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Running a python script in matlab

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Hi, I tried to run a python script in matlab. I used the function system.So fa so good.
The pyhton script uses two input variables. In matlab I can enter one and then it runs without problems but when I try to enter two separate variables I always get an error.
systemCommand = ['python sqd.py ',num2str(a),num2str(omtrek)]
[status, result] = system(systemCommand);
This is the error:
status =
1
result =
Traceback (most recent call last):
File "sqd.py", line 10, in <module>
sys.stdout.write(str(squared(x)))
TypeError: squared() takes exactly 2 arguments (1 given)
Can someone help me?
Thanks!
  1 Comment
Charles
Charles on 29 Aug 2017
This is interesting I am new to python, and I am trying to to do the dame thing Does the solution in fact work? I am keen to try it. I literally do not know python at all, neither am I am a programmer but I find it all fascinating and I move forward by trail and error. Some how I make progress. I will try this, but what infrastructure do you have? I have Matlab, 2017a and Python 3.6 Do i need anything else? I am reading that the former does not support the latter. Any thoughts?

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Accepted Answer

Friedrich
Friedrich on 16 Jan 2013
Edited: Friedrich on 16 Jan 2013
Hi,
when modifying your script to:
import sys
def squared(a,omtrek):
b = (omtrek/2)-a
return b
if __name__ == '__main__':
x = float(sys.argv[1])
y = float(sys.argv[2])
sys.stdout.write(str(squared(x,y)))
and calling it from MATLAB:
>>!C:\Python32\python.exe sqd.py 1 2
it works fine for me. Or in your way:
>> a = 1
>> omtrek = 2
>>systemCommand = ['C:\Python32\python.exe sqd.py ',num2str(a),' ',num2str(omtrek)]
>> system(systemCommand)
0.0
ans =
0
  1 Comment
Aravind Sasikumar
Aravind Sasikumar on 18 Apr 2016
Hello, The above code works for me too. The program is running but I am not able to get back the value of b in Matlab. I want to perform further calculations with the value of b.
import sys
def add(a,c):
b=a+c
return b
if _name_ == 'main':
x=float(sys.argv[1])
y=float(sys.argv[2])
sys.stdout.write(str(add(x,y)))
Why am I not getting the value of b back in matlab ?

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More Answers (7)

Bo Li
Bo Li on 18 Apr 2016
Why not using Python Interface?
The MATLAB statement can be as simple as following:
>> b=py.sqd.squared(10,30)

Shashank Prasanna
Shashank Prasanna on 15 Jan 2013
Could you try the above with a space between the two arguments?
systemCommand = ['python sqd.py ',num2str(a),' ',num2str(omtrek)]

Tom Leblicq
Tom Leblicq on 16 Jan 2013
This is the python script:
import sys
def squared(a,omtrek):
b = (omtrek/2)-a
return b
if __name__ == '__main__':
x = float(sys.argv[1])
sys.stdout.write(str(squared(x)))
It's very easy code, but this is just a test for a more complex program I would like to run.
In python it works. In Matlab it doesn't. It's true that the code needs two inputs. But my question is how can I give two inputs using matlab?

Tom Leblicq
Tom Leblicq on 16 Jan 2013
You are right Friedrich, this works! Thanks!
But by doing this I have another problem. The python code calculates the value of a parameter "b". I need this parameter in matlab for further processing. The correct value appears on my screen but I can't handle it. For example like this:
2.0>>

Aysha Ashraf
Aysha Ashraf on 21 Dec 2017
Can any one help me how to integrate this python code to matlab, i want to run this python program in matlab...
#Load dependencies import pandas as pd import numpy as np from sklearn.preprocessing import StandardScaler from matplotlib import* import matplotlib.pyplot as plt from matplotlib.cm import register_cmap from matplotlib.mlab import PCA from sklearn.decomposition import PCA
from scipy import stats #from wpca import PCA from sklearn.decomposition import PCA as sklearnPCA import seaborn
#Load movie names and movie ratings movies = pd.read_csv('movies.csv') ratings = pd.read_csv('ratings.csv') ratings.drop(['timestamp'], axis=1, inplace=True) # def replace_name(x): return movies[movies['movieId']==x].title.values[0] # ratings.movieId = ratings.movieId.map(replace_name) # M = ratings.pivot_table(index=['userId'], columns=['movieId'], values='rating') m = M.shape #posesall = pd.read_csv('FileName_Poses.csv') df1 = M.replace(np.nan, 0, regex=True) X_std = StandardScaler().fit_transform(movies) #Step 2: Covariance Matrix and Eigendecomposition mean_vec = np.mean(X_std, axis=0) cov_mat = (X_std - mean_vec).T.dot((X_std - mean_vec)) / (X_std.shape[0]-1) print('Covariance matrix \n%s' %cov_mat) print('NumPy covariance matrix: \n%s' %np.cov(X_std.T)) #Perform eigendecomposition on covariance matrix cov_mat = np.cov(X_std.T) eig_vals, eig_vecs = np.linalg.eig(cov_mat) print('Eigenvectors \n%s' %eig_vecs) print('\nEigenvalues \n%s' %eig_vals) # Step 3: Selecting Principal Components # Visually confirm that the list is correctly sorted by decreasing eigenvalues eig_pairs = [(np.abs(eig_vals[i]), eig_vecs[:,i]) for i in range(len(eig_vals))] print('Eigenvalues in descending order:') for i in eig_pairs: print(i[0]) pca = PCA(n_components = 93) All_poses_pca = pca.fit_transform(movies) Variance = (pca.explained_variance_ratio_)
#Explained variance pca = PCA().fit(X_std) plt.plot(np.cumsum(pca.explained_variance_ratio_)) plt.title('Scree Plot') plt.xlabel('Number of principal components') plt.ylabel('Cumulative explained variance') plt.show()

Yodish
Yodish on 12 Apr 2018
It works for me as well, but it is very slow. It takes 0.2 sec to call a sum function from Python
Any ideas on how to speed it up? Where is the bottle neck?

Agapi Dav
Agapi Dav on 31 Jul 2018
Hello everyone! I have some images read in matlab and I want to process them in python and them return them to matlab for further processing.
Everything with the systemCommand works, however, even though I can import variables from matlab to python, because they are already in the workspace, I cannot return variables (e.g. images) back to matlab, when running the python script. Till now, in order to make it work, I save the python-processed images and then read them again from matlab.
I would like to ask if there is a more efficient way. In other words, in the example of Tom Leblicq, I would like to return the parameter b in matlab for further processing.
Thank you in advance!
  1 Comment
Abdelwahab Afifi
Abdelwahab Afifi on 12 Jan 2021
The following command will return b in the workspace of MATLAB
b=py.sqd.squared(2)

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