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I am struggeling with python now. i'm trying this script. I am sure this is a very common syntax in python, but it is so generic I can't find any explanation that make sense to me.

Can you help me to understand the meaning of [:, 0] and [:, 1:] in the following lines of code?

syms = np.genfromtxt('people.csv', dtype=str, delimiter=',')[:, 0] 

X = np.genfromtxt('people.csv', dtype=object, delimiter=',')[:, 1:]

people.csv

|       |   |   | |  
|-------|---|---|-|  
|Marc   | .2| -2|A|  
|Martine|-.2|  0|A|  
|Max    | .2| .2|A|  
|Maxine | .2| .1|A|
Bill the Lizard
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Duccio Fabbri
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1 Answers1

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That's using slice notation to extract specific rows and columns from the dataset.

[:, 0] means all rows, column 0.

[:, 1:] means all rows, columns 1 through n (all columns except 0).

See Understanding slicing for a good explanation of Python slicing notation.

Bill the Lizard
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  • I didn't know this is the "slice notation". Searching "Slicing notation python" returns lots of docs, I just missed what to search for. – Duccio Fabbri Nov 28 '22 at 15:23