Getting an error when printing the middle character of a string

Question

When trying to print the middle character of a string using the following code:

def mid(a):
    return a[(len(a) + 1) / 2]
    
print(mid("abc"))

I get the error:

TypeError: string indices must be integers

Changing it to:

 def mid(a):
    return a[(len(a) - 1) // 2 : (len(a) + 2) // 2]
    
print(mid("abc"))

outputs:

Why does directly grabbing the middle value return the TypeError, but grabbing the 0th value and then the middle value actually work?

Hint: What's the difference between `//` and `/` in Python 3? — General Grievance, Feb 18 '21 at 16:55
@Calculuswhiz thanks! I had not realized that by doing a / 2 division the 2.0 i was getting was still a float, thanks for pointing out the subtle difference :) — Leprekus, Feb 18 '21 at 17:10

score 2 · Accepted Answer · answered Feb 18 '21 at 16:54

2

Division returns a float. You want floor division.

>>> 4/2
2.0
>>> 4//2
2

It seems like you fixed this without noticing in your changed code.

answered Feb 18 '21 at 16:54

wjandrea

1 Answers1