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.
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 print(paragraph.text)
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
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!
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 print(paragraph.text) paragraph.text = "Curriculum Vitae" document.save("CV.docx")
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 run = paragraph.runs run.text = 'Willem Hendrik Voorhaar' # Change 'Resume' for 'Curriculum Vitae' paragraph = document.paragraphs run = paragraph.runs 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
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
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
TextBox class, that is associated to an
element, and which ensures that both
<w:txbxContent> elements are always
updated at the same time. First we make a class encoding a
element. For this we can build on the
BlockItemContainer class already
python-docx. Mixing in this class gives automatic support for
manipulating paragraphs inside of the container.
<mc:AlternateContent> object, we can access the two
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
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
@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)
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
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.
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
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