How to iterate through letters in a list

Question

I am trying to iterate through all the letters in the list, although i am not making much progress.

EX:

L = ["pizza","burger","shawarma","nuggets"]

the program should output

p b s n
i u h u
z r a g

and so on, basically iterating the words by their indexes.

I tried doing it by a for loop like this:

newlist = [i[0] for i in a]

Which only outputs the first letters in the list.
I am wondering about how to iterate it to have all the indexes if it is possible.

Asked By: LeliPopek

||

Source

Answer 1

Try this:

>>> list(zip(*lst))
[('p', 'b', 's', 'n'),
 ('i', 'u', 'h', 'u'),
 ('z', 'r', 'a', 'g'),
 ('z', 'g', 'w', 'g'),
 ('a', 'e', 'a', 'e')]

# If you want a string with space between chars use "' '.join"
>>> list(map(' '.join, zip(*lst)))
['p b s n', 'i u h u', 'z r a g', 'z g w g', 'a e a e']

Explanation:

# convert string to list of chars
>>> [list(l) for l in lst]
[['p', 'i', 'z', 'z', 'a'],
 ['b', 'u', 'r', 'g', 'e', 'r'],
 ['s', 'h', 'a', 'w', 'a', 'r', 'm', 'a'],
 ['n', 'u', 'g', 'g', 'e', 't', 's']]
#  ^ ,  ^ ,  ^ ,  ^ ,  ^    ^ ,  ^,   ^ NB. If you want to continue this zip for other elements, you need to use 'itertools.zip_longest'
#  ^ ,  ^ ,  ^,   ^ ,  ^  <- we need 'zip'. 

# Now we need 'zip' for gathering ('p', 'b', 's', 'n') ,  ...
>>> list(zip(*lst))
[('p', 'b', 's', 'n'),
 ('i', 'u', 'h', 'u'),
 ('z', 'r', 'a', 'g'),
 ('z', 'g', 'w', 'g'),
 ('a', 'e', 'a', 'e')]

Answered By: I'mahdi

Answer 2

There’s no need to use list on the words – iterating over a string yields individual characters:

>>> food = ["pizza","burger","shawarma","nuggets"]

>>> for line in (' '.join(row) for row in zip(*food)):
...     print(line)
...
p b s n
i u h u
z r a g
z g w g
a e a e

If you needed to use the longest word’s length, you could use itertools.zip_longest:

>>> from itertools import zip_longest

>>> for row in zip_longest(*food, fillvalue=' '):
...     print(' '.join(row))
...
p b s n
i u h u
z r a g
z g w g
a e a e
  r r t
    m s
    a

To handle the longest word without using zip_longest, one approach would be to first normalize the words so they are all the same length, and then use the original zip approach:

>>> longest = max(len(word) for word in food)

>>> normalized = [word + (' ' * (longest - len(word))) for word in food]

>>> normalized
['pizza   ', 'burger  ', 'shawarma', 'nuggets ']

>>> for row in zip(*normalized):
...     print(' '.join(row))
...
p b s n
i u h u
z r a g
z g w g
a e a e
  r r t
    m s
    a

Answered By: dskrypa

How to iterate through letters in a list

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