Is there a way to run Python from within Mathematica?

Question

I know there is some support for running Mathematica from Python, but is there any way to do the reverse. For example, to import some Python classes and use them in Mathematica?

Answer 1

Building off of @M.R.'s idea, it is possible to set up an interactive python shell using StartProcess as opposed to RunProcess, allowing for much more flexible connectivity between Python and Wolfram without as much overhead. In it's simplest form, one can open a connection, interact with it, and close it using the following example:

path = "e:\\Programs\\python27\\python"; (*insert OS-appropriate path \
to python*)
p = StartProcess[{path, "-i"}]; (*the'-i' argument is important*)
cmd = "print 'hello'"; (*or any valid python expression*)
Pause[1]; (* important!!! *)
WriteLine[p, cmd];
out = ReadString[p, EndOfBuffer]
KillProcess@p;

Pausing after the StartProcess call is important in order to avoid the cmd being sent to the python interpreter before it has finished loading. A much shorter pause can be used on faster computers.

I've put together a short package to streamline python interactivity. The version I've posted below also reads the python shell text (which is delivered on stderr) and prints that to the Message window if the FrontEnd is active or simply Prints it if the command line is being used. It works nicely with simple commands pcmd@"print 'hello'" and I've had success with some sophisticated operations such as web scraping with Splinter and BeautifulSoup. It coughs when trying to use something like Tkinter, but it just doesn't work as opposed to throwing some form of error, making it a bit difficult to debug.

BeginPackage["wlPython`"];

$pythonprocess = Null;
    $pythonpath = "e:\\Programs\\python27\\python";
$pythonpause = 0.250; (* Pause in seconds to receive error information *)
startPython::usage = "Starts the python process";
endPython::usage = "Ends the python process";
pcmd::usage = "issue a python command";


(* Check for FrontEnd and set as appropriate, can be overridden *)
$pyfrontend = $FrontEnd=!=Null;

Begin["`Private`"];

Clear[startPython]
startPython[path_:$pythonpath]:=Module[{err},
    	$pythonprocess = StartProcess[{path,"-i"}];
    wlPython`pyerrcheck[];
    $pythonprocess 
]

Clear[endPython]
endPython[process_:Unevaluated@$pythonprocess]:=Module[{},
    KillProcess@Evaluate@process;
    NotebookWrite[MessagesNotebook[],
    Cell[RawBoxes@ToBoxes["Python process ended",TraditionalForm],"Output"]];
]

Clear[pcmd]
pcmd[cmd_String,process_:Unevaluated@$pythonprocess]:=Module[{status,err,out,p},
    p = Evaluate[process];
    status = ProcessStatus[p];
    If[status=="Running",
    WriteLine[p,cmd];
    wlPython`pyerrcheck[];
    out = ReadString[p,EndOfBuffer]
    ];
    out
]

Clear[pyerrcheck]
pyerrcheck[]:=Module[{err},
    Pause@$pythonpause;
    	err = ReadString[ProcessConnection[$pythonprocess,"StandardError"],EndOfBuffer];
    If[$pyfrontend,
        NotebookWrite[MessagesNotebook[],
        Cell[RawBoxes@ToBoxes[err,TraditionalForm],"Output"]];,
        Print[err];
    ]

]

End[];

EndPackage[];

Answer 2

Here is a more robust solution using Process:

Clear[runPython];
runPython::badCommand  ="Python code failed to run with message `StandardError`";
$pyimports="from random import randint
";
runPython[str_String, imports_:$pyimports] := Module[
    {pyscrpt = ToString[$pyimports<>str, CharacterEncoding->"ASCII"], file=CreateTemporary[], res},
    Export[file,pyscrpt,"Text"];
    res = RunProcess[{"/anaconda/bin/python",file}];
    DeleteFile[file];
    If[res["ExitCode"]!=0, 
        Return @ Failure["badCommand",<|"MessageTemplate" :> runPython::badCommand,"MessageParameters"-> <|"Message" -> res["StandardError"]|>|>],
        Return @ ImportString @ res["StandardOutput"]
    ]
]

I had to use anaconda's python executable - Mathematica was crashing the system's python runtime.

Answer 3

Since 11.2 Mathematica has supported ExternalEvaluate and since 11.3 this functionality has been conveniently available simply by beginning an input cell with > which produces an external code cell:

The output of these cells is a Wolfram Language expression that you can then compute with.

Answer 4

If all you want is to invoke Python scripts and use the output they generate in Mathematica, then simply

pythonOutput = Import["!python fullpathtoscript/your_scipt.py --some_opt arg arg ...", "String"];

is sufficient.

Answer 5

Here is an approach that works on Mac OS X or unix-like systems without the need to explicitly create any temp directory:

code = "print \\\"hello, starting\\\"
for i in [1,2,3]:
\t print i*i
 "

(* ==> 
"print \\\"hello, starting\\\" 
for i in [1,2,3]:
     print i*i
"
*)


RunProcess[$SystemShell, "StandardOutput", 
 "printf \"" <> code <> "\" | python
  exit
  "]

(* ==>
"hello, starting
1
4
9
"
*)

First, I define the string containing the Python code. I included a test message to illustrate how you have to escape the quotation marks using \\\" inside the string, because it's going to be passed into a printf command on the shell command line. THat printf is subsequently piped into python. Note that I didn't have to specify the path because it's found from the SystemShell environment.

The interaction with Mathematica takes place via RunProcess, and the standard output of the Python script is directly captured into Mathematica. Again, it's not necessary to bother with any temporary files in this approach.

Answer 6

There's a "Python link" called Pythonika. I have used it briefly and it works.

What it does:

• translates basic data types, including arbitrary size integers, to/from Python
• makes it possible to implement functions in Python and call them from Mathematica

It does not provide any means to work with classes directly. Also, the implementation is rather hackish using unsafe practices (e.g. symbols are not localized to a context, and this has bitten me). To implement a link properly it would take lot more work.

I made a few basic fixes (e.g. using contexts), but I haven't used the thing in a long time. Contact me if you want the fixes.