How to edit Microsoft Word documents in Python

In preparation for the job market, I started polishing my CV. I try to keep the CV on my website as up-to-date as possible, but many recruiters and companies prefer a single-page neat CV in a Microsoft Word document. I used to always make my CV’s in LaTeX, but it seems Word is often preferred since it’s easier to edit for third parties.

Keeping both a web, Word, and PDF version all up-to-date and easy to edit seemed like an annoying task. I have plenty experience with automatically generating PDF documents using LaTeX and Python, so I figured why should a Word document be any different? Let’s dive into the world of editing Word documents in Python!

Fortunately there is a library for this: python-docx. It can be used to create Word documents from scratch, but stylizing a document is a bit tricky. Instead, its real power lies in editing pre-made documents. I went ahead and made a nice looking CV in Word, and now let’s open this document in python-docx. A Word document is stored in XML under the hoods, and there can be a complicated tree structure to a document. However, we can create a document and use the .paragraphs attribute for a complete list of all the paragraphs in the document. Let’s take a paragraph, and print it’s text content.

from docx import Document

document = Document("resume.docx")
paragraph = document.paragraphs[0]
print(paragraph.text)
Rik Voorhaar

Turns out the first paragraph contains my name! Editing this text is very easy; we just need to set a new value to the .text attribute. Let’s do this and safe the document.

paragraph.text = "Willem Hendrik"
document.save("resume_edited.docx")

Below is a picture of the resulting change; it unfortunately seems like two additional things happened when editing this paragraph: the font of the edited paragraph changed, and the bar / text box on the right-hand side disappeared completely!

img

This is no good, but to understand what happened to the text box we need to dig into the XML of the document. We can turn the document into an XML file like so:

document = Document("resume.docx")
with open('resume.xml', 'w') as f:
	f.write(document._element.xml)

It seems the problem was that the text box on the right was nested inside an other object, which is apparently not handled properly. This issue was easy to fix by modifying the Word document. However, the right bar on the side consists of 2 text boxes, and the top box with my contact information does disappear if I change the first paragraph. But, it does not disappear if I change the second paragraph; it only happens if I change paragraph 1 or 3 (and the latter is empty). I tried inserting two paragraphs before this particular paragraph, or changing the style of this particular paragraph, but the issue remains.

Looking at the XML the issue is clear: the text box element lies nested inside this paragraph! It turned out to be a bit tricky to avoid this, so for now let us then try changing the second paragraph, changing the word “resume” for “curriculum vitae”.

document = Document("resume.docx")
paragraph = document.paragraphs[1]
print(paragraph.text)
paragraph.text = "Curriculum Vitae"
document.save("CV.docx")
Resume

If we do this there’s no problems with text boxes disappearing, but unfortunately the style of this paragraph is still reset when we do this. Let’s have a look at how the XML changes when we edit this paragraph. Ignoring irrelevant information, before changing it looks like this:

<w:p>
    <w:r>
    <w:t>R</w:t>
    </w:r>
    <w:r>
    <w:t>esume</w:t>
    </w:r>
</w:p>

And afterwards it looks like this:

<w:p>
    <w:r>
    <w:t>Curriculum Vitae</w:t>
    </w:r>
</w:p>

In Word, each paragraph (<p>) is split up in multiple runs (<r>). What we see here is that originally the paragraph was two runs, and after modifying it, it became a single run. However, it seems that in both cases the style information is exactly the same, so I don’t understand why the style changes after modification. In this case if I retype the word ‘Resume’ in the original word document, this paragraph become a single run, but still the style changes after editing, and I still don’t see why this happens when looking at the XML.

Looking at the source code of python-docx I noticed that when we call paragraph.text = ..., what happens is that the contents of the paragraph get deleted, and then a new run is added with the desired text. It is not clear to me at where exactly the style information is stored, but either way there is a simple workaround to what we’re trying to do: we can simply modify the text of the first run in the paragraph, rather than clearing the entire paragraph and adding a new one. This in fact also works for editing the first paragraph, where before we had problems with disappearing text boxes:

document = Document("resume.docx")
with open('resume.xml', 'w') as f:
	f.write(document._element.xml)

# Change 'Rik Voorhaar' for 'Willem Hendrik Voorhaar'
paragraph = document.paragraphs[0]
run = paragraph.runs[1]
run.text = 'Willem Hendrik Voorhaar'

# Change 'Resume' for 'Curriculum Vitae'
paragraph = document.paragraphs[1]
run = paragraph.runs[0]
run.text = 'Curriculum Vitae'
document.save('CV.docx')

Doing this changes the text, but leaves all the style information the same. Alright, now we now how to edit text. It’s more tricky than one might expect, but it does work!

Dealing with text boxes

Let’s say that next we want to edit the text box on the right-hand side of the document, and add a skill to our list of skills. We’ve been diving into the inner workings of Word documents, so it’s fair to say we know how to use Microsoft Word, so let’s add the skill “Microsoft Word” to the list.

To do this we first want to figure out in which paragraph this information is stored. We can do this by going through all the paragraphs in the document and looking for the text “Skills”.

import re
pattern = re.compile("Skills")
for p in document.paragraphs:
    if pattern.search(p.text):
        print("Found the paragraph!")
        break
else:
    print("Did not find the paragraph :(")
Did not find the paragraph :(

Seems like there is unfortunately no matching paragraph! This is because the paragraph we want is inside a text box, and modifying text boxes is not supported in python-docx. This is a known issue, but instead of giving up I decided to add support for modifying text boxes to python-docx myself! It turned out not to be too difficult to implement, despite my limited knowledge of both the package and the inner structure of Word documents.

The first step is understanding how text boxes are encoded in the XML. It turns out that the structure is something like this:

<mc:AlternateContent>
    <mc:Choice Requires="wps">
        <w:drawing>
            <wp:anchor>
                <a:graphics>
                    <a:graphicData>
                        <wps:txbx>
                            <w:txbxContent>
                            ...
                            <w:txbxContent>
                        </wps:txbx>
                    </a:graphicData>                 
                </a:graphics>
            </wp:anchor>
        </w:drawing>
    </mc:Choice>
    <mc:Fallback>
        <w:pict>
            <v:textbox>
                <w:txbxContent>
                ...
                <w:txbxContent>
            </v:textbox>
        </w:pict>
    </mc:Fallback>
</mc:AlternateContent>

The insides of the two <w:txbxContent> elements are exactly identical. The information is stored twice probably for legacy reasons. A quick Google reveals that wps is an XML namespace introduced in Office 2010, and WPS is short for Word Processing Shape. The textbox is therefore stored twice to maintain backwards compatibility with older Word versions. Not sure many people still use Office 2006… Either way, this means that if we want to update the contents of the textbox, we need to do it in two places.

Next we need to figure out how to manipulate these word objects. My idea is to create a TextBox class, that is associated to an <mc:AlternateContent> element, and which ensures that both <w:txbxContent> elements are always updated at the same time. First we make a class encoding a <w:txbxContent> element. For this we can build on the BlockItemContainer class already implemented in python-docx. Mixing in this class gives automatic support for manipulating paragraphs inside of the container.

class TextBoxContent(BlockItemContainer)

Given an <mc:AlternateContent> object, we can access the two <w:txbxContent> elements using the following XPath specifications:

XPATH_CHOICE = "./mc:Choice/w:drawing/wp:anchor/a:graphic/a:graphicData//wps:txbx/w:txbxContent"
XPATH_FALLBACK = "./mc:Fallback/w:pict//v:textbox/w:txbxContent"

Then making a rudimentary TextBox class is very simple. We base it on the ElementProxy class in python-docx. This class is meant for storing and manipulating the children of an XML element.

class TextBox(ElementProxy):
        """Implements texboxes. Requires an `<mc:AlternateContent>` element."""

    def __init__(self, element, parent):
        super(TextBox, self).__init__(element, parent)

        try:
            (tbox1,) = element.xpath(XPATH_CHOICE)
            (tbox2,) = element.xpath(XPATH_FALLBACK)
        except ValueError as err:
            raise ValueError(
                "This element is not a text box; it should contain precisely two \
                    ``<w:txbxContent>`` objects"
            )
        self.tbox1 = TextBoxContent(tbox1, self)
        self.tbox2 = TextBoxContent(tbox2, self)

So far this is just good for storing the text box, we still need some code to actually manipulate it. It would also be great if we have a way to find all the text boxes in a document. This is as simple as finding all the <mc:AlternateContent> elements with precisely two <w:txbxContent> elements. We can use the following function:

def find_textboxes(element, parent):
    """
    List all text box objects in the document.

    Looks for all ``<mc:AlternateContent>`` elements, and selects those
    which contain a text box. 
    """
    alt_cont_elems = element.xpath(".//mc:AlternateContent")
    text_boxes = []
    for elem in alt_cont_elems:
        tbox1 = elem.xpath(XPATH_CHOICE)
        tbox2 = elem.xpath(XPATH_FALLBACK)
        if len(tbox1) == 1 and len(tbox2) == 1:
            text_boxes.append(TextBox(elem, parent))
    return text_boxes

We then update the Document class with a new textboxes attribute:

@property
def textboxes(self):
    """
    List all text box objects in the document.
    """
    return find_textboxes(self._element, self)

Now let’s test this out:

document = Document("resume.docx")
document.textboxes
[<docx.oxml.textbox.TextBox at 0x7faf395c3bc0>,
 <docx.oxml.textbox.TextBox at 0x7faf395c3100>]

Now to manipulate the “Skills” section as we initially wanted, we first find the right paragraph. Since the two <w:txbxContent> objects have the same paragraphs, we need to find which number of paragraph contains the text, and in which textbox:

import re
def find_paragraph(pattern):
    for textbox in document.textboxes:  
        for i,p in enumerate(textbox.paragraphs):
            if pattern.search(p.text):
                return textbox,i
pattern = re.compile("Skills")
textbox, i = find_paragraph(pattern)
print(textbox.paragraphs[i].text)
Skills

Now to insert a new skill, we need to create a new paragraph with the text “Microsoft Word”. For this we can find the paragraph right after, and this paragraphs insert_paragraph_before method with appropriate text and style information. The paragraph in question is the one containing the word “Research”. I want to copy the style of this paragraph to the new paragraph, but for some reason the style information is empty for this paragraph. However, I know that the style of this paragraph should be the 'Skillsentries', so I can just use that directly.

style = document.styles['Skillsentries']

pattern = re.compile("Research")
textbox,i = find_paragraph(pattern)

p1 = textbox.tbox1.paragraphs[i]
p2 = textbox.tbox2.paragraphs[i]

for p in (p1,p2):
    p.insert_paragraph_before("Microsoft Word", p.style)
document.save("CV.docx")

When now opening the Word document, we see the item “Microsoft Word” in my list of skills, with the right style and everything. I did cheat a little; I needed to make some additional technical changes to the code for this all to work, but the details are not super important. If you want to use this feature, you can use my fork of python-docx. My solution is still a little hacky, so I don’t think it will be added to the main repository, but it does work fine for my purposes.

Conclusion

In summary, we can use Python to edit word documents. However the python-docx package is not fully mature, and using it for editing highly-stylized word documents is a bit painful (but possible!). It is however quite easy to extend with new functionality, in case you do need to do this. On the other hand, there is quite extensive functionality in Visual Basic to edit word documents, and the whole Word API is built around Visual Basic.

While I now have all the tools available to automatically update my CV using Python, I will actually refrain from doing it. It is a lot of work to set up properly, and needs active maintenance ever time I would want to change the styling of my CV. Probably it’s a better idea to just manually edit it every time I need to. Automatization isn’t always worth it. But I wouldn’t be surprised if this new found skill will be useful at some point in the future for me.

Recent posts

GMRES: or how to do fast linear algebra


24 minute read

Linear least-squares system pop up everywhere, and there are many fast way to solve them. We’ll be looking at one such way: GMRES.

Blind Deconvolution #2: Image Priors


15 minute read

In order to automatically sharpen images, we need to first understand how a computer can judge how ‘natural’ an image looks.