8.2. Accessing the list of child elements

In many ways, an Element instance acts like a Python list, with its XML child elements acting as the members of that list.

You can use the Python len() function to determine how many children an element has. For example, if node is an Element instance with five element children, len(node) will return the value 5.

You can add, replace, or delete children of an element using regular Python list operations. For example, if an Element instance node has three child elements, node[0] is the first child, and node[2] is the third child.

In the examples that follow, assume that E is an Element instance.

E[i] returns the child element of E at position i, if there is one. If there is no child element at that position, this operation raises an IndexError exception.
E[i:j] returns a list of the child elements between positions i and j.
For example, node[2:4] returns a list containing the third and fourth children of node.
You can replace one child of an element E with a new element c using a statement of this form:
```
E[i] = c
```
If i is not the position of an existing child, this operation will raise an IndexError.
You can replace a sequence of adjacent children of an element E using slice assignment:
```
E[i:j] = seq
```
where seq is a sequence of Element instances.
If the slice [i:j] does not specify an existing set of children, this operation will raise an IndexError exception.
You can delete one child of an element like this:
```
del E[i]
```
where i is the index of that child.
You can delete a slice out of the list of element children like this:
```
del E[i:j]
```
You can iterate over the children of an element with a for loop. For example, if node is an Element instance, this code would print the tags of all its children:
```
for kid in node:
    print kid.tag
```

Not all children of an element are themselves elements.

Processing instructions are instances of class etree._ProcessingInstruction.
Comments are instances of class etree._Comment.

If you need to test whether a given child node is a processing instruuction or a comment, you can use Python's built-in function isinstance(I, C), which tests whether an object I is an instance of a class or subclass of class C.

For instance, to test whether node is a comment, you can use this test, which returns True if node is a comment, False otherwise.

issubclass(node, etree._Comment)

Python XML processing with lxml

8.2. Accessing the list of child elements

Python XML processing with `lxml`