Reading and Manipulating NetlistsΒΆ

PyLTSpice has the ability to read and manipulate netlist files using the SpiceEditor class.

The SpiceEditor class inherits almost all functions from SpiceCircuit class. The SpiceCircuit class allows manipulation of circuit elements such as resistors, capacitors, transistors and so on, as well as subcircuit parameters.

The SpiceEditor extends these funcionalities and adds all the functions needed to read and write netlists to the disk, as well as defining top level simulation directives, such as .TRAN and .AC for example.

The rationale for this division is to allow to manipulate not only elements that exist at the top level, but also to manipulate elements that exit inside of sub-circuits. In Example 2 there is small example where the value of a component inside a subcircuit is changed.

When all the changes are made, the write_netlist(<filename>) needs to be called in order for the updates to be registered.

Do not update the original file. It is always safer to keep the original file unchanged. This helps when debuging problems, and also allows the script to revert to the initial condition by using the reset_netlist() method.

Example 1: Setting parameters inside a flat netlist.

#read netlist
import PyLTSpice
net = PyLTSpice.SpiceEditor("")  # Loading the Netlist

net.set_parameters(res=0, cap=100e-6)  # Updating parameters res and cap
net.set_component_value('R2', '2k')    # Updating the value of R2 to 2k
net.set_component_value('R1', 4000)    # Updating the value of R1 to 4k
net.set_element_model('V3', "SINE(0 1 3k 0 0 0)")  # changing the behaviour of V3

# add instructions
    "; Simulation settings",
    ".param run = 0"

net.write_netlist("")  # writes the modified netlist to the indicated file

Example 2: Updating components inside a subcircuit

#read netlist
import PyLTSpice
net = PyLTSpice.SpiceEditor("")

net.set_component_value('R1', 1000)      # Sets the value of R1 to 1k
net.set_component_value('XU1:Ra', '1k')  # Sets the value of Ra inside of XU1 to 1k

See the class documentation for more details :

  • PyLTSpice.SpiceEditor

  • PyLTSpice.SpiceCircuit