Python Code

Integrate native Python code into a Simulink model

Since R2025a

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  • Python Code block

Libraries:
Simulink / User-Defined Functions

Description

The Python Code block integrates native Python® code into a Simulink® model. Use this block to import external code and customize the integration of your code by specifying the block interface and writing Python code for block initialization, output, and termination.

The Python Code block supports initializing persistent data. Persistent data can include a Python class object. Use persistent variables that store Python objects to preserve state values between time steps.

For steps to integrate your Python code using this block, see Integrate Python Code into Simulink Using Python Code Block.

Note

You must have a compatible version of Python installed in your system to use this block. This might involve installing the corresponding Python development headers in Linux and Mac. You must set the ExecutionMode of Python in MATLAB as InProcess. For more information, see Configure Your System to Use Python.

Python Code is not supported for simulation inside a Dataflow Subsystem. It is also not supported for simulation in rapid accelerator mode when placed within a For Each Subsystem

Examples

Integrate Low Pass Filter Python Code into Simulink Using Python Code Block

Integrate Low Pass Filter Python Code into Simulink Using Python Code Block

Integrate Python Code into Simulink Using Python Code Block.

Ports

Input

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The number of input ports is determined by the number of symbols with Input scope defined in the Ports and Parameters table in the block parameters dialog box. Each input port label is the same as the name of the Input symbol unless you change it by editing the Label field in the Symbols table of the block dialog box.

Python Code does not support array of buses as input.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | bus | fixedpoint

Output

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The number of output ports is determined by the number of symbols with Output scope defined in the Symbols table in the block parameters dialog box. Each output port label is the same as the name of the Output symbol unless you change it by editing the Label field in the Symbols table of the block dialog box.

Python Code does not support array of buses as output.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | Boolean | bus | fixedpoint

Parameters

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Symbols and symbol properties used in the Python code, specified as a table. You must enter the following attributes of each symbol in the table:

  • Name — Symbol name in the code.

    Each symbol you specify represents a python object. The Name field serves as the name given to that Python object.

  • Scope — Scope of the symbol. These scopes are available:

    • Input — Input to the block.

    • Output — Output to the block.

    • Parameter — Block parameter that appears on the block parameter mask. The parameter name is defined by the Label of the symbol.

    • Persistent — Persistent block data, which retains its value from one time step to the next during simulation. A Python Code block configured with persistent variable does not support continuous sample time and stepping back of simulation.

      You can share an arbitrary Python object between code sections or time steps by defining a symbol with Persistent scope and using PythonObject as the Type for the symbol.

  • Label — Label of the symbol. For a symbol with Input or Output scope, the label appears as the port name on the block. For a symbol with Parameter scope, the label appears on the block parameter mask. You cannot define a label for Persistent scope symbols.

  • Type — Data type of the symbol. Select a data type from the drop-down list or specify a custom data type. A PythonObject type can only be set for symbols with scope as Persistent.

  • Size — Size of the symbol data. You can use a size expression to define the size of an output or use -1 to inherit size.

  • Port — Port index of the symbol. For an Input or Output symbol, Port specifies the port index on the block of the port or ports corresponding to the symbol. For a Parameter symbol, Port specifies the order that the symbol appears in the block parameter mask.

Programmatic Use

Block Parameter: SymbolSpec
Type: SymbolSpec object
Value: SymbolSpec object
Default: Empty array of Symbol objects

Sample period, specified in seconds. See Types of Sample Time and Specify Sample Time. If the block defines persistent symbols, you cannot specify a continuous sample time.

Programmatic Use

Block Parameter: SampleTime
Type: string scalar or character vector
Default: "-1"

Output code that the block executes at each time step during simulation, specified as a character vector or string scalar. For example, use this parameter to call a function from external python code, make modifications to the results, and perform operations to pass the results to other blocks.

Programmatic Use

Block Parameter: OutputCode
Type: character vector or string scalar
Value: "" | Python code
Default: ""

Initialization code that the block executes one time at the start of simulation. For example,use this parameter to initialize persistent symbols.

Programmatic Use

Block Parameter: StartCode
Type: character vector or string scalar
Value: "" | Python code
Default: ""

Termination code that the block executes one time at the end of simulation.

Programmatic Use

Block Parameter: TerminateCode
Type: character vector or string scalar
Value: "" | Python code
Default: ""

Block Characteristics

Data Types

Booleana | busa | doublea | fixedpointa | integera | singlea

Direct Feedthrough

no

Multidimensional Signals

yes

Variable-Size Signals

no

Zero-Crossing Detection

no

a Actual data type or capability support depends on block implementation.

Extended Capabilities

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Version History

Introduced in R2025a