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Create a Pattern

We are going to convert an existing project into a pattern. This process is going to require lots of search and replace.

In another tutorial, we will break it into several patterns.

Setup

  1. Create a new directory named patterns.
  2. Download the example project as a .zip file from TODO
  3. Decompress the file and copy the todo-manager project into patterns/.
  4. Inside the patterns/ directory, create a file named core_pattern.toml

Note

If you are doing this with an actual project, remove the .git directory if it exists.

Extracting questions

Questions are asked of the user during the project generation. Each answer is set as the value of a variable used in patterns. We will go through this example project and highlight information that would or could vary between projects. We will create questions to get the data from the user, and then we will replace the existing values in the example project with placeholders.

Different names in different places

The outer folder is named todo-manager, the code folder is named todo_manager, and the title of the README.md file is Todo Manager. Are these three different variables that require three different questions? Is this one variable with three permutations that only require one question?

We will treat them as three variables. However, we don’t necessarily require three answers.

Project name

Let’s start with the title of the README.md file. We’ll call this the project_name. We want to use this wherever we need a human-friendly name. Add a question to core_pattern.toml

patterns/core_pattern.toml
[[questions]]
name = "project_name"
prompt = "What is the human-friendly name of the project?"
type = "str"
default = "My Project"

Package name

Now, let’s deal with the outer folder name and the code folder. Python package names (the package name registered with the Python package index) are normalized using hyphens. However, hyphens are not allowed in Python identifiers.

We’ll call the name of the code folder the package_name. Add this question to core_pattern.toml:

patterns/core_pattern.toml
# ... previous question

[[questions]]
name = "package_name"
promp = "What is the name of the Python package?"
type = "str"
default = "{{ project_name|lower|replace(' ', '_') }}"

This sets the default answer to a modification of the previous question’s answer. It converts the answer to lowercase and replaces all spaces with underscores. This is likely what the user wants, and if so, they can accept the default without having to type anything.

Repo name

We’ll call the name of the outer folder the repo_name. Add this question to core_pattern.toml:

patterns/core_pattern.toml
# ... previous questions

[[questions]]
name = "repo_name"
prompt = "What is the name of the project repository?"
type = "str"
default = "{{ package_name|replace('_', '-') }}"

This question modifies the answer from package_name, replacing the underscores with hyphens.

Set the placeholders in files

  • Search for Todo Manager and replace it with {{ project_name }}
  • Search for todo_manager and replace it with {{ package_name }}
  • Search for todo-manager and replace it with {{ repo_name }}

Renaming files and directories with placeholders

  • Rename the todo-manager directory to {{ repo_name }}
  • Rename the todo_manager directory to {{ package_name }}

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