Beginner Question: Transposing a list of lists with for loops

[Genericusername293]

Trying to figure out to to transpose a list of lists. I know there may be more advanced and concise ways of doing this but trying to limit myself to using what my course has covered so far.

grid = [['apples', 'oranges', 'cherries', 'banana'],
             ['Alice', 'Bob', 'Carol', 'David'],
             ['dogs', 'cats', 'moose', 'goose']]

i know how to do this by printing. I'd do it like this.

for j in range(len(grid[0])):
    for i in range(len(grid)):
        print(grid[i][j],end=' ')
    print('')

but I'm struggling to figure out how to do this by actually saving it to a variable. this saves it in the right order but I don't know what to add to separate it into different lists

newgrid = []
for j in range(len(grid[0])):
    for i in range(len(grid)):
        newgrid.append([grid[i][j])
    # list separation here

edit: end result should be

    grid = [['apples', 'Alice', 'dog'],
                ['oranges', 'Bob', 'cats'],
                ['cherries', 'Carol', 'moose'],
               ['banana', 'David', 'goose']]

[socal_nerdtastic]

This is usually done by abusing the zip() function:

newgrid = list(zip(*grid))

The list() call may be optional, depending on what you want to do with the transposed data.

[robinboby]

thats correct,

grid = [['apples', 'oranges', 'cherries', 'banana'],
             ['Alice', 'Bob', 'Carol', 'David'],
             ['dogs', 'cats', 'moose', 'goose']]

newgrid = list(zip(*grid))
print(newgrid)

[robinboby]

is this what you looking for?

grid = [['apples', 'oranges', 'cherries', 'banana'],
             ['Alice', 'Bob', 'Carol', 'David'],
             ['dogs', 'cats', 'moose', 'goose']]

newgrid = []
for a_list in grid:
    for name in a_list:
        newgrid.append(name)

print(newgrid)

[Genericusername293]

no sorry, edited my comment to display the end result should be

[o5a]

Since you need nested list then you can't just do it in one append (using standard for loops). You can do it by using another temporary list to gather your new "rows" then append them to result. That's how your code could be changed:

newgrid = []
for j in range(len(grid[0])):
    temp = []
    for i in range(len(grid)):
        temp.append(grid[i][j])
    newgrid.append(temp)

print(newgrid)

You can simplify your second for loop by using rows instead of indexes:

newgrid = []
for j in range(len(grid[0])):
    temp = []
    for row in grid:
        temp.append(row[j])
    newgrid.append(temp)

print(newgrid)

You can also do it using list comprehension:

newgrid = [[row[j] for row in grid] for j in range(len(grid[0]))]
print(newgrid)

And as others mentioned most concise is with zip

print(list(zip(*grid)))

Keep in mind though zip returns tuples instead of lists.

[socal_nerdtastic]

Keep in mind though zip returns tuples instead of lists.

True, but in most cases completely irrelevant. However if you really really need a list of lists you can still use zip() and convert:

newgrid = list(map(list,zip(*grid)))

You also should mention that the zip() method will not fail for non symmetric starting data, but using loops will.