Transposing my array?

Question

I am a novice programmer in python and was wondering if I can get a little help. The code I am about to show below prints out a simple array based on the users input for # of rows and # of columns.

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

The console outputs the following:

Z _  _  _  _

Z  Z  _  _  _

Z  Z  Z   _  _

I am completely lost as to how I would transpose my array in other words swap the columns with the rows. Any help would be greatly appreciated!

Answer 1 · 2015-12-08T19:45:28Z

December 8, 2015 7:45pm

You have all the information you need. To reverse the columns and rows exchange your inner and outer loops:

# initial print loop
    for r in range(len(new_list)):
        for c in range(len(new_list[0])):
            array = print((new_list[r][c]), end=" ")
        print()


# transposed print loops
    for c in range(columns):
        for r in range(rows):
            array = print((new_list[r][c]), end=" ")
        print()

Compressing and cleaning up your code a bit:

def array2(rows, columns):
    new_list = []
    undersc = '_'

    # i and j are relative counters, no need to use 1-based counting
    for i in range(rows):
        new = []
        for j in range(columns):
            new.append(undersc if j > i else 'Z')
        new_list.append(new)

    # this prints out many blank lines. Not clear why it's needed
    # for c in range(len(new_list[0])):
    #     print()

    for c in range(columns):
        for r in range(rows):
            # print does not return object, assignment to 'array' not needed
            print((new_list[r][c]), end=" ")
        print()

    # no value being returned, explicit 'return' not needed
    # return array

Produces:

>>> array2(3, 4)
Z Z Z 
_ Z Z 
_ _ Z 
_ _ _

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Shane Singh

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Transposing my array?

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Chris Freeman

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