backcall
Specifications for callback functions passed in to an API
Decision gist · record as of 2026-08-14
Yes, if you are maintaining a library with a stable callback API and want lightweight signature validation without dependencies. No, if you need active maintenance or are starting a new project—the package is abandoned and there are no recent updates. Consider it for mature, low-change codebases only.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Installation is straightforward with no runtime dependencies.
- However, the package is abandoned—last release was 2020-06-09 and no commits since then—so it will not receive bug fixes or maintenance.
License · maintenance · safety
permissive license (permissive) — Licensed under BSD (permissive), so you can use it freely in commercial and open-source projects without copyleft obligations.
last release 2020-06-09 (2257 days) · last repo commit 2020-06-09 · 19 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 14,815,737 downloads/mo, #1,216 on PyPI
Alternatives
Verify before relying
from backcall import callback_prototype
@callback_prototype
def handle_ping(sender, delay=None):
pass
callback = handle_ping.adapt(your_callback_function)- Whether the package works correctly with modern Python versions (classifiers list Python 2.7 and Python 3, but no specific version bounds are declared)
What it is and what it does
backcall is a small utility for specifying and enforcing callback function signatures in APIs. When you accept callbacks from users of your library, backcall lets you define a prototype function that describes the expected signature, then automatically adapts incoming callbacks to match it. If a callback has fewer parameters than the prototype, backcall wraps it to discard extras; if it requires more, backcall raises a TypeError at registration time rather than at call time.
The package has no runtime dependencies and installs cleanly. It is designed for library authors who want to evolve their callback APIs without breaking existing user code. However, the project has been abandoned since 2020 with no recent maintenance, so it should only be used in stable, low-change codebases or as a reference for implementing similar validation logic.
Use it for
- Library authors defining stable callback APIs that may evolve over time while maintaining backward compatibility
- Validating event handler signatures before registering them in event systems or plugin frameworks
- Adapting third-party callbacks to match your API's expected parameter list without manual wrapping
- Catching callback signature mismatches early at registration time rather than at runtime
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, if you are maintaining a library with a stable callback API and want lightweight signature validation without dependencies.
No, if you need active maintenance or are starting a new project—the package is abandoned and there are no recent updates. Consider it for mature, low-change codebases only.
Install
backcall on PyPI
Before you install
Installation is straightforward with no runtime dependencies. However, the package is abandoned—last release was 2020-06-09 and no commits since then—so it will not receive bug fixes or maintenance.
License in practice
Licensed under BSD (permissive), so you can use it freely in commercial and open-source projects without copyleft obligations.
Quickstart
from backcall import callback_prototype
@callback_prototype
def handle_ping(sender, delay=None):
pass
callback = handle_ping.adapt(your_callback_function)Verify before relying
- Whether the package works correctly with modern Python versions (classifiers list Python 2.7 and Python 3, but no specific version bounds are declared)
Package facts
| License | permissive license permissive |
| Python support | Not specified |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | None |
| Maintenance | Abandoned 2,257 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 14,815,737 / month, #1,216 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | License :: OSI Approved :: BSD LicenseProgramming Language :: Python :: 2Programming Language :: Python :: 2.7Programming Language :: Python :: 3 |
Evidence: backcall-0.2.0-py2.py3-none-any.whl
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