I am trying to print out a custom format but am facing an issue.

header = ['string', 'longer string', 'str']
header1, header2, header3 = header
data = ['string', 'str', 'longest string']
data1, data2, data3 = data
len1 = len(header1)
len2 = len(header2)
len3 = len(header3)
len_1 = len(data1)
len_2 = len(data2)
len_3 = len(data3)
un = len1 + len2 + len3 + len_1 + len_2 + len_3
un_c = '_' * un
print(f"{un_c}\n|{header1} |{header2} |{header3}| \n |{data1} |{data2} |{data3}|")

Output:

_____________________________________________
|string |longer string |str|
 |string |str |longest string|

The output I want is this:

_______________________________________
|string |longer string |str           |
|string |str           |longest string|

I want it to work for all lengths of strings using the len function, but I can’t figure it out at all.

>Solution :

Do it in two parts. First, figure out the size of each column. Then, do the printing based on those sizes.

header = ['string','longer string','str']
data = ['string','str','longest string']
lines = [header] * 3 + [data] * 3

def getsizes(lines):
    maxn = [0] * len(lines[0])
    for row in lines:
        for i,col in enumerate(row):
            maxn[i] = max(maxn[i], len(col)+1)
    return maxn

def maketable(lines):
    sizes = getsizes(lines)
    all = sum(sizes)
    print('_'*(all+len(sizes)) )
    for row in lines:
        print('|',end='')
        for width, col in zip( sizes, row ):
            print( col.ljust(width), end='|' )
        print()

maketable(lines)

Output:

_______________________________________
|string |longer string |str            |
|string |longer string |str            |
|string |longer string |str            |
|string |str           |longest string |
|string |str           |longest string |
|string |str           |longest string |

You could change it to build up a single string, if you need that.