Parsing XML Documents with ElementTree

From Repeated XML to Python Data

XML often contains several elements with the same structure, such as multiple user, product, or record elements. The practical task is usually to process every matching element rather than extract only one. ElementTree's findall method supports this pattern by locating all XML nodes that match a path and returning them as a Python list.

What findall Returns

Suppose a parsed XML tree has a users container with two user elements. Calling findall with the path for user elements does not return one user element. It returns a Python list containing two Element objects. Each Element represents one matching user subtree. This distinction matters: the result is a collection, while each item inside the collection is an individual XML node.

lst = root.findall("users/user")

Tracing the Loop Variable

A for loop processes the list sequentially. On each iteration, the loop variable is bound to the current Element object. With two matching user elements, the loop body runs twice: first with the Element for Chuck, whose id is 001 and whose x attribute is 2, and then with the Element for Brent, whose id is 009 and whose x attribute is 7. The loop stops automatically after all items have been processed.

for item in lst:
    name = item.find("name").text
    x_value = item.get("x")
    print(name, x_value)

Chuck 2
Brent 7

Reading Child Text and Attributes

An XML element can hold text between its opening and closing tags, and it can also have attributes on its opening tag. These are accessed differently. To read child-element text, first use find with the child name and then access the resulting element's text property. For a user element, item.find("name").text retrieves Chuck or Brent. To read an attribute belonging directly to the current user element, use item.get("x").

Debugging the Wrong Iteration Level

When iteration fails, first verify what findall returned before changing the loop body. Check the list length and inspect the first item. A length of zero means that the path or the expected XML structure does not match. If the length is correct but extraction fails inside the loop, inspect each item and check that the child-element and attribute names match exactly. XML names are case-sensitive.

print(len(lst)) print(lst[0]) for item in lst: print(item.find("name").text) print(item.get("x"))

• Treating the result of findall as one XML Element.

  findall returns a Python list, while the loop variable holds an individual Element.

  Fix: Iterate with for item in lst and call find or get on item.

• Ignoring an empty findall result.

  A list length of zero indicates that the path or expected XML structure did not match.

  Fix: Check the path and the XML structure, then inspect the returned list.

• Using the wrong child or attribute name.

  XML is case-sensitive, so names must match exactly.

  Fix: Compare the names in the extraction expressions with the XML names.

Practice the Extraction Pattern

The Complete Mental Model

1. findall searches a parsed XML tree and returns a Python list of matching Element objects.
2. The list is the collection; the for-loop variable is one individual Element during each iteration.
3. Use item.find(child_name).text to retrieve text from a child element.
4. Use item.get(attribute_name) to retrieve an attribute from the current Element.
5. When something fails, check the list length, inspect the first item, and verify XML names exactly.