jeapedu 28 字符串切片

# 字符串是有序集合
s = "hello the cruel world"
#    012345678901234567890
print(s[20], s[4])
print(s[6], s[7], s[8])
print(s[6] + s[7] + s[8])
t = s[6] + s[7] + s[8]
print(t)
# 数字累加求和
k = 1
s = 0
s = s + 1
s = s + 2
s = s + 3
s = 0
while k < 10:
s += k
k += 1
print(s)

s = "hello the cruel world"
#    012345678901234567890
#    ----------|----|-----
# slice stringName[start : end]
print(s[10 : 15], s[6 : 9], s[: 5], s[16:len(s)], "/", s[:])
t = ""
t = t + s[0]
t = t + s[1]
t = t + s[2]
t = t + s[3]
t = t + s[4]
print(t)

t = "welcom to "
i = 6
while i < len(s):
t += s[i]
i += 1
print(t)
print("======")
# find sub in s
s = "hello the cruel world" # length is 21, 0~20
#    012345678901234567890
sub =          "rue"        # length is 3,  0~2
i = 0
while i < len(s) - len(sub) + 1: # 21-3=18, 最后一个循环从第19个数开始，即上界是0～20的第19个数(18)的后一位(19)。从0开始，18是第19个数，上界是后一个19。
j = 1 # j应从1开始，从0开始，s[i:i+0]没有意义。
while j < len(sub) + 1: # j代表s[start:end]的end，s[]为左闭右开区间，s[0:3]是0 1 2，不含3，三位。字符串上界为3，循环要有3，0 1 2 3。
if s[i:i+j] == sub:
print(i, s[i:i+j])
#print(i, s[i:i+j])
j += 1
i += 1