmail.com
#2010-10-27 22:07
"""
Usage:
Just A Template
"""
from __future__ import division
 
import sys,time
if __name__ == '__main__':
  for i in range(1,61):
    sys.stdout.write('#'+'->'+"\b\b")
    sys.stdout.flush()
    time.sleep(0.5)
print

光標(biāo)回退2格，寫個(gè)#再回退，再寫，達(dá)到增長(zhǎng)的目的了

不過(guò)寫這么多似乎是廢話，在耳邊常常聽到一句話：那就是不要重復(fù)造輪子。實(shí)際上python有豐富發(fā)lib幫你實(shí)現(xiàn)這個(gè)東西，你完全可以把心思放在邏輯開發(fā)上而不用注意這些小細(xì)節(jié)

下面要介紹的就是這個(gè)類“progressbar”(http://code.google.com/p/python-progressbar/)，使用easy_install可以方便的安裝這個(gè)類庫(kù)，其實(shí)就一個(gè)文件，拿過(guò)來(lái)放到文件同一個(gè)目錄下面也直接可以import過(guò)來(lái)

如下圖所示：

下面就是基本使用舉例：

            
#!/usr/bin/env python
# -*- coding=utf-8 -*-
#Using GPL v2
#Author: ihipop@gmail.com
#2010-10-27 22:53
"""
Usage:
Just A Template
"""
from __future__ import division
 
import sys,time
from progressbar import *
total = 1000
 
#基本用法
progress = ProgressBar()
for i in progress(range(total)):
 time.sleep(0.01)
 
pbar = ProgressBar().start()
for i in range(1,1000):
  pbar.update(int((i/(total-1))*100))
  time.sleep(0.01)
pbar.finish()
 
#高級(jí)用法
widgets = ['Progress: ', Percentage(), ' ', Bar(marker=RotatingMarker('>-=')),
      ' ', ETA(), ' ', FileTransferSpeed()]
pbar = ProgressBar(widgets=widgets, maxval=10000000).start()
for i in range(1000000):
 # do something
 pbar.update(10*i+1)
 time.sleep(0.0001)
pbar.finish()

官方示例:http://code.google.com/p/python-progressbar/source/browse/progressbar/examples.py

            
#coding:utf-8
import sys
import time
from progressbar import AnimatedMarker, Bar, BouncingBar, Counter, ETA, \
  FileTransferSpeed, FormatLabel, Percentage, \
  ProgressBar, ReverseBar, RotatingMarker, \
  SimpleProgress, Timer

examples = []
def example(fn):
  try: name = 'Example %d' % int(fn.__name__[7:])
  except: name = fn.__name__

  def wrapped():
    try:
      sys.stdout.write('Running: %s\n' % name)
      fn()
      sys.stdout.write('\n')
    except KeyboardInterrupt:
      sys.stdout.write('\nSkipping example.\n\n')

  examples.append(wrapped)
  return wrapped

@example
def example0():
  pbar = ProgressBar(widgets=[Percentage(), Bar()], maxval=300).start()
  for i in range(300):
    time.sleep(0.01)
    pbar.update(i+1)
  pbar.finish()

@example
def example1():
  widgets = ['Test: ', Percentage(), ' ', Bar(marker=RotatingMarker()),
        ' ', ETA(), ' ', FileTransferSpeed()]
  pbar = ProgressBar(widgets=widgets, maxval=10000000).start()
  for i in range(1000000):
    # do something
    pbar.update(10*i+1)
  pbar.finish()

@example
def example2():
  class CrazyFileTransferSpeed(FileTransferSpeed):
    """It's bigger between 45 and 80 percent."""
    def update(self, pbar):
      if 45 < pbar.percentage() < 80:
        return 'Bigger Now ' + FileTransferSpeed.update(self,pbar)
      else:
        return FileTransferSpeed.update(self,pbar)

  widgets = [CrazyFileTransferSpeed(),' <<<', Bar(), '>>> ',
        Percentage(),' ', ETA()]
  pbar = ProgressBar(widgets=widgets, maxval=10000000)
  # maybe do something
  pbar.start()
  for i in range(2000000):
    # do something
    pbar.update(5*i+1)
  pbar.finish()

@example
def example3():
  widgets = [Bar('>'), ' ', ETA(), ' ', ReverseBar('<')]
  pbar = ProgressBar(widgets=widgets, maxval=10000000).start()
  for i in range(1000000):
    # do something
    pbar.update(10*i+1)
  pbar.finish()

@example
def example4():
  widgets = ['Test: ', Percentage(), ' ',
        Bar(marker='0',left='[',right=']'),
        ' ', ETA(), ' ', FileTransferSpeed()]
  pbar = ProgressBar(widgets=widgets, maxval=500)
  pbar.start()
  for i in range(100,500+1,50):
    time.sleep(0.2)
    pbar.update(i)
  pbar.finish()

@example
def example5():
  pbar = ProgressBar(widgets=[SimpleProgress()], maxval=17).start()
  for i in range(17):
    time.sleep(0.2)
    pbar.update(i + 1)
  pbar.finish()

@example
def example6():
  pbar = ProgressBar().start()
  for i in range(100):
    time.sleep(0.01)
    pbar.update(i + 1)
  pbar.finish()

@example
def example7():
  pbar = ProgressBar() # Progressbar can guess maxval automatically.
  for i in pbar(range(80)):
    time.sleep(0.01)

@example
def example8():
  pbar = ProgressBar(maxval=80) # Progressbar can't guess maxval.
  for i in pbar((i for i in range(80))):
    time.sleep(0.01)

@example
def example9():
  pbar = ProgressBar(widgets=['Working: ', AnimatedMarker()])
  for i in pbar((i for i in range(50))):
    time.sleep(.08)

@example
def example10():
  widgets = ['Processed: ', Counter(), ' lines (', Timer(), ')']
  pbar = ProgressBar(widgets=widgets)
  for i in pbar((i for i in range(150))):
    time.sleep(0.1)

@example
def example11():
  widgets = [FormatLabel('Processed: %(value)d lines (in: %(elapsed)s)')]
  pbar = ProgressBar(widgets=widgets)
  for i in pbar((i for i in range(150))):
    time.sleep(0.1)

@example
def example12():
  widgets = ['Balloon: ', AnimatedMarker(markers='.oO@* ')]
  pbar = ProgressBar(widgets=widgets)
  for i in pbar((i for i in range(24))):
    time.sleep(0.3)

@example
def example13():
  # You may need python 3.x to see this correctly
  try:
    widgets = ['Arrows: ', AnimatedMarker(markers='←?I↑?J→?K↓?L')]
    pbar = ProgressBar(widgets=widgets)
    for i in pbar((i for i in range(24))):
      time.sleep(0.3)
  except UnicodeError: sys.stdout.write('Unicode error: skipping example')

@example
def example14():
  # You may need python 3.x to see this correctly
  try:
    widgets = ['Arrows: ', AnimatedMarker(markers='????')]
    pbar = ProgressBar(widgets=widgets)
    for i in pbar((i for i in range(24))):
      time.sleep(0.3)
  except UnicodeError: sys.stdout.write('Unicode error: skipping example')

@example
def example15():
  # You may need python 3.x to see this correctly
  try:
    widgets = ['Wheels: ', AnimatedMarker(markers='????')]
    pbar = ProgressBar(widgets=widgets)
    for i in pbar((i for i in range(24))):
      time.sleep(0.3)
  except UnicodeError: sys.stdout.write('Unicode error: skipping example')

@example
def example16():
  widgets = [FormatLabel('Bouncer: value %(value)d - '), BouncingBar()]
  pbar = ProgressBar(widgets=widgets)
  for i in pbar((i for i in range(180))):
    time.sleep(0.05)

@example
def example17():
  widgets = [FormatLabel('Animated Bouncer: value %(value)d - '),
        BouncingBar(marker=RotatingMarker())]

  pbar = ProgressBar(widgets=widgets)
  for i in pbar((i for i in range(180))):
    time.sleep(0.05)

@example
def example18():
  widgets = [Percentage(),
        ' ', Bar(),
        ' ', ETA(),
        ' ', AdaptiveETA()]
  pbar = ProgressBar(widgets=widgets, maxval=500)
  pbar.start()
  for i in range(500):
    time.sleep(0.01 + (i < 100) * 0.01 + (i > 400) * 0.9)
    pbar.update(i + 1)
  pbar.finish()

@example
def example19():
 pbar = ProgressBar()
 for i in pbar([]):
  pass
 pbar.finish()

try:
  for example in examples:
    example()
except KeyboardInterrupt:
  sys.stdout('\nQuitting examples.\n')

Progress Bar 使用例子

再發(fā)一個(gè)類：

            
#!/usr/bin/env python
# -*- coding=utf-8 -*-
#Using GPL v2
#Author: ihipop@gmail.com
#2010-10-30 13:59
"""
Usage:
Just A Template
"""
class progressbarClass: 
  def __init__(self, finalcount, progresschar=None):
    import sys
    self.finalcount=finalcount
    self.blockcount=0
    #
    # See if caller passed me a character to use on the
    # progress bar (like "*"). If not use the block
    # character that makes it look like a real progress
    # bar.
    #
    if not progresschar: self.block=chr(178)
    else:        self.block=progresschar
    #
    # Get pointer to sys.stdout so I can use the write/flush
    # methods to display the progress bar.
    #
    self.f=sys.stdout
    #
    # If the final count is zero, don't start the progress gauge
    #
    if not self.finalcount : return
    self.f.write('\n------------------- % Progress -------------------\n')
    return
 
  def progress(self, count):
    #
    # Make sure I don't try to go off the end (e.g. >100%)
    #
    count=min(count, self.finalcount)
    #
    # If finalcount is zero, I'm done
    #
    if self.finalcount:
      percentcomplete=int(round(100*count/self.finalcount))
      if percentcomplete < 1: percentcomplete=1
    else:
      percentcomplete=100
      
    #print "percentcomplete=",percentcomplete
    blockcount=int(percentcomplete/2)
    #print "blockcount=",blockcount
    if blockcount > self.blockcount:
      for i in range(self.blockcount,blockcount):
        self.f.write(self.block)
        self.f.flush()
        
    if percentcomplete == 100: self.f.write("\n")
    self.blockcount=blockcount
    return
  
if __name__ == "__main__":
  from time import sleep
  pb=progressbarClass(8,"*")
  count=0
  while count<9:
    count+=1
    pb.progress(count)
    sleep(0.2)

另外，python cookbook中11.1節(jié)也提供了一個(gè)不錯(cuò)的進(jìn)度條類，代碼如下：

            
import sys
class progressbar(object):
  def __init__(self, finalcount, block_char='.'):
    self.finalcount = finalcount
    self.blockcount = 0
    self.block = block_char
    self.f = sys.stdout
    if not self.finalcount: return
    self.f.write('\n------------------ % Progress -------------------1\n')
    self.f.write('  1  2  3  4  5  6  7  8  9  0\n')
    self.f.write('----0----0----0----0----0----0----0----0----0----0\n')
  def progress(self, count):
    count = min(count, self.finalcount)
    if self.finalcount:
      percentcomplete = int(round(100.0*count/self.finalcount))
      if percentcomplete < 1: percentcomplete = 1
    else:
      percentcomplete=100
    blockcount = int(percentcomplete//2)
    if blockcount <= self.blockcount:
      return
    for i in range(self.blockcount, blockcount):
      self.f.write(self.block)
    self.f.flush()
    self.blockcount = blockcount
    if percentcomplete == 100:
      self.f.write("\n")

if __name__ == "__main__":
  from time import sleep
  pb = progressbar(8, "*")
  for count in range(1, 9):
    pb.progress(count)
    sleep(0.2)
  pb = progressbar(100)
  pb.progress(20)
  sleep(0.3)
  pb.progress(47)
  sleep(0.3)
  pb.progress(90)
  sleep(0.3)
  pb.progress(100)
  print "testing 1:"
  pb = progressbar(1)
  pb.progress(1)

運(yùn)行結(jié)果如下圖所示：

希望本文所述對(duì)大家Python程序設(shè)計(jì)的學(xué)習(xí)有所幫助。

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