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Python

Posted by Shane Singh
Shane Singh
5,440 Points

Need some clarification.

new_list = []

undersc = '_'

for i in range(1, rows + 1):

      new = []

      for j in range(1, columns + 1)     

        new.append(undersc if j > i else 'Z')

      new_list.append(new)

for c in range(len(new_list[0])): 

     print()

for r in range(len(new_list)):

     for c in range(len(new_list[0]))       

       array = print((new_list[r][c]), end=" ")   

     print()

return array

My confusion comes from the last for loops: for r in range(len(new_list)): and for c in range(len(new_list[0])). what does (len(new_list[0])) in this examples measure? Any help would be greatly appreciated.

[MOD: added ```python markdown formatting -cf]

Brendan Whiting
.a{fill-rule:evenodd;}techdegree seal-36
Brendan Whiting
Front End Web Development Techdegree Graduate 84,738 Points

Where is this code from? What are you rows and columns variables referring to? It seems like you're performing some kind of operation on a matrix, but it would help to have access to the matrix.

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,468 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,468 Points

From the code, new_list is a list of lists. The two range arguments mean:

  • len(new_list) is the length, or number of items in new_list
  • len(new_list[0]) is the length or number of items in the first element of new_list

In other words, given the list with two elements, each being a list:

new_list = [ ['a', 'b', 'c'], [1, 2, 3, 4] ]

len(new_list) is 2, while new_list[0] is ['a', 'b', 'c'] and len(new_list[0]) is 3