第四章  4 程序控制结构——案例.ipynb

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    "### **示例 4-1**  输入若干个成绩,求所有成绩的平均分.每输入一个成绩后询问是否继续输入下一个成绩,回答yes则继续,回答no则停止"
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      "请输入一个成绩:99\n",
      "继续输入吗?(yes/no)yes\n",
      "请输入一个成绩:12\n",
      "继续输入吗?(yes/no)no\n",
      "55.5\n"
     ]
    }
   ],
   "source": [
    "numbers = []  #使用列表存放临时数据\n",
    "while True:\n",
    "    x = input('请输入一个成绩:')\n",
    "    try:  #异常处理\n",
    "        numbers.append(float(x))\n",
    "    except:\n",
    "        print('不是合法成绩')\n",
    "    while True:\n",
    "        flag = input('继续输入吗?(yes/no)')\n",
    "        if flag.lower() not in ('yes','no'):  #限定用户输入内容\n",
    "            print('只能输入yes或no')\n",
    "        else:\n",
    "            break\n",
    "    if flag.lower()=='no':\n",
    "        break\n",
    "print(sum(numbers)/len(numbers))"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### **示例 4-2** 编写程序,判断今天是今年的第几天"
   ]
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  {
   "cell_type": "code",
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     "name": "stdout",
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     "text": [
      "138\n"
     ]
    }
   ],
   "source": [
    "import time\n",
    "date = time.localtime()\n",
    "year,month,day = date[:3]\n",
    "day_month = [31,28,31,30,31,30,31,31,30,31,30,31]\n",
    "if year%400 == 0 or  (year%4 == 0 and year%100 != 0):\n",
    "    day_month[1] = 29\n",
    "if month == 1:\n",
    "    print(day)\n",
    "else:\n",
    "    print(sum(day_month[:month-1])+day)"
   ]
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   "cell_type": "markdown",
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   "source": [
    "- 标准库calendar提供了一些与日期操作有关的方法"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
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     "name": "stdout",
     "output_type": "stream",
     "text": [
      "                                  2019\n",
      "\n",
      "      January                   February                   March\n",
      "Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su\n",
      "    1  2  3  4  5  6                   1  2  3                   1  2  3\n",
      " 7  8  9 10 11 12 13       4  5  6  7  8  9 10       4  5  6  7  8  9 10\n",
      "14 15 16 17 18 19 20      11 12 13 14 15 16 17      11 12 13 14 15 16 17\n",
      "21 22 23 24 25 26 27      18 19 20 21 22 23 24      18 19 20 21 22 23 24\n",
      "28 29 30 31               25 26 27 28               25 26 27 28 29 30 31\n",
      "\n",
      "       April                      May                       June\n",
      "Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su\n",
      " 1  2  3  4  5  6  7             1  2  3  4  5                      1  2\n",
      " 8  9 10 11 12 13 14       6  7  8  9 10 11 12       3  4  5  6  7  8  9\n",
      "15 16 17 18 19 20 21      13 14 15 16 17 18 19      10 11 12 13 14 15 16\n",
      "22 23 24 25 26 27 28      20 21 22 23 24 25 26      17 18 19 20 21 22 23\n",
      "29 30                     27 28 29 30 31            24 25 26 27 28 29 30\n",
      "\n",
      "        July                     August                  September\n",
      "Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su\n",
      " 1  2  3  4  5  6  7                1  2  3  4                         1\n",
      " 8  9 10 11 12 13 14       5  6  7  8  9 10 11       2  3  4  5  6  7  8\n",
      "15 16 17 18 19 20 21      12 13 14 15 16 17 18       9 10 11 12 13 14 15\n",
      "22 23 24 25 26 27 28      19 20 21 22 23 24 25      16 17 18 19 20 21 22\n",
      "29 30 31                  26 27 28 29 30 31         23 24 25 26 27 28 29\n",
      "                                                    30\n",
      "\n",
      "      October                   November                  December\n",
      "Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su      Mo Tu We Th Fr Sa Su\n",
      "    1  2  3  4  5  6                   1  2  3                         1\n",
      " 7  8  9 10 11 12 13       4  5  6  7  8  9 10       2  3  4  5  6  7  8\n",
      "14 15 16 17 18 19 20      11 12 13 14 15 16 17       9 10 11 12 13 14 15\n",
      "21 22 23 24 25 26 27      18 19 20 21 22 23 24      16 17 18 19 20 21 22\n",
      "28 29 30 31               25 26 27 28 29 30         23 24 25 26 27 28 29\n",
      "                                                    30 31\n",
      "\n",
      "      May 2019\n",
      "Mo Tu We Th Fr Sa Su\n",
      "       1  2  3  4  5\n",
      " 6  7  8  9 10 11 12\n",
      "13 14 15 16 17 18 19\n",
      "20 21 22 23 24 25 26\n",
      "27 28 29 30 31\n",
      "\n",
      "False\n",
      "5\n"
     ]
    }
   ],
   "source": [
    "import calendar\n",
    "print(calendar.calendar(2019))  #查看2019年的日历表\n",
    "print(calendar.month(2019,5))  #查看2019年5月的日历表\n",
    "print(calendar.isleap(2019))  #判断是否为闰年\n",
    "print(calendar.weekday(2019,5,18))  #查看指定日期是周几"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### **示例 4-3** 编写代码,输出由星号*组成的菱形图案,并且可以灵活控制图案的大小"
   ]
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     "text": [
      "                  \n",
      "        *         \n",
      "       * *        \n",
      "      * * *       \n",
      "     * * * *      \n",
      "    * * * * *     \n",
      "   * * * * * *    \n",
      "    * * * * *     \n",
      "     * * * *      \n",
      "      * * *       \n",
      "       * *        \n",
      "        *         \n",
      "None\n"
     ]
    }
   ],
   "source": [
    "def main(n):\n",
    "    for i in range(n):\n",
    "        print(('* '*i).center(n*3))  #center中的参数为字符串的总宽度\n",
    "    for i in range(n,0,-1):\n",
    "        print(('* '*i).center(n*3))\n",
    "print(main(6))"
   ]
  }
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