vcdvcd

What it is and what it does

vcdvcd is a parser for Verilog value change dump (VCD) files, the standard format used by digital simulation tools to record signal waveforms. It provides both a Python library and a command-line tool called vcdcat. The library parses VCD files into an in-memory structure that supports efficient random access to signal values at any point in time, or alternatively can operate in streaming mode with callbacks for memory-constrained applications.

The command-line tool vcdcat formats VCD data for human inspection, with options to display all signals or filter to specific ones, show only signal changes (deltas mode), and view data in a tabular format. The package has no external runtime dependencies, making it straightforward to install and use in both scripting and embedded analysis workflows.

Use it for:

• Inspect and debug digital simulation waveforms from Verilog testbenches without specialized EDA tools.
• Extract specific signal traces from large VCD files for analysis or reporting in automated test frameworks.
• Stream-process VCD data in memory-constrained environments using callback-based parsing.
• Filter and display only relevant signals during simulation result review to reduce output noise.
• Programmatically query signal values at arbitrary time points for post-simulation verification scripts.

Worth the install?

AI-flagged interpretation of the facts on this page — verify before relying

Parses Verilog value change dump (VCD) files and provides both a Python library API for programmatic access and a command-line tool (vcdcat) for viewing and filtering signal data.

Yes, if you work with Verilog simulations and need to parse or inspect VCD files. The package is lightweight, dependency-free, and actively maintained. However, verify the license before use in proprietary projects, since the license treatment is unclear. The aging maintenance status (last release 299 days ago) is not a blocker for stable file format parsing, but check the repository for any open issues relevant to your use case.

Install

vcdvcd on PyPI

pip install vcdvcd

uv add vcdvcd

poetry add vcdvcd

Installing vcdvcd

Before you install

Low friction installation with no runtime dependencies. Last release was 299 days ago; repository is active but aging, with 69 stars and no known security issues.

License in practice

License treatment is unclear—no SPDX identifier or raw license text is available in the package metadata. Verify the actual license before use in proprietary or restricted contexts.

Quickstart

pip install vcdvcd

from vcdvcd import VCDVCD
vcd = VCDVCD('counter_tb.vcd')
signal = vcd['counter_tb.top.out[1:0]']
print(signal.tv)  # List of (time, value) pairs

Verify before relying

• Minimum Python version requirement is not specified in the fact sheet.
• Whether the library handles large VCD files efficiently beyond the streaming callback mode mentioned in the description.

Package facts

Evidence: vcdvcd-2.6.0-py3-none-any.whl

Tags

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