python_today 11_8

@: python_today

1. 将百分数字符串转换为浮点数的方法(x = ’20%’)

1. eval(x.replace(‘%’, ‘/100.0’)
   注意:eval()是求值函数
2. float(x.strip(‘%’))/100
3. float(x[:-1])/100

2. list的常见用法

1. 改变list中某个item, 直接 list[3] = item, 就把原来的替换了
2. 插入list.insert(position, item)在position位置插入item,原位置item后移
3. list.append(list)
   list1 = [4] list2 = [2, 3]
   list1.append(list2)
   list1 = [4, [2,3]]
4. list.extend(list)
   list1 = [4] list2 = [2, 3]
   list1.extend(list2)
   list1 = [4, 2, 3]
5. 删除list元素的几种方法:
   li = [ 2, 3, 4, 5, 6, 7, 8, 9]

• li[3:] = []
• del(li[3:])
• pop(-1)
  delete the item and return it, could be of special use
• remove(9)