finding minimum and maximum element value from XML attributes using python

Question

I am trying to convert XML files into coco style json file. Here's how my XML file looks like

<Annotations MicronsPerPixel="0.466667">
<Annotation Id="1" Name="" ReadOnly="0" NameReadOnly="0" LineColorReadOnly="0" Incremental="0" Type="4" LineColor="65280" Visible="1" Selected="1" MarkupImagePath="" MacroName="">
    <Attributes/>
    <Regions>
        <RegionAttributeHeaders>
            <AttributeHeader Id="9999" Name="Region" ColumnWidth="-1"/>
            <AttributeHeader Id="9997" Name="Length" ColumnWidth="-1"/>
            <AttributeHeader Id="9996" Name="Area" ColumnWidth="-1"/>
            <AttributeHeader Id="9998" Name="Text" ColumnWidth="-1"/>
            <AttributeHeader Id="1" Name="Description" ColumnWidth="-1"/>
        </RegionAttributeHeaders>
        <Region Id="1" Type="0" Zoom="0.500000" Selected="0" ImageLocation="" ImageFocus="-1" Length="2243.6" Area="342402.0" LengthMicrons="1047.0" AreaMicrons="74567.5" Text="Benign" NegativeROA="0" InputRegionId="0" Analyze="1" DisplayId="1">
            <Attributes>
                <Attribute Name="1" Id="0" Value="Benign"/>
            </Attributes>
            <Vertices>
                <Vertex X="7398" Y="21614" Z="0"/>
                <Vertex X="7396" Y="21614" Z="0"/>
                <Vertex X="7392" Y="21636" Z="0"/>
                <Vertex X="7388" Y="21656" Z="0"/>
                <Vertex X="7386" Y="21660" Z="0"/>
                <Vertex X="7384" Y="21666" Z="0"/>
                <Vertex X="7384" Y="21670" Z="0"/>
                <Vertex X="7384" Y="21672" Z="0"/>
                <Vertex X="7384" Y="21674" Z="0"/>
                <Vertex X="7382" Y="21674" Z="0"/>
                <Vertex X="7382" Y="21676" Z="0"/>
                <Vertex X="7382" Y="21678" Z="0"/>
                <Vertex X="7382" Y="21680" Z="0"/>
                <Vertex X="7382" Y="21682" Z="0"/>
                <Vertex X="7380" Y="21682" Z="0"/>
                <Vertex X="7380" Y="21684" Z="0"/>
                <Vertex X="7380" Y="21686" Z="0"/>
                <Vertex X="7380" Y="21688" Z="0"/>
                <Vertex X="7380" Y="21690" Z="0"/>
                <Vertex X="7378" Y="21690" Z="0"/>
                <Vertex X="7378" Y="21694" Z="0"/>
                <Vertex X="7378" Y="21696" Z="0"/>
         </Vertices>
      </Region
  </Regions>
  <Plots/>
  </Annotation>

From this file I have to extract minimum and maximum X and Y vertex.

I am a beginner in python as well as parsing xml files for the first time

I tried below code to extract the minimum x

        xml_file = os.path.join(xml_path, f)
    print(xml_file)

    tree = ET.parse(xml_file)
    root = tree.getroot()


    #doc = etree.parse(filename)

    for elem in root:
        #print(elem,'-1')
        for child in elem:
            #print(child,'-2')
            if child.tag=='Regions':
                for gchild in child:
                    if gchild.tag=='Region':
                        id=gchild.get('Id')
                        print(id)
                        for subelem in gchild:
                            current_sub=subelem.tag
                            print(current_sub,'-4')
                            if current_sub=='Vertices':
                                for vertex in subelem:
                                    minx=100000
                                    for v in vertex.tag:
                                        x=int(vertex.get('X'))
                                        if x<minx:
                                            minx=x
                                        else:
                                            continue
                                    print(minx)

But, I am not getting the desired results. Is there a shorter and cleaner way to do this in python. With this code I am getting all the X coordinates as my output for minx

Similarly I have to get values for max_x , min_y and max_x to create a bounding box.

Answer 1

arrX, arrY = [], []
for vertex in root.findall('Vertex'):
    arrX.append(int(vertex.get('X')))
    arrY.append(int(vertex.get('Y')))
minX, maxX = min(arrX), max(arrX)
minY, maxY = min(arrY), max(arrY)

This should work if you don't have namespace in your XML.