[py]字符串/列表

去除str首尾空格(切片)

## str长度 循环,判断
### [:i]  [i:]  记录位置点

## 方法1
def trim2(s):
    s2 = ""
    start = 0
    end = 0
    # 找出第一个不为空的项的索引
    for i in range(len(s)):
        if s[:i] == (i + 1) * " " or s[:i] == (i + 1) * "":
            pass
        else:
            start = i
            break
    # 找出最后一个不为空的项的索引
    for i in range(len(s)):
        if s[i:] == (len(s) - i) * " ":
            pass
        else:
            end = i
    print(s[start:end + 1])
    return (s[start:end + 1])

trim2(" mao tai")


## 第二种方法
def trim3(s):
    while s[:1] == ' ':
        s = s[1:]
    print(s)
    while s[-1:]==' ':
        s = s[:-1]

trim3("  maotai3  s  ")