running python scripts with matlab

Question

I'm teaching myself a little bit of programming in python and also mathlab. And I need to run a couple of functions I wrote in python with matlab.

I saw this example: In python

 import sys
 def squared():
 y=x*x
 return y
 if __name__ == '__main__':
 x = float(sys.argv[1])
 sys.stdout.write(str(squared(x)))

then in matlab

 [status,result]=system('nameofthescrip', 3)
 status=0
 result=9.0

but, I don't know when I try with my functions it doesn't work.

my program goes something like this:

 def function_1():
 Shows something on screen
 return
 def function_2():
 hear a sound
 return
 def function_3():
 write a number and press a key
 return
 x=[function_1,funciotion_2,function_3]
 random.shuffle(x)

But then I don't know what to put inestead of

 if __name__ == '__main__':
 x = float(sys.argv[1])
 sys.stdout.write(str(squared(x)))

So that I can run it from matlab, just as the example I wrote first!

Answer 1

In the example you give, the code

if __name__ == '__main__':
 x = float(sys.argv[1])
 sys.stdout.write(str(squared(x)))

is run when the script is run, see this SO answer. In your case, the code you want to run when the script is run is

x=[function_1,function_2,function_3]
random.shuffle(x)

so you should put that code inside the if block:

if __name__ == '__main':
 x=[function_1,function_2,function_3]
 random.shuffle(x)

Then in MATLAB you can invoke the Python in a similar way:

[status,result]=system('nameofthescript')

There is no input to your script, so you don't need the second argument of the MATLAB system function. Make sure you have the correct shebang at the top of your script!

• Estefania: ThankS! I understood a lot with your post! Unfortunately I'm having an import-error that I don't know how to fix, I'm working on that right now! But your answer helped me a lot! Thank you so much!

Answer 2

Note that random.shuffle(x) will just rearrange the list x, it won't run or return anything, so your script isn't going to output anything. If you want to run the functions, you'll have to add something like

for f in x:
 f()

to the end of your code, and this will loop through the (shuffled) list of functions and then run each one in that (random) order.

If any of your functions include print, then you should see the results. If you don't, you can try replacing any print with the sys.std.write function you see in the example.

You don't even need the if __name__=='__main__' line unless you want to import your file but not run that part at the end.

• Estefania: Thank you so much! I'm begining to understand how it works.Unfortunately, I'm having an import-error in matlab that I don't seem to be able to fix! However I understood how it worked and could open and run other simpler functions!
• askewchan: You're welcome @Estefania! The import error sounds like another problem, so you might be better off asking a separate question. If my answer helped you please feel free to upvote it or select it with the green checkmark.