Python loop with lists

Question

I was writing some Python 3.2 code and this question came to me:

I've got these variables:

# a list of xml.dom nodes (this is just an example!)
child_nodes = [node1, node2, node3]
# I want to add every item in child_node into this node (this also a xml.dom Node)
parent = xml_document.createElement('TheParentNode')

This is exactly what I want to do:

for node in child_nodes:
    if node is not None:
        parent.appendChild(node)

I wrote it in one line like this:

[parent.appendChild(c) for c in child_nodes if c is not None]

I'm not going to use the list result at all, I only need the appendChild to do its work.

I'm not a very experienced python programmer, so I wonder which one is better? I like the single line solution, but I would like to know from experienced python programmers:

Which one is better, in a context of either code beauty/maintainability) and performance/memory use.

johnsyweb · Accepted Answer · 2011-06-11 22:36:38Z

8

The former is preferable in this situation.

The latter is called a list comprehension and creates a new list object full of the results of each call to parent.appendChild(c). And then discards it.

However, if you want to make a list based on this kind of iteration, then you should certainly employ a list comprehension.

edited Jun 11, 2011 at 22:36

answered Jun 11, 2011 at 22:31

johnsyweb

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Comments

Alex Bliskovsky · Accepted Answer · 2011-06-11 22:31:36Z

0

The question of code beauty/maintainability is a tricky one. It's really up to you and whoever you work with to decide.

For a long time I was uncomfortable with list comprehensions and so on and preferred writing it the first way because it was easier for me to read. Some people I work with, however, prefer the second method.

answered Jun 11, 2011 at 22:31

Alex Bliskovsky

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1 Comment

Ignacio Vazquez-Abrams Over a year ago

Not if it only uses the side effects.

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