Characters are numbers underneath as well. A character is a code point, and text is a list of them, which is why text can be measured, indexed, and compared at all.
About 2 min of reading
Index, slice, and compare text by position.
Get the code point of a letter and back.
Before you run it, say out loud what it will print. Then open the answer.
Measure text and pick ends by position.
Before you run it, say out loud what it will print. Then open the answer.
Take a middle range. The end index is not included.
Before you run it, say out loud what it will print. Then open the answer.
Compare two words and two cases. Case changes the order.
Before you run it, say out loud what it will print. Then open the answer.
Read the first example one line at a time. A line that prints shows what appears on screen; the rest set things up quietly.
A file, a web page, and a keyboard all carry text as bytes. The encoding says which bytes mean which code point. Two tools that disagree about the encoding turn the same bytes into different text, which is the cause of the garbled characters you sometimes see.
A slice or an index works on positions, so it does not care what the text says. That is what makes the same trimming code work on any input, and it is also why a position count has to start at zero rather than one.
print(ord("A"))
print(chr(65))ord gives the code point of a character, chr goes back. The pair is the bridge between a character and the number stored for it, and both directions are exact.
word = "owlww"
print(len(word))
print(word[0])
print(word[-1])len counts the code points. Brackets pick a position, counting from zero at the front, and minus one counts back from the end. Positions are the reason an off-by-one bug exists.
word = "owlww"
print(word[1:4])
print(word[:2])A slice takes from the first index up to but not including the second. Leaving an end off takes everything to that edge. Slices never fail on a range that is too big, which makes them safe for trimming.
print("apple" < "banana")
print("Zoo" < "apple")Text compares code point by code point, so uppercase letters sort before lowercase. That is why a list of names can come out in an order that looks wrong but is perfectly consistent.
Each one is defined here on this site. Open the entry for the full definition and the other words it points at.