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Interpolate %[meta-text] with %[sigils].

Project description

“An inscribed or painted symbol considered to have magical power.”

Sigils is a Python library for text and meta-text interpolation. It provides advanced capabilities such as context-based interpolation, function execution, nested and recursive interpolation, case-insensitive matching, and global context support.

Any Python object can be provided as context, including nested dictionaries, lists, and functions. Sigils can be used directly from Python or from the command line. Sigils is thread-safe and has no dependencies outside of the Python standard library.


Install Sigils using pip:

pip install sigils


Here’s a simple example of using Sigils:

from sigils import Sigil

context = {"user": {"name": "Alice"}}
s = Sigil("Hello, %[]!")
print(s % context)  # Outputs: Hello, Alice!

Sigils can handle function execution and nested interpolation:

from sigils import Sigil

context = {
    "user": {
        "name": "Alice",
        "greet": lambda name: f"Hello, {name}!"

s = Sigil("%[]")
print(s % context)  # Outputs: Hello, Alice!

s = Sigil("%[]")
print(s % context)  # Outputs: Hello,! is treated as a literal value

Sigils support case-insensitive matching and global context fallback:

from sigils import Sigil, Sigil.Context

global_context = {"greeting": "Hello, world!"}
with Sigil.Context(global_context):
    s = Sigil("%[GREETING]")
    print(s % {})  # Outputs: Hello, world!

Command-Line Usage

Sigils can be used directly from the command line. Here’s an example:

sigils "Hello, %[]!" -c context.json

In this example, “context.json” is a JSON file with a structure like {“user”: {“name”: “Alice”}}. The command will output: “Hello, Alice!”.


  • Function Execution: If the value of a Sigil is a callable function, it will be executed and its return value used in the string. Ensure all function values in your context are safe to execute.

  • Recursion Depth: Sigils handles up to 6 levels of nested interpolation by default. Adjust this limit by passing a different max_depth value to the interpolate method.

  • Thread Safety: The global context in Sigils is thread-safe. However, if you’re using mutable objects in your context and modifying them from multiple threads, manage thread safety at the application level.

  • Case-Insensitive Matching: If a key fails to resolve, a case-insensitive lookup is attempted. This only works if the keys in your context are all unique when lowercased.


Sigils is designed with performance in mind. In typical use cases, Sigils performs competitively with Python’s built-in string formatting.


Sigils is licensed under the MIT License. See the LICENSE file for details.

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