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I was wondering how I can translate the following code into python from matlab script? Especially the content within the for loop and the writematrix last line of code, I have been stuck on. This program codes for copying the second row all columns of every excel file within a folder and creates an output excel file in the same folder which has the second row all columns of every excel file within the folder into a single matrix. Thank you, and a happy new year.

clc
clearvars
fileDir = cd;
outfile = 'OUT.xlsx'; %Output file name
fileNames = dir(fullfile(fileDir,'*.CSV'));
fileNames_sorted = natsortfiles({fileNames.name});
M= length (fileNames_sorted);
second_col= [];

for f = 1:M
    raw = importdata( fullfile(fileDir, fileNames_sorted{f}));
    second_col= [second_col raw(:,2)];  % extract the second column
end
writematrix(second_col,fullfile(cd,outfile))
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1 Answer 1

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You have to install packages first

pip install pandas, numpy

from pathlib import Path
import pandas as pd 
import numpy as np

clear 

[del globals()[name] for name in dir() if not name.startswith('_')]

fileDir = Path.cwd()
outfile = Path(fileDir, 'OUT.csv')
fileNames = sorted(fileDir.glob('*.csv'))

second_col= []

for file in fileNames:
    df = pd.read_csv(file)
    second_col.append(df.iloc[:, 0])
    
matrix = np.array(second_col)
np.savetxt(outfile, matrix, delimiter=",")

In case you need to transpose the matrix save like this

np.savetxt(outfile, matrix.T, delimiter=",")

Other ways of saving

Make sure you use tabs in the for loop. Have fun

EDIT

Running dir() within a list comprehension wont work see for explanation dir inside function. Here is an alternative.


from pathlib import Path
import pandas as pd 
import numpy as np

def clearvars():    
    for el in sorted(globals()):
        if '__' not in el:
                print(f'deleted: {el}')
                del el
clearvars() 
clear 

fileDir = Path.cwd()
outfile = Path(fileDir, 'OUT.csv')
fileNames = sorted(fileDir.glob('*.csv'))

second_col= []

for file in fileNames:
    df = pd.read_csv(file)
    second_col.append(df.iloc[:, 0])

matrix = np.array(second_col)
np.savetxt(outfile, matrix, delimiter=",")

You can delete this line print(f'deleted: {el}') if you like. It's just for clarification.

sorted(globals() or dir()contains a dictionary of all variables (namespace) used by python to run that code. Python relevant variables start and end with a '__'. You a basically looping through the names in the namespace and deleting all the names that you created in your script.

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14 Comments

Hi @RSale. I was wondering what the line: [del globals()[name] for name in dir() if not name.startswith('_')] does? Also how can I choose the directory where my program works? thanks
If you are new to python and you are using vscode. Checkout inteactive windows. This will blow your mind ;)
Did the rest of the code work? I don't have Matlab installed right now. So I couldn't varify.
Hi @RSale, Thanks for continuing with your help, unfortunately when I run the code through Spyder it runs the directory through my downloads file outputting an empty excel file. - when I select the directory to be in a specific file directory it returns to the downloads folder unfortunately.
Sorry that was my mistake rglob should be glob``. rglob is the recursive `version. You can also try adding the path as string directly fileDir = "filepath" ``` .
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