python - 使用 Pandas 将多行数据导出到 csv

Question

我有一个匹配算法，可以将学生与项目联系起来。它正在运行，但我无法将数据导出到 csv 文件。当有 200 个值要导出时，它仅采用最后一个值并仅导出该值。

当我想要获取整个“s”而不是组成“s”的三个 3 数字时，导出的数据使用每个数字作为值，它们被分成三列。我附上了下面的图片。任何帮助将不胜感激。

What it looks like

What it should look like

#Imports for Pandas

import pandas as pd
from pandas import DataFrame 

SPA()
for m in M:
   s = m['student']
   l = m['lecturer']
   Lecturer[l]['limit'] = Lecturer[l]['limit'] - 1
   id = m['projectid']
   p = Project[id]['title']
   c = Project[id]['sourceid']
   r = str(getRank("Single_Projects1copy.csv",s,c))


   print(s+","+l+","+p+","+c+","+r)

   dataPack = (s+","+l+","+p+","+c+","+r)

   df = pd.DataFrame.from_records([dataPack])
   df.to_csv('try.csv')

Answer 1

你在循环中不断覆盖，所以你只得到最后一位数据，你需要用 df.to_csv('try.csv',mode="a",header= False) 或创建一个 df 并附加到它并在循环外写入，例如:

df = pd.DataFrame()
for m in M:
   s = m['student']
   l = m['lecturer']
   Lecturer[l]['limit'] = Lecturer[l]['limit'] - 1
   id = m['projectid']
   p = Project[id]['title']
   c = Project[id]['sourceid']
   r = str(getRank("Single_Projects1copy.csv",s,c))


   print(s+","+l+","+p+","+c+","+r)

   dataPack = (s+","+l+","+p+","+c+","+r)

   df.append(pd.DataFrame.from_records([dataPack]))
df.to_csv('try.csv') # write all data once outside the loop

更好的选择是打开一个文件并将该文件对象传递给 to_csv:

with open('try.csv', 'w') as f:
    for m in M:
       s = m['student']
       l = m['lecturer']
       Lecturer[l]['limit'] = Lecturer[l]['limit'] - 1
       id = m['projectid']
       p = Project[id]['title']
       c = Project[id]['sourceid']
       r = str(getRank("Single_Projects1copy.csv",s,c))
       print(s+","+l+","+p+","+c+","+r)

       dataPack = (s+","+l+","+p+","+c+","+r)
       pd.DataFrame.from_records([dataPack]).to_csv(f, header=False)

你得到单独的字符，因为你使用 from_records 传递一个字符串 dataPack 作为值，所以它遍历字符:

In [18]: df = pd.DataFrame.from_records(["foobar,"+"bar"])

In [19]: df
Out[19]: 
   0  1  2  3  4  5  6  7  8  9
0  f  o  o  b  a  r  ,  b  a  r

In [20]: df = pd.DataFrame(["foobar,"+"bar"])

In [21]: df
Out[21]: 
            0
0  foobar,bar

我认为您基本上希望作为元组 dataPack = (s, l, p,c, r) 并使用 pd.DataFrame(dataPack)。你根本不需要 pandas，csv 库会为你做这一切，而不需要创建数据帧。