list_index.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "python list 用[]定义"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [],
   "source": [
    "s=[0,1,2,3,4,5,6,7,8,9,10]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "s的长度是11"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "11"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "len(s)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "python list可以用[]使用指针,假设len()=N,可以使用[-n]表示第[N-n]个位置（第n个位置是第n+1个元素）"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "5\n",
      "5\n"
     ]
    }
   ],
   "source": [
    "print(s[5])\n",
    "print(s[-6])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "使用[x:y]表示从第x（含）个位置到第y（不含）的元素，其共有x-y个元素"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[3, 4, 5, 6]\n",
      "4\n"
     ]
    }
   ],
   "source": [
    "print(s[3:7])\n",
    "print(len(s[3:7]))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "\n",
    "[x:y]中的x或y为空则表示从头或到尾的元素"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[0, 1, 2, 3]\n",
      "[4, 5, 6, 7, 8, 9, 10]\n",
      "[0, 1, 2, 3]\n",
      "[4, 5, 6, 7, 8, 9, 10]\n"
     ]
    }
   ],
   "source": [
    "print(s[:4])\n",
    "print(s[4:])\n",
    "print(s[:-7])\n",
    "print(s[-7:])"
   ]
  }
 ],
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