Python coding for xml

I have a xml table with 2 columns Image-Pull-CMD and Image-size as below:

<table sorttable='yes'>
<tr>
<td value='Image-Pull-CMD' bgcolor='black' fontcolor='#fffff' fontattribute='bold' align='center' width='2000' />
<td value='Image-Size' bgcolor='black' fontcolor='#fffff' fontattribute='bold' align='center' width='1000' />
</tr>

<tr>
<td value='string1' bgcolor='white' fontcolor='black' fontattribute='bold' align='left' width='2000' />
<td value='1.16GB' bgcolor='white' fontcolor='black' fontattribute='normal' align='left' width='1000' />
</tr>

<tr>
<td value='string2' bgcolor='white' fontcolor='black' fontattribute='bold' align='left' width='2000' />
<td value='1.03GB' bgcolor='white' fontcolor='black' fontattribute='normal' align='left' width='1000' />
</tr>

<tr>
<td value='string3' bgcolor='white' fontcolor='black' fontattribute='bold' align='left' width='2000' />
<td value='2.55GB' bgcolor='white' fontcolor='black' fontattribute='normal' align='left' width='1000' />
</tr>

<tr>
<td value='string4' bgcolor='white' fontcolor='black' fontattribute='bold' align='left' width='2000' />
<td value='759MB' bgcolor='white' fontcolor='black' fontattribute='normal' align='left' width='1000' />
</tr>

<tr>
<td value='string5' bgcolor='white' fontcolor='black' fontattribute='bold' align='left' width='2000' />
<td value='500MB' bgcolor='white' fontcolor='black' fontattribute='normal' align='left' width='1000' />
</tr>
</table>
How can I sort the table by image size using python?