vcdvcd
Python Verilog value change dump (VCD) parser library + the nifty vcdcat VCD command line viewer
Decision gist · record as of 2026-08-14
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.AI-flagged interpretation of the facts on this page — verify before relying
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 · maintenance · safety
(unclear) — 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.
last release 2025-10-19 (299 days) · last repo commit 2025-10-19 · 69 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 132,679 downloads/mo, #11,543 on PyPI
Alternatives
Verify before relying
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- 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.
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 on it.
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
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) pairsVerify 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
| License | Not declared unclear |
| Python support | Not specified |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | None |
| Maintenance | Aging 299 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 132,679 / month, #11,543 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
Evidence: vcdvcd-2.6.0-py3-none-any.whl
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