Python在Console下显示文本进度条的方法
进度条实现原理
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？
实现进度条最简单的办法就是，在输出完毕后，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。
在用Python处理耗时的任务时，往往希望能够了解到任务当前的处理进度，这个时候需要在任务中不断打印出任务的进度信息。一般我们是这样的：
def process_mission():
""" 任务处理方法 """
# 这里是任务处理过程
print('当前处理到第[%d]项' % count)
# 这里是任务处理过程
这种方式会在窗口输出一堆类似下面这样的信息：
当前处理到第1项
当前处理到第2项
当前处理到第3项
当前处理到第4项
当前处理到第5项
....
这种信息有可能非常非常的长，也有可能输出的时候非常非常的快，以至于根本就无法看清楚(输出非常快的时候)。
这时候，我们期待这样的功能：
[================== ] 25.60%
但如果纯粹的使用 print 是无法达到效果的，会变成和前面一样，满屏都是这种杠杠。
如何正确显示进度条呢？
Python提供了一个模块，叫： progressbar ，当使用这个模块之后，你要显示进度的仅需如下：
import progressbar
# 先定义一个进度条
# http://blog.useasp.net/
pbar = progressbar.ProgressBar(maxval=100, \
widgets=[progressbar.Bar('=', '[', ']'), ' ', \
progressbar.Percentage()])
for i in xrange(100):
# 更新进度条
pbar.update(i+1)
pbar.finish()# Ok，到此完结。
是不是很容易就完成进度条的显示？不过遗憾的是，这个python模块并不是默认的，而是需要安装：
pip install progressbar
如果没有安装 pip 可以 参考这里 。
对于只要一个简单进度条的人来说，安装个python包似乎有点动静太大，那么，自己动手写一个便是了。
下面是Mitchell自己写的一个类似的进度条，不用安装包，简单易用。
# 在使用本方法之前，请先做如下import
# from __future__ import division
# import math
# import sys
# ##blog.useasp.net##
def progressbar(cur, total):
percent = '{:.2%}'.format(cur / total)
sys.stdout.write('\r')
sys.stdout.write("[%-50s] %s" % (
'=' * int(math.floor(cur * 50 / total)),
percent))
sys.stdout.flush()说明：
cur , total ：一个是当前值，一个是总值。 cur 在任务的处理过程中会不断向 total 靠近，直到两者相等，任务结束
需要注意的是，这两个可能为整型，因此要引入 division 。
在使用的时候，只需要调用 progressbar 即可在控制台输出进度条。
# 调用方式举例 progressbar(2, 100) progressbar(3.9, 10) progressbar(3283, 27379)
到此，我们完成了一个会在控制台动态更新的进度条。
以上所述是小编给大家介绍的Python在Console下显示文本进度条的方法，希望对大家有所帮助。
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