转换逗号分隔的字符串到numpy的阵列在Python 3

我使用Python来从在Python 3.转换逗号分隔的字符串到numpy的阵列在Python 3

使用PySerial我要绘制使用PyQtGraph数据一个Arduino传感器读出的数据，所以我试图将从传感器读取的字符串（288个逗号分隔值）转换为Numpy数组。但是，我尝试了几种不同的方法，并没有得到它的工作。

从传感器读取的伟大工程与此代码：

#Read the line of data from the sensor 
line = sensor.readline() 

#Decode the line to UTF-8 and print it 
lineDecoded = line.decode("UTF-8") 

print(lineDecoded)

这给了我正确的输出（288逗号分隔值）：

137,136,151,145,141,133,145,139,140,145,144,139,143,141,139,136,137,138,137,127,142,135,136,137,134,140,127,141,134,128,139,135,136,180,149,147,147,151,156,140,153,143,143,155,163,164,192,250,277,282,275,258,258,248,245,231,215,225,195,195,159,186,175,168,171,173,177,185,213,224,228,231,227,219,261,229,231,231,250,253,262,276,269,274,274,277,276,272,291,303,351,417,483,500,473,399,315,263,255,239,238,244,234,231,231,242,255,272,294,293,299,314,307,306,302,310,319,304,312,327,370,464,507,514,492,425,358,327,313,299,292,291,281,259,245,232,229,224,223,222,216,226,215,211,197,202,199,197,198,193,198,185,190,196,177,198,188,183,201,193,187,159,189,184,186,185,186,185,184,196,195,200,201,198,193,241,189,186,167,179,187,174,188,180,179,169,177,173,172,175,181,175,171,180,175,176,180,184,176,190,182,172,171,179,178,174,188,175,178,167,183,171,168,174,175,171,230,175,177,159,177,170,172,171,173,168,167,169,172,168,171,177,173,167,167,171,163,170,177,172,169,167,163,157,173,161,168,174,162,165,171,165,162,152,165,173,158,193,161,161,147,159,161,159,169,173,168,158,161,159,158,171,167,167,155,159,169,156,159,162,157,165,161,158,147,161,171,159,

从那里，想我会只是能够通过lineDecoded到PyQtGraph的plot功能，但运行后这行代码

x = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251,252,253,254,255,256,257,258,259,260,261,262,263,264,265,266,267,268,269,270,271,272,273,274,275,276,277,278,279,280,281,282,283,284,285,286,287,288] 

y = [lineDecoded] 

#Plot the data 
pg.plot(x, y)

我得到了错误Exception: X and Y arrays must be the same shape--got (288,) and (1,).

我尝试使用像np.fromstring(lineDecoded)和np.array(list(lineDecoded)).ravel()但没有我试过的工作方法，各种方法将它传递给PyQtGraph之前转换的字符串。

关于如何完成这个任何想法？

编辑：我已经经历了答案，他们似乎都没有工作，每个回复的评论中的细节。任何提示都会很棒。

来源

2017-04-19 AggroCrag

你可以做一个打印y和输入（y），输出是什么？ – Allen

你可以将它分割成一个列表，然后分割成一个numpy.array，'y = np.array（lineDecoded.split（“，”））'。但是，并不一定要将它用作绘图列表。 – umutto

line.decode（）返回一个字符串，而不是一个列表。所以你回来了一个单一的实体，而不是288个值。

Python有一个与字符串关联的方法，它会接受一个字符串并将其分解为组成部分。调用.split（）方法并为其分配子字符串，在这种情况下，'，'应该做的伎俩。

#Read the line of data from the sensor 
line = sensor.readline() 

#Decode the line to UTF-8 and print it 
lineDecoded = line.decode("UTF-8") 


values = [int(i) for i in lineDecoded.split(',')] # <<< this should work 
                # added a list 
                # comprehension to 
                # convert values to integers 


x = range(1,289)     # <<< this is preferred if you need 
            # a range of numbers from 1 to 288 

y = values 

#Plot the data 
pg.plot(x, y)

注：如@umutto提到了上述评论，密谋目的，应该没有必要的值转换为numpy的阵列。列表应该没问题。

但是，如果由于某种原因，你会发现你想/需要一个数组： Y = np.array（值）

来源

2017-04-19 07:12:47

谢谢 - 我用你的建议在分裂功能，并得到了'TypeError：不能执行减少与灵活类型pyqtgraph'，所以我修改了'lineDecoded = lineDecoded [： - 2]'（删除多余的数字）和'yValues = lineDecoded.split（“，”）''y = np.array（yValues）.astype（np.int）'。错误信息现在消失了，但PyQtGraph弹出窗口在打开时崩溃并且不显示任何数据。任何想法为什么会发生（在Jupyter）？ – AggroCrag

@AggroCrag的问题：您可以使用简单的，定义明确的数据来生成您试图生成的图的简化版本吗？即饲料到pg.plot（x，y）每个短列表： x = [1,2,3] y = [5,6,7] 我经常通过创建我的问题的来源众所周知的数据，看看是否有效。如果是这样，那么我开始看看我的真实数据。如果没有，那么我开始看看我的实现（即Jupyter设置为显示PyQtGraphs等等）。对不起，我不能更具体。注意：我们的答案在解决提出的原始问题方面似乎令人满意。 –

我继续前进并使用您提到的代码，并且弹出该简单数据集的Python窗口也崩溃了。必须是我的一个系统问题。谢谢！ – AggroCrag

lineDecoded = [137,136,151,145,141,133,145,139,140,145,144,139,143,141,139,136,137,138,137,127,142,135,136,137,134,140,127,141,134,128,139,135,136,180,149,147,147,151,156,140,153,143,143,155,163,164,192,250,277,282,275,258,258,248,245,231,215,225,195,195,159,186,175,168,171,173,177,185,213,224,228,231,227,219,261,229,231,231,250,253,262,276,269,274,274,277,276,272,291,303,351,417,483,500,473,399,315,263,255,239,238,244,234,231,231,242,255,272,294,293,299,314,307,306,302,310,319,304,312,327,370,464,507,514,492,425,358,327,313,299,292,291,281,259,245,232,229,224,223,222,216,226,215,211,197,202,199,197,198,193,198,185,190,196,177,198,188,183,201,193,187,159,189,184,186,185,186,185,184,196,195,200,201,198,193,241,189,186,167,179,187,174,188,180,179,169,177,173,172,175,181,175,171,180,175,176,180,184,176,190,182,172,171,179,178,174,188,175,178,167,183,171,168,174,175,171,230,175,177,159,177,170,172,171,173,168,167,169,172,168,171,177,173,167,167,171,163,170,177,172,169,167,163,157,173,161,168,174,162,165,171,165,162,152,165,173,158,193,161,161,147,159,161,159,169,173,168,158,161,159,158,171,167,167,155,159,169,156,159,162,157,165,161,158,147,161,171,159] 

x = range(1,289) 
import matplotlib.pyplot as plt 
plt.plot(x, lineDecoded)

来源

2017-04-19 07:12:35 Allen

使用的线转换为字符串的list的str.split方法。同样如@Alien所示，您应该使用函数获取x，而不是手动枚举所有值。

y = [int(i) for i in lineDecoded.split(',')] 
x = range(1,289) 

import matplotlib.pyplot as plt 
fig = plt.figure() 
plt.plot(x, lineDecoded) 
fig.show()

来源

2017-04-19 07:19:12 matusko

谢谢 - 我在Jupyter Notebook中试过了你的方法，并且抛出了'matplotlib当前正在使用非GUI后端'的错误。我尝试用以下代码更改后端：'import matplotlib' 'matplotlib.use（'TkAgg'）' 'import matplotlib.pyplot as plt'但它引发错误'UserWarning：This call to matplotlib.use ）没有效果，因为后端已经被选中了。我需要抛弃Jupyter来让你的方法起作用吗？ – AggroCrag

根据初始化Jupyter Notebook的方式，matplotlib后端可能已经设置好了。如果是这种情况，尝试再次设置会导致此错误。这次对话虽然是Spyder，但描述了Jupyter笔记本电脑正在发生的事情。 https://groups.google.com/forum/#!topic/spyderlib/tRwgqEAIyvs –

是的，我想我无法更改Jupyter上的后端...我会坚持使用PyQtGraph。谢谢 – AggroCrag

随着你的字符串的复制/粘贴：

In [341]: astring="""137,136,151,145,141,133,145,139,140,145,144,139,143,141,139 
    ...: ,136,137,138,137,127,142,135,136,137,134,140,127,141,134,128,139,135,1 
    ...: 36,180,149,147,147,151,156,140,153,143,143,155,163,164,192,250,277,282 
    ...: ... 
,147,159,161,159,169,173,168,158,161,159,158,171,167,167,155,159,169,1 
    ...: 56,159,162,157,165,161,158,147,161,171,159"""

split(',')产生字符串列表。如果我换在np.array，我得到一个字符串数组：

In [342]: np.array(astring.split(',')) 
Out[342]: 
array(['137', '136', '151', '145', '141', '133', '145', '139', '140', 
     ... 
     '162', '157', '165', '161', '158', '147', '161', '171', '159'], 
     dtype='<U3')

我需要告诉它的字符串转换为整数：

In [343]: np.array(astring.split(','),int) 
Out[343]: 
array([137, 136, 151, 145, 141, 133, 145, 139, 140, 145, 144, 139, 143, 
     141, 139, 136, 137, 138, 137, 127, 142, 135, 136, 137, 134, 140, 
...., 165, 161, 158, 147, 161, 
     171, 159]) 
In [344]: _.shape 
Out[344]: (288,)

我第一次尝试它，字符串结束用逗号分隔："8,147,161,171,159,"。然后拆分包含一个空字符串，其中np.array不能转换为整数。我编辑了出来。我也可以从索引编号为[:-1]的字符串列表中删除它。

如果它能够将字符串列表（分割后）传递给绘图函数，那是因为该函数执行了相同类型的np.array(..., int)（或float）转换。

[int(i) for i in astring.split(',')]

可以用来创建一个整数列表。

来源

2017-04-19 07:40:42 hpaulj

感谢有关索引的信息。使用'[：-2]'允许我在最后修剪掉换行符和逗号。我用你的建议将字符串转换为整数（正如在对@E.Ducateme的回应中所提到的），但我仍然无法打开一个可用的Python窗口来显示PyQtGraph图并且不会崩溃。 – AggroCrag

'numpy'用户比'PyQtGraph'更有可能使用'matplotlib'进行绘图。你可能需要问一个单独的“PyQtGraph”问题，重点在于使该包能够工作。 – hpaulj

转换逗号分隔的字符串到numpy的阵列在Python 3

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