Python实现控制台进度条功能

本文实例讲述了Python显示进度条的方法，是Python程序设计中非常实用的技巧。分享给大家供大家参考。具体方法如下：

首先，进度条和一般的print区别在哪里呢？

答案就是print会输出一个\n，也就是换行符，这样光标移动到了下一行行首，接着输出，之前已经通过stdout输出的东西依旧保留，而且保证我们在下面看到最新的输出结果。

进度条不然，我们必须再原地输出才能保证他是一个进度条，否则换行了怎么还叫进度条？

最简单的办法就是，再输出完毕后，把光标移动到行首，继续在那里输出更长的进度条即可实现，新的更长的进度条把旧的短覆盖，就形成了动画效果。

可以想到那个转义符了吧，那就是\ r。

转义符r就可以把光标移动到行首而不换行，转义符n就把光标移动到行首并且换行。

在python中，输出stdout(标准输出)可以使用sys.stdout.write
例如：

Python

    #!/usr/bin/env python
    # -*- coding=utf-8 -*-
    #Using GPL v2
    """
    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

第二种思路是用转义符\b
转义符\b是退格键，也就是说把输出的光标往回退格子，这样就可以不用+=了，例如：

Python

    #!/usr/bin/env python
    # -*- coding=utf-8 -*-
    #Using GPL v2
    """
    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

光标回退2格，写个#再回退，再写，达到增长的目的了

不过写这么多似乎是废话，在耳边常常听到一句话：那就是不要重复造轮子。实际上python有丰富发lib帮你实现这个东西，你完全可以把心思放在逻辑开发上而不用注意这些小细节

下面要介绍的就是这个类"progressbar"(http://code.google.com/p/python-progressbar/)，使用easy_install可以方便的安装这个类库，其实就一个文件，拿过来放到文件同一个目录下面也直接可以import过来

如下图所示：

下面就是基本使用举例：

Python

    #!/usr/bin/env python
    # -*- coding=utf-8 -*-
    #Using GPL v2

    """
    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()

    #高级用法
    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

Python

    # 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<a href="http://www.jobbole.com/members/weiboyes8848">@*</a> ')]
      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='<-�↑�->�↓�')]
        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')

再发一个类：

Python

    #!/usr/bin/env python
    # -*- coding=utf-8 -*-
    #Using GPL v2
    """
    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节也提供了一个不错的进度条类，代码如下：

Python

    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)

运行结果如下图所示：

希望本文所述对大家Python程序设计的学习有所帮助。