如何在 Pandas 数据框的列中添加空白单元格？

Question

I'm a beginner to Python and using dataframes thorugh Pandas. I'm trying to extract a table from an XML file using xml.dom.minidom into an Excel file. This is what the original table should look like (notice the black entry under 'Bike'):

VEHICLE   BRAND
Car       Mercedes
Bike      Kawasaki
          Ducati
Truck     Ram

I am trying to extract this table from the given XML file:

<Info_Collection>
    <Info car="Car">
        <V_Collection>
            <Brand type="Mercedes"/>
        </V_Collection>
    </Info>
    <Info car="Bike">
        <V_Collection>
            <Brand type="Kawasaki"/>
            <Brand type="Ducati"/>
        </V_Collection>
    </Info>
    <Info car="Truck">
        <V_Collection>
            <Brand type="Ram"/>
        </V_Collection>
    </Info>
</Info_Collection>

This is the code that I am using:

def main():
  x1=[]
  x2=[]
  doc = xml.dom.minidom.parse('xml_file')
  t1 = doc.getElementsByTagName("Info")
  t2 = doc.getElementsByTagName("Brand")
  for a in t1:
     x1.append(tb.getAttribute("car"))
  for a in t2:
     x2.append(tb.getAttribute("type"))
  while len(x1) != len(x2): 
     x1.append("")
  boDF = pd.DataFrame({'VEHICLE': x1, 'BRAND':x2})
  boDF.to_excel(writer, sheet_name='Sheet1', index=0, startrow=1)
  writer.save()

if __name__ == "__main__":
  main()

After running it, the output table is as follows:

VEHICLE   BRAND
Car       Mercedes
Bike      Kawasaki
Truck     Ducati
          Ram

Could someone kindly help me figure out how to insert a space between 'Bike' and 'Truck'? I tried to run both for loops concurrently and compared their lengths to see if they were equal or not and when they are not, a blank space would be added to the first column. However, I cannot get it to work. I know that the while loop in my code adds a space to the end of the first column, but I cannot figure out how to add anywhere inside the column.

Answer 1

See below.

The idea is to create a csv file which is usually associated with Excel. The XML parsing is done by builtin python XML parsing library 'ElementTree'. When you double click the csv file it will usually will be opened by Excel and you will get the table you are looking for.

Note that the XML you have posted is not a valid XML and had to be fixed (v_Collection Vs V_Collection)

import xml.etree.ElementTree as ET

xml = '''<Info_Collection>
    <Info car="Car">
        <V_Collection>
            <Brand type="Mercedes"/>
        </V_Collection>
    </Info>
    <Info car="Bike">
        <V_Collection>
            <Brand type="Kawasaki"/>
            <Brand type="Ducati"/>
        </V_Collection>
    </Info>
    <Info car="Truck">
        <V_Collection>
            <Brand type="Ram"/>
        </V_Collection>
    </Info>
</Info_Collection>'''

data = [['VEHICLE', 'BRAND']]
root = ET.fromstring(xml)
info_list = root.findall('.//Info')
cars = set()
for info_entry in info_list:
    car = info_entry.attrib['car']
    for brand in [brand.attrib['type'] for brand in info_entry.findall('.//Brand')]:
        data.append([car if car not in cars else '', brand])
        cars.add(car)
with open('cars.csv', 'w') as out:
    for entry in data:
        out.write(','.join(entry) + '\n')

output (cars.csv)

VEHICLE,BRAND
Car,Mercedes
Bike,Kawasaki
,Ducati
Truck,Ram