Alejandro Alcalde

Data Scientist and Computer Scientist. Creator of this blog.

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Recently I’ve updated my blog from jekyll to Hugo. The process was easy enough, but I did have to change some things in the frontmatter of the content.

A simple Google search was all I needed to find a python parser for YAML frontmatter. Here is how I did it:

Install Python-Frontmatter

Simply run

sudo pip install python-frontmatter

Using Python-Frontmatter

Example 1: Add new values to frontmatter

Once installed, it is easy to use. Let’s see as an example one of the problems I faced. In Jekyll I was the fall back author for all posts that did not have one defined in its frontmatter, but in Hugo I need to specify the author for every post written. To accomplish this, I wrote the following script:

import frontmatter
import io
from os.path import basename, splitext
import glob

# Where are the files to modify
path = "en/*.markdown"

# Loop through all files
for fname in glob.glob(path):
    with, 'r') as f:
        # Parse file's front matter
        post = frontmatter.load(f)
        if post.get('author') == None:
            post['author'] = "alex"
            # Save the modified file
            newfile =, 'w', encoding='utf8')
            frontmatter.dump(post, newfile)

That’s it!, so simple. Let’s see another example

Example 2: Modify existing values in frontmatter

In this case, I had two frontmatter variables, mainclass and categories. I wanted to include the value of mainclass into categories, and keep all the current categories of categories. Here is the script:

for fname in glob.glob(path):
    with, 'r') as f:
        post = frontmatter.load(f)

        # If no categories exists, create one with the value of mainclass
        if post.get('categories') == None:
            post['categories'] = [post['mainclass']]
        else: # Categories exists
            cat = post['categories']
            main = post['mainclass']
            # If categories contains a single item, ex: categories: 'category1'
            if type(cat) == str:
                if cat.lower() != main:
                    cat = [cat, main]
            else: # If categories is a list, ex: categories: [cat1, cat2]
                cat = [s.lower() for s in cat]
                if main in cat == False:

            post['categories'] = cat
            print("%s") % (post['categories'])

        # Save the file.
        newfile =, 'w', encoding='utf8')
        frontmatter.dump(post, newfile)


Spot a typo?: Help me fix it by contacting me or commenting below!


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