numpy 保存包含麻木数组的Pandas Dataframe

m4pnthwp  于 2022-11-10  发布在  其他
关注(0)|答案(4)|浏览(150)

我有一个 Dataframe ,其中一列充满了无用的数组。

A     B         C
0   1.0   0.000000  [[0. 1.],[0. 1.]]
1   2.0   0.000000  [[85. 1.],[52. 0.]]
2   3.0   0.000000  [[5. 1.],[0. 0.]]
3   1.0   3.333333  [[0. 1.],[41. 0.]]
4   2.0   3.333333  [[85. 1.],[0. 21.]]

问题是,当我将其另存为CSV文件时,并且当我将其加载到另一个Python文件中时,NumPy列被读取为文本。
我尝试使用np.fromstring()np.loadtxt()转换列,但不起作用。
pd.read_csv()后的AND数组示例

"[[ 85.  1.]\n [   52.            0.        ]]"

谢谢

ippsafx7

ippsafx71#

下面的代码应该可以工作。我用了另一个问题来解决它,里面有更多的解释:Convert a string with brackets to numpy array

import pandas as pd
import numpy as np

from ast import literal_eval

# Recreating DataFrame

data = np.array([0, 1, 0, 1, 85, 1, 52, 0, 5, 1, 0, 0, 0, 1, 41, 0, 85, 1, 0, 21], dtype='float')
data = data.reshape((5,2,2))

write_df = pd.DataFrame({'A': [1.0,2.0,3.0,1.0,2.0],
                   'B': [0,0,0,3+1/3,3+1/3],
                   'C': data.tolist()})

# Saving DataFrame to CSV

fpath = 'D:\\Data\\test.csv'
write_df.to_csv(fpath)

# Reading DataFrame from CSV

read_df = pd.read_csv(fpath)

# literal_eval converts the string to a list of tuples

# np.array can convert this list of tuples directly into an array

def makeArray(rawdata):
    string = literal_eval(rawdata)
    return np.array(string)

# Applying the function row-wise, there could be a more efficient way

read_df['C'] = read_df['C'].apply(lambda x: makeArray(x))
ryoqjall

ryoqjall2#

你可以试试.to_json()

output = pd.DataFrame([
  {'a':1,'b':np.arange(4)},
  {'a':2,'b':np.arange(5)}
]).to_json()

但当使用以下命令重新加载时,您将只会得到列表

df=pd.read_json()

使用以下命令将它们转换为麻木数组:

df['b']=[np.array(v) for v in df['b']]
o0lyfsai

o0lyfsai3#

这是一个丑陋的解决方案。

import pandas as pd
import numpy as np

### Create dataframe

a = [1.0, 2.0, 3.0, 1.0, 2.0]
b = [0.000000,0.000000,0.000000,3.333333,3.333333]
c = [np.array([[0. ,1.],[0. ,1.]]),
np.array([[85. ,1.2],[52. ,0.]]),
np.array([[5. ,1.],[0. ,0.]]),
np.array([[0. ,1.],[41. ,0.]]),
np.array([[85. ,1.],[0. ,21.]]),]

df = pd.DataFrame({"a":a,"b":b,"c":c})

#### Save to csv

df.to_csv("to_trash.csv")
df = pd.read_csv("to_trash.csv")

### Bad string manipulation that could be done better with regex

df["c"] = ("np.array("+(df
 .c
 .str.split()
 .str.join(' ')
 .str.replace(" ",",")
 .str.replace(",,",",")
 .str.replace("[,", "[", regex=False)
)+")").apply(lambda x: eval(x))
drnojrws

drnojrws4#

我找到的最好的解决方案是使用Pickle文件。
您可以将 Dataframe 保存为泡菜文件。

import pickle
img = cv2.imread('img1.jpg')
data = pd.DataFrame({'img':img})

data.to_pickle('dataset.pkl')

然后你就可以把它读成泡菜文件:

with (open(ref_path + 'dataset.pkl', "rb")) as openfile:
     df_file = pickle.load(openfile)

让我知道它是否起作用了。

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