Use a variable for an Xpath query in Python

Question

[N.B. I'm quite new to Python & Xpath]

I was wanting to perform an Xpath query and use a variable in the expression to cycle through all the elements using an index.

For example, rather than having the specific position of [1], [2], etc, I'd like to be able to place a variable i in this expression:

for x in root.xpath('/movies/a_movie[i]/studio'):
    print "<studio>" + x.text + "</studio>"

I'm unsure whether it's even possible, but I guess it can't hurt to ask!

To clarify, this is why I would like to do this: I'm trying to process all the elements of a_movie[1], then at the end of the function, I want to process all the elements of a_movie[2], and so on.

Just leave outh the [i] altogether? You are selecting studio elements that are inside of a a_movie element, you already would be looping over all matches.. — Martijn Pieters
– Martijn Pieters, Commented Mar 28, 2013 at 11:15
@MartijnPieters I had that originally, but it didn't fit my needs – I'm trying to process all the elements of a_movie[1], then at the end of the function, I wanted to process all the elements of a_movie[2]. — Daniel
– Daniel, Commented Mar 28, 2013 at 11:19

Martijn Pieters · Accepted Answer · 2013-03-28 12:16:32Z

1

You want to loop over the /movies/a_movie tags instead, but only those that have a studio child:

for a_movie in root.xpath('/movies/a_movie[studio]'):
    name = a_movie.find('name').text
    studio = a_movie.find('studio')
    print "<studio>" + studio.text + "</studio>"

If you wanted to just print out the child elements of the a_movie element as XML, I'd just loop over the element (looping over the child elements) and use ElementTree.tostring() on each:

for a_movie in root.xpath('/movies/a_movie'):
    for elem in a_movie:
        print ElementTree.tostring(elem),

edited Mar 28, 2013 at 12:16

answered Mar 28, 2013 at 11:22

Martijn Pieters

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10 Comments

Daniel Over a year ago

Thanks, Martijn. However, this still results in the issue I mentioned before; when I run my script, it prints all the child names successively – e.g. it printed all the studio names of each of the a_movie elements in the XML file at once. I want it to print the children names of a_movie[1], then all the children names of a_movie[2], then a_movie[3]… The reason I'd like to do this is to use the same block of code to process each of the a_movie elements.

Martijn Pieters Over a year ago

@Daniel: This loops over the a_movie tags in order. If there are multiple <studio> tags inside each a_movie tag, then loop over those too. You didn't include a sample of your input XML, so I have to guess at what you mean here.

Daniel Over a year ago

Here is the input XML: cl.ly/code/2N3F1g3L2W0V I hope that helps clarify…

Martijn Pieters Over a year ago

@Daniel: What is the problem then? This code does what you want to do already. It loops over a_movie tags in order, then finds the studio tag inside. Inside the loop you are processing the a_movie tag. Added printing the movie name.

Daniel Over a year ago

You must be misunderstanding my intention – here is the desired output:

<title>The Lord of the Rings: The Fellowship of the Ring</title> <rating>PG</rating> <studio>New Line Cinema</studio> <genre>Fantasy</genre>

etcetera for each movie. In other words, I would like to reproduce the XML code how it currently appears.

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