在 Python 变量位置枚举

Question

i'd like to know: what's the difference between these two:

return "-".join([c.upper() + c.lower() * i for i,c in enumerate(txt)])
return "-".join([c.upper() + c.lower() * i for c,i in enumerate(txt)])

I just changed the 'i' with the 'c' and the whole code doesn't work. Is there a simple explanation?

Answer 1

Yes. enumerate() yields pairs of (index, item) from a given iterable.

For a string "hello" , it would return (formatted as a list)

[
  (0, 'h'),
  (1, 'e'),
  (2, 'l'),
  (3, 'l'),
  (4, 'o'),
]

For the sake of simplicity, let's look at the first item only, (0, 'h') .

If you use i, c to unpack this, i 's value will be 0 , and c 's value will be 'h' , and c.lower() etc. makes sense, as does multiplication with the number i .

If you use c, i to unpack this, c 's value will be 0 , and i 's value will be 'h' , and c.lower() no longer exists since c is a number and i is a string.