vcdvcd

library2.6.0pypypi✓ verified 88d ago

A Python library for parsing Verilog Value Change Dump (VCD) files, with a built-in command-line viewer vcdcat. Current version 2.6.0, released 2024. Development is stable with occasional updates.

data serialization

pip install vcdvcd

github ↗package ↗

INSTALL

IMPORT

SIG · VCDVCD

vcdvcd

datapythonv2.6.0

Install

1.5s avg

Import

45ms

Disk

16MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v2.6.0 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.95 runs

installs and imports cleanly · install 0.0s · import 0.046s · 17.8MB

glibc

py 3.10–3.95 runs

installs and imports cleanly · install 1.5s · import 0.044s · 18MB

16MB installed

● package 16MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

VCDVCD

✓ from vcdvcd import VCDVCD

Main parser class.

Opens a VCD file, iterates over signals, and retrieves signal data.

from vcdvcd import VCDVCD # Parse a VCD file vcd = VCDVCD('trace.vcd') # Iterate over signals for signal in vcd.signals: print(signal.reference, signal.times, signal.tv) # Get a specific signal by reference (hierarchical name) signal_data = vcd.get_signal_data('top.clk') if signal_data: print(signal_data.tv)

vcdcat --version

Debug

Known issues

gotchaSignal hierarchy uses dots internally; signals are stored with full hierarchical reference (e.g., 'top.sub.sig') even if the VCD uses dollar var. Querying without the full path will return None.

fix

Use vcd.signals to list available references and use the full dotted name.

affects: all

gotchaTime values are stored as strings by default. vcds and changes are lists with time as first element (also string).

fix

Convert times to int if needed: int(time_value).

affects: all

deprecatedThe old import from vcdvcd import VCD is deprecated and may be removed. Use VCDVCD.

fix

Change import to: from vcdvcd import VCDVCD

affects: >=2.0.0

Errors

Common errors & fixes

ModuleNotFoundError: No module named 'vcdvcd'

Library not installed.

fix

pip install vcdvcd

AttributeError: 'VCDVCD' object has no attribute 'signals'

Using an old import or attribute name; signals may not be populated if VCD file has no signals, or incorrect version.

fix

Ensure you are using from vcdvcd import VCDVCD and that the file is valid. Check vcd.signals is a list.

Upgrade

Version history

2.6.0latest on PyPI · released Oct 19, 2025

Audit

Dependencies

No dependency data recorded yet.

Agent activity

42 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/cirosantilli/vcdvcd ↗

packagehttps://pypi.org/project/vcdvcd/ ↗