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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
</div>
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
</div>
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()
</div>
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='◐◓◑`