在python中以交互模式执行多行语句 [英] Executing multi-line statements in python in interactive mode

问题描述

我是 Python 世界的新手，这是我的第一个 Python 程序.我来自 R 的世界，所以这对我来说有点不直观.

当我执行

In[15]:导入数学...:随机导入...: random.random()...: math.sqrt(85)...:

在交互模式下(即在 >>> 提示符下)，我得到 math.sqrt() 的输出.我根本没有看到随机数.但是，当我分别执行 random.random() 和 math.sqrt() 时，我确实得到了两个结果.为什么是这样?我如何获得这两个结果?我问这个是因为我有在 R 中选择多行并以交互模式执行它们的习惯，尤其是当我尝试调试代码时.在尝试调试 2000 行代码时，一次只执行一行会很痛苦.

当我在 R 中选择多行然后执行它们时会发生什么:

runif(1,0,1)平方(85)

它会自动解析这些行并生成以下输出:

<代码>>运行(1,0,1)[1] 0.01597949>平方(85)[1] 9.219544

我研究了 SO 并发现 在单行上写多行语句.我不确定如何使用此线程的官方答案.

<小时>

这是 PyCharm 上的输出:

导入数学随机导入random.random()数学.sqrt(85)出[15]:9.219544457292887

我正在寻找某种机制来查看随机数和 85 的 sqrt，而无需添加任何分隔符 、 或 ;，就像我在 R 代码中所做的那样.我很感激任何想法.

预期输入:可以使用 PyCharm 中的使用控制台执行选择"运行代码 [键盘快捷键:Alt + Shift + E]

导入数学随机导入random.random()数学.sqrt(85)

[请注意，我没有使用任何分隔符;"或,"——就像我们在 R 中所做的一样]

预期输出:

random.random()出[16]:0.183145720117748数学.sqrt(85)出[17]:9.219544457292887

解决方案

您可能只看到 math.sqrt() 的输出的原因之一是因为默认情况下 ipython/jupyter 只会为您提供多行命令最后一行的输出.Python 解释器逐行执行代码，任何像 random.random() 这样没有明确打印的语句都会被评估并丢弃.Ipython/Jupyter 默认 获取最后一行的结果并显示它.我没有使用过 pycharm，但它可能会做同样的事情.要查看 random.random() 的输出，您有两个选择:

1) 使用如下所示的打印语句.

在[1]中:导入数学随机导入打印 random.random()数学.sqrt(5)...:0.145504928627出[1]:2.23606797749979在 [2]:

2) 通过更改 ast_node_interactivity 参数来更改默认行为 此处

In [1]: from IPython.core.interactiveshell import InteractiveShell在 [2]: InteractiveShell.ast_node_interactivity = "all"在 [3]:导入数学随机导入random.random()数学.sqrt(5)...:出[3]:0.9772320535532782出[3]:2.23606797749979

IPython 有多种魔法命令，例如 %edit 和 %load，它们允许您直接在您喜欢的编辑器中编辑命令或从文件如下.这可以帮助您选择长代码的特定部分并单独运行它们.下面我将上述行保存在一个名为 test_interpreter.py 的文件中.

在 [1]: !cat test_interpreter.py导入数学随机导入打印 random.random()数学.sqrt(5)在 [2] 中:load -r 1-4 test_interpreter.py在 [3]: # %load -r 1-4 test_interpreter.py导入数学随机导入打印 random.random()数学.sqrt(5)...:0.719244573423出[3]:2.23606797749979

默认情况下，unix shell 中的 python REPL 不支持多行命令(据我所知)，但您可以使用 ; 终止并使用 \ 开始新行code> 是 python REPL 使用的 readline 的转义字符.

<预><代码>>>>导入数学；\... 随机导入；\... random.random();\... math.sqrt(5)0.102984834163726172.23606797749979

在普通的 python 解释器和 ipython 中，您可以直接从编辑器中复制粘贴行，它们将像下面一样单独评估.

#复制粘贴四行>>>导入数学>>>随机导入>>>random.random()0.16039452147586075>>>数学.sqrt(5)2.23606797749979

I am new to the world of Python, and this is my first program in Python. I come from the world of R so this is a bit unintuitive to me.

When I execute

In[15]: import math
   ...: import random
   ...: random.random()
   ...: math.sqrt(85)
   ...: 

in interactive mode (i.e. on >>> prompt), I get the output of math.sqrt(). I don't see the random number at all. However, when I execute random.random() and math.sqrt() separately, I do get both the results. Why is this? How do I get both the results? I am asking this because I have the habit of selecting multiple lines in R and executing them in interactive mode, especially when I am trying to debug code. Executing only one line at a time will be excruciating when trying to debug, say, 2000-line code.

Here's what happens when I select multiple lines in R and then execute them:

runif(1,0,1)
  sqrt(85)

It automatically parses these lines and generates the following output:

> runif(1,0,1)
[1] 0.01597949
>   sqrt(85)
[1] 9.219544

I researched on SO and found Write multi-line statement on single line. I am unsure how to use the official answer from this thread.

---

Here's the output on PyCharm:

import math
import random
random.random()
math.sqrt(85)
Out[15]: 9.219544457292887

I am looking for some mechanism to see a random number and the sqrt of 85 without having to add any separator , or ;, as I did in R code. I'd appreciate any thoughts.

Expected Input: One would run the code using "Execute Selection using Console" in PyCharm [Keyboard Shortcut: Alt + Shift + E]

import math
import random
random.random()
math.sqrt(85)

[Please note that I haven't used any separator ";" or ","--just as we do in R]

Expected Output:

random.random()
Out[16]: 0.183145720117748
math.sqrt(85)
Out[17]: 9.219544457292887

解决方案

One of the reasons you are probably seeing the output of math.sqrt() only is because by default ipython/jupyter will only give you output of the last line of a multiline command. Python interpreter executes code line by line and any statement like random.random() which are not explicitly printed are just evaluated and thrown away. Ipython/Jupyter by default gets the result of the last line and displays it. I have not used pycharm but it probably does the same thing. To see the output of random.random() you have two options:

1) Use a print statement like below.

In [1]: import math
import random
print random.random()
math.sqrt(5)
   ...: 
0.145504928627
Out[1]: 2.23606797749979

In [2]: 

2) Change the default behavior by changing the ast_node_interactivity parameter as answered here

In [1]: from IPython.core.interactiveshell import InteractiveShell

In [2]: InteractiveShell.ast_node_interactivity = "all"

In [3]: import math
import random
random.random()
math.sqrt(5)
   ...: 
Out[3]: 0.9772320535532782
Out[3]: 2.23606797749979

IPython has a variety of magic commands like %edit and %load which allows you to directly edit the commands in your favorite editor or load specific lines of code from a file like below. This can help with your requirement of selecting specific sections of your long code and running them separately. Below I have saved the above lines in a file called test_interpreter.py.

In [1]: !cat test_interpreter.py
import math
import random
print random.random()
math.sqrt(5)

In [2]: load -r 1-4 test_interpreter.py

In [3]: # %load -r 1-4 test_interpreter.py
import math
import random
print random.random()
math.sqrt(5)
   ...: 
0.719244573423
Out[3]: 2.23606797749979

The python REPL in unix shells by default does not support multiline commands (as far as I know of) but you can use ; to terminate and start a new line with \ which is escape character for readline which python REPL uses.

>>> import math;\
... import random;\
... random.random();\
... math.sqrt(5)
0.10298483416372617
2.23606797749979

In both normal python interpreter and ipython you can however directly copy paste lines from your editor and they will be evaluated separately like below.

#Copy paste four lines together
>>> import math
>>> import random
>>> random.random()
0.16039452147586075
>>> math.sqrt(5)
2.23606797749979

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