How do I extract index 0 of each list with Python?-CodePudding

I have the following list named "rows":

[['1', 'Peter', 'Cookies'], ['2', 'Sarah', 'Chocolate'], ['3', 'Daria', 'Lollies']]

I'm trying to store the elements at index 0 within each list in a variable called ID with set comprehension but am struggling.

I've tried the following:

ID = {[row[0] for row in rows]}

but get the error:

unhashable type list

I need to find a solution by using list comprehension.

CodePudding user response：

THe error : unhashable type list is because you are trying to use a list as a key in a dictionary. Try this to get the first element of each list.

ID = [row[0] for row in rows] 
# ['1', '2', '3']

CodePudding user response：

CODE:

import numpy as np
rows = [['1', 'Peter', 'Cookies'], ['2', 'Sarah', 'Chocolate'], ['3', 'Daria', 'Lollies']]
ID = [rows[row][0] for row in range(len(rows))]
ID

OUTPUT:

['1', '2', '3']