The PyVCD package writes Value Change Dump (VCD) files as specified in IEEE 1364-2005.

Read the documentation.

Visit PyVCD on GitHub.

>>> import sys
>>> from vcd import VCDWriter
>>> with VCDWriter(sys.stdout, timescale='1 ns', date='today') as writer:
...     counter_var = writer.register_var('a.b.c', 'counter', 'integer', size=8)
...     real_var = writer.register_var('a.b.c', 'x', 'real', init=1.23)
...     for timestamp, value in enumerate(range(10, 20, 2)):
...         writer.change(counter_var, timestamp, value)
...     writer.change(real_var, 5, 3.21)
$date today $end
$timescale 1 ns $end
$scope module a $end
$scope module b $end
$scope module c $end
$var integer 8 ! counter $end
$var real 64 " x $end
$upscope $end
$upscope $end
$upscope $end
$enddefinitions $end
#0
$dumpvars
b1010 !
r1.23 "
$end
#1
b1100 !
#2
b1110 !
#3
b10000 !
#4
b10010 !
#5
r3.21 "