Reset variable when using for loop in python

Question

I am a relatively new programmer, using xml element tree to iterate through an xml file of data on members. I am iterating through the members to extract data and allocate to variables for surname, firstname and id.

The problem I have is that if one of the members has a missing element (as opposed to missing data within an element), then my current code maintains the variable value from the last iteration (member).

My data:

<?xml version='1.0' ?>
<members>
    <member>
        <field name="surname">
            <text>Smith</text>
        </field>
        <field name="firstname" type="text">
            <text>John</text>
        </field>
        <field name="id" type="text">
            <text>123</text>
        </field>
    </member>
        <member>
        <field name="surname" type="text">
            <text>Bloggs</text>
        </field>

<!--missing firstname element here -->

        <field name="id" type="text">
            <text>789</text>
        </field>
    </member>
    <member>
        <field name="surname" type="text">
            <text>Jones</text>
        </field>
        <field name="firstname" type="text">
            <text>Jane</text>
        </field>
        <field name="id" type="text">
            <text>456</text>
        </field>
    </member>
</members>

My code:

tree = ET.parse('mydata.xml')
root = tree.getroot()
y = root.findall('member')
for member in y:
    fields = member.findall("field")
    for field in fields:
        if field.get('name') == 'surname':
            surname = field.find('text').text
        if field.get('name') == 'firstname':
            firstname = field.find('text').text
        if field.get('name') == 'id':
            id = field.find('text').text

    print(surname, firstname, id)    

Desired output:

Smith John 123
Bloggs  789
Jones Jane 456

Actual output, which shows Bloggs' firstname as John rather than blank:

Smith John 123
Bloggs John 789
Jones Jane 456

I can avoid this by setting the surname, firstname and id variable prior to each member iteration:

for member in y:
    surname = ''
    firstname = ''
    id = ''

    fields = member.findall("field")
    for field in fields:
        if field.get('name') == 'surname':
            surname = field.find('text').text
        if field.get('name') == 'firstname':
            firstname = field.find('text').text
        if field.get('name') == 'id':
            id = field.find('text').text

    print(surname, firstname, id)

which gives the desired result:

Smith John 123
Bloggs  789
Jones Jane 456

However this feels a bit of a workaround - is there an alternative, more pythonic way to achieve this?

Answer 1

What you have is actually quite OK and readable. But if you really want to you could use a ternary expression

for member in y:
    fields = member.findall("field")
    for field in fields:
        surname = field.find('text').text if field.get('name') == 'surname' else ''
        firstname = field.find('text').text if field.get('name') == 'firstname' else ''
        id = field.find('text').text if field.get('name') == 'id' else ''

    print(surname, firstname, id)

Answer 2

Maybe this is easier to achieve by putting the data into a dict using a dict comprehension. This way the dict will always be overwritten, even if it's completely empty because there are no fields in a member :

for member in root.findall("member"):
    data = {field.get("name") : field.find("text").text for field in member.findall("field")}
    print(
        data.get("surname", "(no surname"),
        data.get("firstname", "(no firstname)"),
        data.get("id", "(no id")
    )

=>

Smith John 123
Bloggs (no firstname) 789
Jones Jane 456

Answer 3

those things are maybe better isolated to an own function. and yes you should reset them first when you want empty fields