Python 覆盖 jupyter notebook 中的先前输出
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Overwrite previous output in jupyter notebook
提问by Salvador Dali
Let's assume I have a part of code that runs for some specific amount of time and each 1 second outputs something like this: iteration X, score Y. I will substitute this function with my black box function:
假设我有一个代码一部分的时间一些具体的金额和各1个第二输出端是这样运行的：iteration X, score Y。我将用我的黑盒函数替换这个函数：
from random import uniform
import time
def black_box():
i = 1
while True:
print 'Iteration', i, 'Score:', uniform(0, 1)
time.sleep(1)
i += 1
Now when I run it in Jupyter notebook, it output a new line after each second:
现在，当我在Jupyter notebook 中运行它时，它每秒输出一个新行：
Iteration 1 Score: 0.664167449844
Iteration 2 Score: 0.514757592404
...
Yes, after when the output becomes too big, the html becomes scrollable, but the thing is that I do not need any of these lines except of currently the last one. So instead of having nlines after nseconds, I want to have only 1line (the last one) shown.
是的，当输出变得太大后，html 变得可滚动，但问题是除了当前最后一行之外，我不需要任何这些行。因此，我不想n在n几秒钟后显示行，而是只显示1行（最后一行）。
I have not found anything like this in documentation or looking through magic. A questionwith almost the same title but irrelevant.
我没有在文档或通过魔法寻找任何类似的东西。一个标题几乎相同但无关紧要的问题。
回答by DangerousDave
@cel is right: ipython notebook clear cell output in code
@cel 是对的：ipython notebook 清除代码中的单元格输出
Using the clear_output() gives makes your Notebook have the jitters, though. I recommend using the display() function as well, like this (Python 2.7):
但是，使用 clear_output() 会使您的笔记本产生抖动。我建议也使用 display() 函数，就像这样（Python 2.7）：
from random import uniform
import time
from IPython.display import display, clear_output
def black_box():
i = 1
while True:
clear_output(wait=True)
display('Iteration '+str(i)+' Score: '+str(uniform(0, 1)))
time.sleep(1)
i += 1
回答by chapelo
The usual (documented) way to do what you describe (that only works with Python 3) is:
执行您所描述的操作（仅适用于 Python 3）的常用（已记录）方法是：
print('Iteration', i, 'Score:', uniform(0, 1), end='\r')
In Python 2 we have to sys.stdout.flush()after the print, as it shows in this answer:
在 Python 2 中，我们必须sys.stdout.flush()在打印之后，如本答案所示：
print('Iteration', i, 'Score:', uniform(0, 1), end='\r')
sys.stdout.flush()
Using IPython notebook I had to concatenate the string to make it work:
使用 IPython 笔记本，我必须连接字符串才能使其工作：
print('Iteration ' + str(i) + ', Score: ' + str(uniform(0, 1)), end='\r')
And finally, to make it work with Jupyter, I used this:
最后，为了让它与 Jupyter 一起工作，我使用了这个：
print('\r', 'Iteration', i, 'Score:', uniform(0, 1), end='')
Or you could split the prints before and after the time.sleepif it makes more sense, or you need to be more explicit:
或者print，time.sleep如果更有意义，您可以在s 之前和之后拆分s ，或者您需要更明确：
print('Iteration', i, 'Score:', uniform(0, 1), end='')
time.sleep(1)
print('', end='\r') # or even print('\r', end='')
