Unable to use python Pass External Parameter to Title in QMD via quarto render

[hasibagen]

下面是一个符合 Quarto 官方 Bug Report 指南的英文问题提问模板，基于你原来的问题和你提供的信息（Python 3.9、VSCode、Jupyter 环境）重写而成：

---

Title: External parameter not passed to title/subtitle when rendering to DOCX using Quarto

🐛 Bug Report

Summary

I’m trying to pass external parameters to dynamically generate the document title and subtitle in a .qmd file when rendering to Word (docx). However, the title and subtitle fields do not reflect the externally passed parameters—they always show the default values defined in the YAML.

---

🔁 Minimal, self-contained, reproducible example

---
title: "{{< meta params.mytitle >}}"
subtitle: "{{< meta params.mysubtitle >}}"
format:
  docx:
    reference-doc: word_temp.docx
    default-image-extension: svg
params:
  datapath: null
  mytitle: "Default Title"
  mysubtitle: "Default Subtitle"
engine: jupyter
jupyter: python3
---

```{python}
#| tags: [parameters]
# Placeholder for data path usage
print("Data path:", datapath)
```

Command used to render:

quarto render rest_rep_v1.qmd \
  -P datapath:"/some/path" \
  -P mytitle:"Test Hospital" \
  -P mysubtitle:"fNIRS Report" \
  --no-cache

Expected:
The generated Word document title should be "Test Hospital" and the subtitle should be "fNIRS Report".

Actual:
The title remains "Default Title" and the subtitle is "Default Subtitle" in the rendered .docx.

---

---

💻 Environment

quarto check

quarto check
Quarto 1.6.42
[✓] Checking environment information...
      Quarto cache location: /Users/jade/Library/Caches/quarto
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.4.0: OK
      Dart Sass version 1.70.0: OK
      Deno version 1.46.3: OK
      Typst version 0.11.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.6.42
      Path: /Applications/quarto/bin

[✓] Checking tools....................OK
      TinyTeX: (not installed)
      Chromium: (not installed)

[✓] Checking LaTeX....................OK
      Tex:  (not detected)

[✓] Checking basic markdown render....OK

[✓] Checking Python 3 installation....OK
      Version: 3.12.7 (Conda)
      Path: /Volumes/mind/opt/anaconda3/bin/python
      Jupyter: 5.7.2
      Kernels: python3

[✓] Checking Jupyter engine render....OK

[✓] Checking R installation...........OK
      Version: 4.4.2
      Path: /Library/Frameworks/R.framework/Resources
      LibPaths:
        - /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library
      knitr: 1.49
      rmarkdown: 2.29

[✓] Checking Knitr engine render......OK

---

📌 Question

Is there a recommended way to pass title and subtitle dynamically via -P when generating Word documents?
I’ve looked through related GitHub issues and documentation, but haven’t found a conclusive solution.

Any suggestions are greatly appreciated!

I came across a couple of related issues that seem to suggest parameter substitution may not work reliably inside the title or subtitle fields:

#8987

#10208

From those discussions, it seems that the title field might not fully support dynamic variable substitution (such as {{< meta ... >}} or {{params.xxx}}) in all formats or contexts. Could this be the root cause of the issue I'm experiencing?

---

[hasibagen]

Thanks for the discussion. I found that the following approach seems to work:

---
title: "{{< env MY_TITLE >}}"
subtitle: "{{< env MY_SUBTITLE >}}"
format:
  docx:
    reference-doc: word_temp.docx
    default-image-extension: svg
params:
  datapath: null
# ... other settings ...
---

And I render the document with:

MY_TITLE="test title" MY_SUBTITLE="try subtitle" quarto render /rest_rep_v1.qmd \
  -P datapath:"{file_path}" \
  --no-cache

This successfully injects the dynamic title and subtitle via environment variables.

However, I’m not sure whether relying on environment variables is the best practice, especially for reproducibility and clarity. Personally, I’d prefer a parameter-based solution (i.e., using -P mytitle:"..." instead of modifying the environment).

I've already reviewed all GitHub issues and discussions related to title and parameter usage, but haven't found a definitive answer for docx rendering with dynamic titles.

Does anyone have a recommended or more idiomatic way to achieve this?
Thanks in advance for any suggestions!

[mcanouil]

quarto render index.qmd --metadata title:"my title" should also work, but be aware that title is one of the structural option and is not a standard metadata as it is used in many parts.
You should not try to dynamically modify the title when in a Quarto project (book, website, etc.).

Side effects should be limited in single document project.

You can see in the "metadata" block at render time that it does not show your modified title.

[hasibagen]

quarto render index.qmd --metadata title:"my title" should also work, but be aware that title is one of the structural option and is not a standard metadata as it is used in many parts. You should not try to dynamically modify the title when in a Quarto project (book, website, etc.).

Side effects should be limited in single document project.

You can see in the "metadata" block at render time that it does not show your modified title.

This works perfectly—thank you so much for your reply and help!

For anyone who might have a similar use case, here’s my more advanced parameter-passing setup using Python:

command = (
    f'quarto render test.qmd '
    f'--to docx '
    f'-P datapath:"{file_path}" '
    f'--output {output_file} '
    f'--metadata title:"test" '
    f'--metadata subtitle:"try" '
    f'--no-cache'
)