如何通过 python 将列表数据添加到 CSV 文件的第一列，该文件有 256 列文件？

Question

I have a CSV file which has 255 columns and 16,000 rows of data, and I want to add a list of data which contains 16,000 data to the first column of my CSV file.

The code I tried to use is

# Append the name of the file to List
path = 'C:/Users/User/Desktop/Guanlin_CNN1D/CNN1D/0.3 15 and 105 circle cropped'
list = os.listdir(path)
List = []
for a in list:
    List.append(str(a))   

## Load the to-be-added CSV file
data = pd.read_csv('C:/Users/User/Desktop/Guanlin_CNN1D/CNN1D/0.3 15 and 105 for toolpath recreatation.csv',sep=',', engine='python' ,header=None)
tempdata = pd.DataFrame(data)
features = tempdata.values[:, 1:]
file_num = tempdata.values[:, 0]

# add the List to first columns of CSV file
Temp = {List,file_num,features}
temp = pd.DataFrame(Temp)
temp

The result shows

TypeError: unhashable type: 'list'

How to rewrite the code?

Thanks in advance!

Answer 1

I think you simply need to use the dataframe insert method. It looks like you are trying to create a new dataframe but I think it is not necessary. Below example inserts a new column at the zeroth position. It looks like you were trying to make a new dataframe from a dict; this link has some easy examples on way to populate a dataframe with lists and dicts. I think the number of rows and columns should not be a concern for you in this case.

import numpy as np
import pandas as pd

np.random.seed(0)

df = pd.DataFrame(np.random.randint(0, 100, size=(5, 5)), columns=list('ABCDE'))
print(df)

df.insert(0,column='newcol', value=np.random.randint(0, 100, size=(5)))
print()
print(df)

df.to_csv( r'data.csv', index=False, header=True)

will produce this output

    A   B   C   D   E
0  44  47  64  67  67
1   9  83  21  36  87
2  70  88  88  12  58
3  65  39  87  46  88
4  81  37  25  77  72

   newcol   A   B   C   D   E
0       9  44  47  64  67  67
1      20   9  83  21  36  87
2      80  70  88  88  12  58
3      69  65  39  87  46  88
4      79  81  37  25  77  72