jupyter输入，显示，打印执行顺序混乱 [英] jupyter input,display, print excute order is chaotic

问题描述

我正在使用jupyter，而我的python版本是3.5.在while循环中，执行顺序不正确，输入语句在print语句之前.这是我的代码.

I'am using jupyter and my python version is 3.5. In a while loop, excute order is not correct, input statement is before print statement. This is my code.

from IPython.display import display
import pandas as pd
df = pd.DataFrame({'a':[1,2],'b':[3,4]})
while(True):
    a = input("please input:\n")
    display(df.head())
    print (a)

执行结果是

推荐答案

我能够在OSX的Chrome 63下重现该行为.我添加了多个连续的print(a)语句，并且输入字段结尾的位置是随机的:在它们之前，之后或之间.我怀疑每个显示和打印调用都会向服务器发送一个请求，但会异步等待其结果，因此在print(a)的结果准备好之前，可以再次调用input.

I was able to reproduce the behavior under Chrome 63 on OSX. I added several more consecutive print(a) statements and where the input field ends up is random: before them, after them, or in between. My suspicion is that each display and print call sends a request to the server but awaits its result asynchronously, so that input may be called again before the result from print(a) is ready.

这不是一个很好的解决方案，但是在print(a)之后添加一小段睡眠(time.sleep(.02))可以解决我的问题.

It is not an elegant solution, but adding a small sleep (time.sleep(.02)) after print(a) fixes the problem for me.

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