python3 string comparison like '9' < '10'

Question

I read this question String comparison technique used by Python.

But, i don't know exactly why the comparison '9' < '10' is False. Did this happen because '9' is bigger than '1'? because python's string comparison is lexicographic?

Answer 1

Python grabs the first character in the strings and compares them. In this case it starts by comparing if 9 is less than 1. Since it's not, False is returned. Comparisons are done using the character codes. (To save you some time looking it up, 1-9 are indeed in numerical order. Something to be careful about is the capital letters are before the lowercase ones, so 'B' < 'a' returns True.)

If the comparison were equal, it would move on to the next character and so on.

You can use isnumeric to check if you're comparing 2 numbers, and if you are then change the strings to numbers before comparing.

if a.isnumeric() and b.isnumeric():
    if float(a) < float(b):

Answer 2

In lexicographic order "10" comes before "9" that is why it is returning False. If you did

"10" < "9"

You would get True because the string "10" comes before the string "9".