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，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。
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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,timej = '#'if __name__ == '__main__': for i in range(1,61): j += '#' sys.stdout.write(str(int((i/60)*100))+'% ||'+j+'->'+"") sys.stdout.flush() time.sleep(0.5)print
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第二种思路是用转义符
转义符是退格键，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,timeif __name__ == '__main__': for i in range(1,61): sys.stdout.write('#'+'->'+"") sys.stdout.flush() time.sleep(0.5)print
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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,timefrom 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()
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官方示例:http://code.google.com/p/python-progressbar/source/browse/progressbar/examples.py
Python
# coding:utf-8import sysimport timefrom 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' % name) fn() sys.stdout.write('') except KeyboardInterrupt: sys.stdout.write('Skipping example.') examples.append(wrapped) return wrapped @exampledef example0(): pbar = ProgressBar(widgets=[Percentage(), Bar()], maxval=300).start() for i in range(300): time.sleep(0.01) pbar.update(i + 1) pbar.finish() @exampledef 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() @exampledef example2(): class CrazyFileTransferSpeed(FileTransferSpeed): """It's bigger between 45 and 80 percent.""" def update(self, pbar): if 45 >> ', 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() @exampledef example3(): widgets = [Bar('>'), ' ', ETA(), ' ', ReverseBar('@* ')] pbar = ProgressBar(widgets=widgets) for i in pbar((i for i in range(24))): time.sleep(0.3) @exampledef 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') @exampledef 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') @exampledef 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') @exampledef 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) @exampledef 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) @exampledef example18(): widgets = [Percentage(), ' ', Bar(), ' ', ETA(), ' ', AdaptiveETA()] pbar = ProgressBar(widgets=widgets, maxval=500) pbar.start() for i in range(500): time.sleep(0.01 + (i 400) * 0.9) pbar.update(i + 1) pbar.finish() @exampledef example19(): pbar = ProgressBar() for i in pbar([]): pass pbar.finish() try: for example in examples: example()except KeyboardInterrupt: sys.stdout('Quitting examples.')
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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('------------------- % Progress -------------------') 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 self.blockcount: for i in range(self.blockcount,blockcount): self.f.write(self.block) self.f.flush() if percentcomplete == 100: self.f.write("") self.blockcount=blockcount return if __name__ == "__main__": from time import sleep pb=progressbarClass(8,"*") count=0 while count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('------------------ % Progress -------------------1') self.f.write(' 1 2 3 4 5 6 7 8 9 0') self.f.write('----0----0----0----0----0----0----0----0----0----0') def progress(self, count): count = min(count, self.finalcount) if self.finalcount: percentcomplete = int(round(100.0 * count / self.finalcount)) if percentcomplete 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。
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