Call python from matlab

You can call functionality from Python ® libraries or execute Python statements directly from MATLAB ® .

Access Python Modules

To access Python libraries, add the py. prefix to the Python name. For example:

py.list() % Call built-in function list py.textwrap.wrap('This is a string') % Call wrap function in module textwrap

Run Python Code

To execute Python statements in the Python interpreter from the MATLAB command prompt, use the pyrun function. With this function, you can run code that passes MATLAB types as input and returns some or all of the variables back to MATLAB. For example, suppose that you run this statement in a Python interpreter.

To run the statement from MATLAB, use pyrun . To return the result to a MATLAB variable myList , add «l» as an outputs argument:

myList = pyrun("l = ['A', 'new', 'list']", "l");

Run Python Scripts

To call a Python script from the MATLAB command prompt, use the pyrunfile function. You pass MATLAB data and return variables the same way as with pyrun . For example, create a mklist.py file with these statements:

# Python script file mklist.py: s = 'list' L = ['A', 'new', s]

Run the script from MATLAB:

myListFile = pyrunfile("mklist.py", "L")

myListFile = Python list with no properties. ['A', 'new', 'list']

Access to Python Variables

When you use the py. prefix, MATLAB imports the entire module and can access all functions and classes of the Python code. However, when you execute Python code using the pyrun or pyrunfile functions, if you want to access Python data you must explicitly return Python objects to MATLAB using the outvars argument.

Limitations to pyrun and pyrunfile Functions

Python classes defined using pyrun or pyrunfile cannot be modified if you return an instance of the class to MATLAB. If you need to change class definitions, restart the interpreter session:

terminate(pyenv) pyenv(ExecutionMode="OutOfProcess")

Alternatively, restart MATLAB for «InProcess» .

The pyrun and pyrunfile functions do not support classes with local variables that are initialized by other local variables through methods. For such usage, create a module and access it using the py. prefix.

External Websites

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pyrun

pyrun( code ) executes the Python ® statements in code in the Python interpreter.

Variables created using the pyrun function are persistent. You can use these variables in subsequent calls to pyrun .

outvars = pyrun( code , outputs ) returns any variable generated by Python to MATLAB ® , by specifying the names of the Python variables in the outputs and capturing the returned values in outvars .

outvars = pyrun( code , outputs , pyName=pyValue ) executes the code with assigned input and output variable names using the MATLAB data passed by one or more name-value arguments.

Examples

Execute Python Statements

This example executes these Python statements in the Python interpreter.

greeting = "hello" print(greeting)

Call the Python code from MATLAB.

pyrun(["greeting = 'hello'", "print(greeting)"])

Variable greeting exists only in the Python namespace. MATLAB displays the results of the print statement at the MATLAB command line.

Create MATLAB Variable from Python List

This Python code creates a list of the days of the week.

days = ['Monday','Tuesday','Wednesday','Thursday','Friday']

Create a Python variable days for the list function. In MATLAB, name the variable mllist .

mllist = pyrun("days = ['Monday','Tuesday','Wednesday','Thursday','Friday']","days")

mllist = Python list with no properties. ['Tuesday', 'Monday', 'Wednesday', 'Thursday', 'Friday']

Pass Arguments to Python Operator

This example executes the statement a = b*c in the Python interpreter with the specified input values.

Variables a , b , and c exist only in the Python namespace. However, these variables are available for further calls to pyrun .

Return Results of Python Statement to MATLAB

This example executes b*c in Python and returns the results in a MATLAB variable.

Access Variable in Local Module

This example assigns a local variable to a Python variable to make it accessible in MATLAB.

Create a module localModule.py .

def myFunc(): print('myFunc executed') mvar = 3

Create variable m to access mvar and assign the value to MATLAB variable out .

pyrun("import localModule") out = pyrun("m = localModule.mvar","m")

Input Arguments

code — Python statements
string scalar | string array | character vector | character array | cell array of character vectors | Python code object

One or more Python statements, specified as a string scalar, string array, character vector, character array, cell array of character vectors, or Python code object of a script generated using the Python built-in compile function. Each entry represents a line of Python code.

To call a single-line statement, pass code as a string scalar or character vector. To call multiline Python statements, pass code as a string array, character array, or cell array of character vectors. MATLAB inserts newline characters between elements of multiline statements.

Example: pyrun([«a = 3″,»print(a)»])

pyName=pyValue — Input argument name and value
keyword and value arguments

One or more Input argument names and values to pass to the Python code , specified as keyword and value arguments. pyName is the Python name of a variable, and pyValue is the assigned value. You can specify several name and value pair arguments in any order as pyName1=pyValue1. pyNameN=pyValueN .

Example: pyrun(«b*c»,b=5,c=10) initializes variables b and c for the Python statement b*c .

outputs — Python variable names
string array

One or more Python variable names, specified as a string array. Variables can be local or global. MATLAB assigns the output of code to each variable named by outputs and returns the values in outvars .

Example: mb = pyrun(«b=a+2″,»b»,a=5)

Output Arguments

outvars — MATLAB workspace variable name
MATLAB variable name

One or more MATLAB workspace variable names, returned as valid Python types from code . Specify the names of the Python variables in the outputs argument. If you want to access Python data, then you must explicitly return Python objects to MATLAB using outvars .

To specify multiple outputs, use square brackets. For example, [res1,res2] = pyrun(«a=b*c»,[«a»,»b»],b=5,c=10) returns two outvars , res1 and res2 .

Limitations

Python classes defined using pyrun or pyrunfile cannot be modified if you return an instance of the class to MATLAB. If you need to change class definitions, restart the interpreter session:

terminate(pyenv) pyenv(ExecutionMode="OutOfProcess")

Version History

Introduced in R2021b

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