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 pision
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 pision
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 pision
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(), ' ',
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(‘ 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