Skip to content

Instantly share code, notes, and snippets.

Last active November 30, 2022 16:42
What would you like to do?
Short python script to read ngspice raw binary files
# MIT license:
# See
# for a more complete library. Isotel's version is GPL licensed
from __future__ import division
import numpy as np
BSIZE_SP = 512 # Max size of a line of data; we don't want to read the
# whole file to find a line, in case file does not have
# expected structure.
MDATA_LIST = [b'title', b'date', b'plotname', b'flags', b'no. variables',
b'no. points', b'dimensions', b'command', b'option']
def rawread(fname: str):
"""Read ngspice binary raw files. Return tuple of the data, and the
plot metadata. The dtype of the data contains field names. This is
not very robust yet, and only supports ngspice.
>>> darr, mdata = rawread('')
>>> darr.dtype.names
>>> plot(np.real(darr['frequency']), np.abs(darr['v(out)']))
# Example header of raw file
# Title: rc band pass example circuit
# Date: Sun Feb 21 11:29:14 2016
# Plotname: AC Analysis
# Flags: complex
# No. Variables: 3
# No. Points: 41
# Variables:
# 0 frequency frequency grid=3
# 1 v(out) voltage
# 2 v(in) voltage
# Binary:
fp = open(fname, 'rb')
plot = {}
count = 0
arrs = []
plots = []
while (True):
mdata = fp.readline(BSIZE_SP).split(b':', maxsplit=1)
if len(mdata) == 2:
if mdata[0].lower() in MDATA_LIST:
plot[mdata[0].lower()] = mdata[1].strip()
if mdata[0].lower() == b'variables':
nvars = int(plot[b'no. variables'])
npoints = int(plot[b'no. points'])
plot['varnames'] = []
plot['varunits'] = []
for varn in range(nvars):
varspec = (fp.readline(BSIZE_SP).strip()
assert(varn == int(varspec[0]))
if mdata[0].lower() == b'binary':
rowdtype = np.dtype({'names': plot['varnames'],
'formats': [np.complex_ if b'complex'
in plot[b'flags']
else np.float_]*nvars})
# We should have all the metadata by now
arrs.append(np.fromfile(fp, dtype=rowdtype, count=npoints))
fp.readline() # Read to the end of line
return (arrs, plots)
if __name__ == '__main__':
arrs, plots = rawread('test.raw')
# Local Variables:
# mode: python
# End:
Copy link

@snmishra I tried to read a raw fine with your script, its saying 'darr' is not defined. Can you please check what i am missing. Thank you in advance.

My raw file is here:

Copy link

@Varat7v2 Looks there was a typo. I changed print(darr) to print(arrs)

Copy link

@snmishra Thank you I changed it. However, it is showing empty array. Is there any mistake in the raw file that I have generated? It is automatically exported from the LTSpice software.

Copy link

Works really well out of the box. Thank you very much!

Copy link

Thanks @cardosorapha

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment