python list get values validate position out of ranges

Question

I have a list in Python. Then I want to print the data in each position of the list but if this position is empty replace it with a blank space:

["abcd", "12", "x"] => "a1xb2 c  d  "

I think to make a loop for validating the data in each position. But, when a position in the list is empty, I can't make a validation because I obtain a mistake of index out of range, then it is impossible to make a validation.

How can I get the values of a list in Python in a range of the list that probably can be empty for make a validation.

Answer 1

izip_longest from itertools is your friend. It uses the longest iterable (string here) and replaces the missing characters by the fill value that can be set to the desired space:

from itertools import izip_longest

def f(strings):
    return ''.join(
        map(lambda x: ''.join(x), izip_longest(*strings, fillvalue=' '))
    )


a = ["abcd", "12", "x"]

print(repr(f(a)))

Result:

'a1xb2 c  d  '

A variant with chain instead of map and the second join.

def f(strings):
    return ''.join(
        chain(*izip_longest(*strings, fillvalue=' '))
    )

Intermediate steps of the last method applied on array a:

from pprint import pprint

a1 = izip_longest(*a, fillvalue=' ')
print('# After izip_longest:')
pprint(list(a1))

print('# After chain:')
a1 = izip_longest(*a, fillvalue=' ')
a2 = chain(*a1)
pprint(list(a2))

a1 = izip_longest(*a, fillvalue=' ')
a2 = chain(*a1)
a3 = ''.join(a2)
print('# Result:')
pprint(a3)

Result:

# After izip_longest:
[('a', '1', 'x'), ('b', '2', ' '), ('c', ' ', ' '), ('d', ' ', ' ')]
# After chain:
['a', '1', 'x', 'b', '2', ' ', 'c', ' ', ' ', 'd', ' ', ' ']
# Result:
'a1xb2 c  d  '