最后一行是做什么的？

Question

apb = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

for i in range(26):
    s = apb[i:26] + apb[0:i]
    print("{:2d}    {}    ".format(i, s))

Supposed to output this

Sorry just started learning python and this can seem like a dumb question. I tried googling but it keeps telling me it has something to do with 2d array and I definietly know thats not the answer I am looking for.

I understand everything until the last line.

What does: print("{:2d} {} ".format(i, s)) do?

Answer 1

The format function replaces {} (a placeholder) with a variable. {:2d} is similar to the %2d printf format specifier in the C language where it reserves 2 spaces on the console for the variable. For example '{:2d}'.format(2) would print ' 2' . If you want, you can use {} , which would yield the same result, but the letters would not be aligned the same. With {:2d} :

 0    ABCDEFGHIJKLMNOPQRSTUVWXYZ    
 1    BCDEFGHIJKLMNOPQRSTUVWXYZA    
 2    CDEFGHIJKLMNOPQRSTUVWXYZAB    
 3    DEFGHIJKLMNOPQRSTUVWXYZABC    
 4    EFGHIJKLMNOPQRSTUVWXYZABCD    
 5    FGHIJKLMNOPQRSTUVWXYZABCDE    
 6    GHIJKLMNOPQRSTUVWXYZABCDEF    
 7    HIJKLMNOPQRSTUVWXYZABCDEFG    
 8    IJKLMNOPQRSTUVWXYZABCDEFGH    
 9    JKLMNOPQRSTUVWXYZABCDEFGHI    
10    KLMNOPQRSTUVWXYZABCDEFGHIJ    
11    LMNOPQRSTUVWXYZABCDEFGHIJK    
12    MNOPQRSTUVWXYZABCDEFGHIJKL    
13    NOPQRSTUVWXYZABCDEFGHIJKLM    
14    OPQRSTUVWXYZABCDEFGHIJKLMN    
15    PQRSTUVWXYZABCDEFGHIJKLMNO    
16    QRSTUVWXYZABCDEFGHIJKLMNOP    
17    RSTUVWXYZABCDEFGHIJKLMNOPQ    
18    STUVWXYZABCDEFGHIJKLMNOPQR    
19    TUVWXYZABCDEFGHIJKLMNOPQRS    
20    UVWXYZABCDEFGHIJKLMNOPQRST    
21    VWXYZABCDEFGHIJKLMNOPQRSTU    
22    WXYZABCDEFGHIJKLMNOPQRSTUV    
23    XYZABCDEFGHIJKLMNOPQRSTUVW    
24    YZABCDEFGHIJKLMNOPQRSTUVWX    
25    ZABCDEFGHIJKLMNOPQRSTUVWXY    

With {} :

0    ABCDEFGHIJKLMNOPQRSTUVWXYZ    
1    BCDEFGHIJKLMNOPQRSTUVWXYZA    
2    CDEFGHIJKLMNOPQRSTUVWXYZAB    
3    DEFGHIJKLMNOPQRSTUVWXYZABC    
4    EFGHIJKLMNOPQRSTUVWXYZABCD    
5    FGHIJKLMNOPQRSTUVWXYZABCDE    
6    GHIJKLMNOPQRSTUVWXYZABCDEF    
7    HIJKLMNOPQRSTUVWXYZABCDEFG    
8    IJKLMNOPQRSTUVWXYZABCDEFGH    
9    JKLMNOPQRSTUVWXYZABCDEFGHI    
10    KLMNOPQRSTUVWXYZABCDEFGHIJ    
11    LMNOPQRSTUVWXYZABCDEFGHIJK    
12    MNOPQRSTUVWXYZABCDEFGHIJKL    
13    NOPQRSTUVWXYZABCDEFGHIJKLM    
14    OPQRSTUVWXYZABCDEFGHIJKLMN    
15    PQRSTUVWXYZABCDEFGHIJKLMNO    
16    QRSTUVWXYZABCDEFGHIJKLMNOP    
17    RSTUVWXYZABCDEFGHIJKLMNOPQ    
18    STUVWXYZABCDEFGHIJKLMNOPQR    
19    TUVWXYZABCDEFGHIJKLMNOPQRS    
20    UVWXYZABCDEFGHIJKLMNOPQRST    
21    VWXYZABCDEFGHIJKLMNOPQRSTU    
22    WXYZABCDEFGHIJKLMNOPQRSTUV    
23    XYZABCDEFGHIJKLMNOPQRSTUVW    
24    YZABCDEFGHIJKLMNOPQRSTUVWX    
25    ZABCDEFGHIJKLMNOPQRSTUVWXY