Python: Extracting XML to DataFrame (Pandas)

Question

a have an XML file that looks like this:

<?xml version="1.0" encoding="utf-8"?>
<comments>
<row Id="1" PostId="2" Score="0" Text="(...)" CreationDate="2011-08-30T21:15:28.063" UserId="16" />
<row Id="2" PostId="17" Score="1" Text="(...)" CreationDate="2011-08-30T21:24:56.573" UserId="27" />
<row Id="3" PostId="26" Score="0" Text="(...)" UserId="9" />
</comments>

What I'm trying to do is to extract ID, Text and CreationDate colums into pandas DF and I've tryied following:

import xml.etree.cElementTree as et
import pandas as pd
path = '/.../...'
dfcols = ['ID', 'Text', 'CreationDate']
df_xml = pd.DataFrame(columns=dfcols)

root = et.parse(path)
rows = root.findall('.//row')
for row in rows:
    ID = row.find('Id')
    text = row.find('Text')
    date = row.find('CreationDate')
    print(ID, text, date)
    df_xml = df_xml.append(pd.Series([ID, text, date], index=dfcols), ignore_index=True)

print(df_xml)

But the output is: None None None

Could you please tell how to fix this? THanks

Answer 1

As advised in this solution by gold member Python/pandas/numpy guru, @unutbu:

Never call DataFrame.append or pd.concat inside a for-loop. It leads to quadratic copying.

Therefore, consider parsing your XML data into a separate list then pass list into the DataFrame constructor in one call outside of any loop. In fact, you can pass nested lists with list comprehension directly into the constructor:

path = 'AttributesXMLPandas.xml'
dfcols = ['ID', 'Text', 'CreationDate']

root = et.parse(path)
rows = root.findall('.//row')

# NESTED LIST
xml_data = [[row.get('Id'), row.get('Text'), row.get('CreationDate')] 
            for row in rows]

df_xml = pd.DataFrame(xml_data, columns=dfcols)

print(df_xml)

#   ID   Text             CreationDate
# 0  1  (...)  2011-08-30T21:15:28.063
# 1  2  (...)  2011-08-30T21:24:56.573
# 2  3  (...)                     None

Answer 2

Just a minor change in your code

ID = row.get('Id')
text = row.get('Text')
date = row.get('CreationDate')