String : an ordered sequence of characters

6個規則:

1. string 代表 orderd 有順序的字串
   1. → 具有index(索引)和slicing (截切)的功能 可以利用index number 載切出需要要資訊
2. Indexing start from 0 !!

mystring = "Hello"

# ordered sequence 正序
print(mystring[0])
print(mystring[1])
print(mystring[2])
print(mystring[3])
print(mystring[4])
print(mystring[5])  # out of range

# reverse ordered sequence 正序
print(mystring[0])
print(mystring[-1])
print(mystring[-2])
print(mystring[-3])
print(mystring[-4])
print(mystring[-5])
print(mystring[-6])  # out of range

---------------------------------------

[Running] python -u "d:\\2022_python_全攻略\\13. String Indexing and Slicing"
H
e
l
l
o
Traceback (most recent call last):
  File "d:\\2022_python_\\u5168\\u653b\\u7565\\13. String Indexing and Slicing", line 9, in <module>
    print(mystring[5])  # out of range
IndexError: string index out of range

[Running] python -u "d:\\2022_python_全攻略\\13. String Indexing and Slicing"
H
o
l
l
e
H
Traceback (most recent call last):
  File "d:\\2022_python_\\u5168\\u653b\\u7565\\13. String Indexing and Slicing", line 18, in <module>
    print(mystring[-6])  # out of range
IndexError: string index out of range

Slicing

string [ start (inclusive), end(exclusive), stepsize(optional)]

= 從要切的開始位數(inclusive) 到最後位數+1(end exclusive) ，設定stepsize要多大