Lists

[zowhair]

Dear friends can you please help me???

vec = [[1,2,3],[4,5,6],[7,8,9,0]]
print([num for elem in vec for num in elem]) **huh** 

what does the second statement meant?

[Windspar]

It a list expression:
Equal to

vec = [[1,2,3],[4,5,6],[7,8,9,0]]
output = []
for elem in vec:
    for num in elem:
        output.append(num)
print(output)

[Larz60+]

And it's called a list comprehension explained here: https://www.programiz.com/python-program...prehension
or here: http://www.pythonforbeginners.com/basics...-in-python