Interpolate with %[sigils].
Project description
“An inscribed or painted symbol considered to have magical power.”
Sigils is a Python library for magic and string 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.
Installation
Install Sigils using pip:
pip install sigils
Usage
Here’s a simple example of using Sigils:
from sigils import Sigil
context = {"user": {"name": "Alice"}}
s = Sigil("Hello, %[user.name]!")
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("%[user.greet:user.name]")
print(s % context) # Outputs: Hello, Alice!
s = Sigil("%[user.greet:%%user.name]")
print(s % context) # Outputs: Hello, %user.name! %user.name 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, %[user.name]!" -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!”.
Considerations
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.
Performance
Sigils is designed with performance in mind. In typical use cases, Sigils performs competitively with Python’s built-in string formatting.
License
Sigils is licensed under the MIT License. See the LICENSE file for details.
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