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：
#!/usr/bin/env python# -*- coding=utf-8 -*-#using gpl v2#author: ihipop@gmail.com##2010-10-27 22:07usage:just a templatefrom __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+'->'+\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：
#!/usr/bin/env python# -*- coding=utf-8 -*-#using gpl v2#author: ihipop@gmail.com#2010-10-27 22:07usage:just a templatefrom __future__ import division import sys,timeif __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：
#!/usr/bin/env python# -*- coding=utf-8 -*-#using gpl v2#author: ihipop@gmail.com#2010-10-27 22:53usage:just a templatefrom __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()
官方示例:http://code.google.com/p/python-progressbar/source/browse/progressbar/examples.py
#coding:utf-8import sysimport timefrom progressbar import animatedmarker, bar, bouncingbar, counter, eta, \ filetransferspeed, formatlabel, percentage, \ progressbar, reversebar, rotatingmarker, \ simpleprogress, timerexamples = []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@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 < pbar.percentage() < 80: return 'bigger now ' + filetransferspeed.update(self,pbar) else: return filetransferspeed.update(self,pbar) widgets = [crazyfiletransferspeed(),' ', 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('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(\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：
import sysclass 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。