Python计算机二级考试全面教学文档<\/h1>

考试概述<\/h2>

考试方式<\/strong>: 上机考试<\/li>
考试时长<\/strong>: 120分钟<\/li>
满分<\/strong>: 100分<\/li>

题型及分值<\/strong>:

单项选择题40分(含公共基础知识部分10分)<\/li>
操作题60分(包括基本编程题和综合编程题)<\/li> <\/ul> <\/li>
考试环境<\/strong>:

Windows 7操作系统<\/li>
Python 3.4.2至Python 3.5.3版本<\/li>
IDLE开发环境<\/li> <\/ul> <\/li> <\/ul>
一、Python语言基本语法元素<\/h2>
1. 程序的基本语法元素<\/h3>

格式框架<\/strong>: Python使用缩进表示代码块，通常4个空格为一个缩进层级<\/li>
缩进<\/strong>: 同一代码块的语句必须有相同的缩进量<\/li>
注释<\/strong>:

单行注释: # 注释内容<\/code><\/li>
多行注释: 使用三引号 '''注释内容'''<\/code> 或 """注释内容"""<\/code><\/li> <\/ul> <\/li>
变量<\/strong>: 无需声明类型，直接赋值即可创建<\/li>
命名规则<\/strong>: 由字母、数字和下划线组成<\/li> 不能以数字开头<\/li> 区分大小写<\/li> 不能使用保留字<\/li> <\/ul> <\/li> 保留字<\/strong>: 如if<\/code>, else<\/code>, for<\/code>, while<\/code>, def<\/code>, class<\/code>等<\/li> 数据类型<\/strong>: 包括数字、字符串、列表、元组、字典等<\/li> 赋值语句<\/strong>: 变量名 = 值<\/code><\/li> 引用<\/strong>: 变量是对值的引用<\/li> <\/ul> 2. 基本输入输出函数<\/h3> input([prompt])<\/code>: 获取用户输入，返回字符串 name =<\/span> input("请输入您的名字: "<\/span>) <\/span><\/span><\/code><\/pre><\/li> eval(expression)<\/code>: 计算字符串表达式并返回结果 result =<\/span> eval("3 + 5"<\/span>) # 返回8<\/span> <\/span><\/span><\/code><\/pre><\/li> print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)<\/code>: 输出内容 print("Hello"<\/span>, "World"<\/span>, sep=<\/span>"-"<\/span>, end=<\/span>"!"<\/span>) <\/span><\/span><\/code><\/pre><\/li> <\/ul> 3. 源程序的书写风格<\/h3> PEP 8编码规范<\/li> 每行不超过79个字符<\/li> 适当使用空行分隔函数和类<\/li> 运算符两侧和逗号后加空格<\/li> <\/ul> 4. Python语言特点<\/h3> 解释型语言<\/li> 动态类型<\/li> 面向对象<\/li> 丰富的标准库<\/li> 跨平台<\/li> 可扩展性<\/li> <\/ul> 二、基本数据类型<\/h2> 1. 数字类型<\/h3> 整数类型(int)<\/strong>: 如10<\/code>, -5<\/code>, 0<\/code><\/li> 浮点数类型(float)<\/strong>: 如3.14<\/code>, -0.001<\/code>, 2.0<\/code><\/li> 复数类型(complex)<\/strong>: 如3+4j<\/code>, -2j<\/code><\/li> <\/ul> 2. 数字类型的运算<\/h3> 数值运算操作符<\/strong>: 算术运算符: +<\/code>, -<\/code>, *<\/code>, \/<\/code>, \/\/<\/code>(整除), %<\/code>(取余), **<\/code>(幂运算)<\/li> 增强赋值运算符: +=<\/code>, -=<\/code>, *=<\/code>, \/=<\/code>, \/\/=<\/code>, %=<\/code>, **=<\/code><\/li> <\/ul> <\/li> 数值运算函数<\/strong>: abs(x)<\/code>: 绝对值<\/li> divmod(x, y)<\/code>: 返回商和余数<\/li> pow(x, y[, z])<\/code>: 幂运算<\/li> round(x[, n])<\/code>: 四舍五入<\/li> max(x1, x2,...)<\/code>: 最大值<\/li> min(x1, x2,...)<\/code>: 最小值<\/li> <\/ul> <\/li> <\/ul> 3. 字符串类型及格式化<\/h3> 字符串表示<\/strong>: 单引号' '<\/code>、双引号" "<\/code>或三引号''' '''<\/code>\/""" """<\/code><\/li> 索引<\/strong>: str[index]<\/code>，索引从0开始<\/li> 切片<\/strong>: str[start:end:step]<\/code> s =<\/span> "Python"<\/span> <\/span><\/span>print(s[1<\/span>:4<\/span>]) # 输出"yth"<\/span> <\/span><\/span><\/code><\/pre><\/li> format()格式化<\/strong>: "<\/span>{}<\/span> is <\/span>{}<\/span> years old"<\/span>.<\/span>format("Tom"<\/span>, 20<\/span>) <\/span><\/span>"<\/span>{1}<\/span> is <\/span>{0}<\/span> years old"<\/span>.<\/span>format(20<\/span>, "Tom"<\/span>) <\/span><\/span>"<\/span>{name}<\/span> is <\/span>{age}<\/span> years old"<\/span>.<\/span>format(name=<\/span>"Tom"<\/span>, age=<\/span>20<\/span>) <\/span><\/span><\/code><\/pre><\/li> <\/ul> 4. 字符串类型的操作<\/h3> 字符串操作符<\/strong>: +<\/code>: 连接<\/li> *<\/code>: 重复<\/li> in<\/code>: 成员判断<\/li> <\/ul> <\/li> 字符串处理函数<\/strong>: len(str)<\/code>: 长度<\/li> str(x)<\/code>: 转换为字符串<\/li> chr(x)<\/code>: Unicode编码转字符<\/li> ord(x)<\/code>: 字符转Unicode编码<\/li> hex(x)<\/code>: 整数转十六进制字符串<\/li> oct(x)<\/code>: 整数转八进制字符串<\/li> <\/ul> <\/li> 字符串处理方法<\/strong>: str.lower()<\/code>: 转小写<\/li> str.upper()<\/code>: 转大写<\/li> str.split(sep=None)<\/code>: 分割字符串<\/li> str.count(sub)<\/code>: 统计子串出现次数<\/li> str.replace(old, new)<\/code>: 替换<\/li> str.center(width[, fillchar])<\/code>: 居中<\/li> str.strip([chars])<\/code>: 去除两端字符<\/li> str.join(iterable)<\/code>: 连接序列元素<\/li> <\/ul> <\/li> <\/ul> 5. 类型判断和类型间转换<\/h3> 类型判断<\/strong>: type(x)<\/code>: 返回类型<\/li> isinstance(x, type)<\/code>: 判断类型<\/li> <\/ul> <\/li> 类型转换<\/strong>: int(x)<\/code>: 转为整数<\/li> float(x)<\/code>: 转为浮点数<\/li> str(x)<\/code>: 转为字符串<\/li> list(x)<\/code>: 转为列表<\/li> tuple(x)<\/code>: 转为元组<\/li> set(x)<\/code>: 转为集合<\/li> dict(x)<\/code>: 转为字典<\/li> <\/ul> <\/li> <\/ul> 三、程序的控制结构<\/h2> 1. 程序的三种控制结构<\/h3> 顺序结构<\/li> 分支结构<\/li> 循环结构<\/li> <\/ul> 2. 程序的分支结构<\/h3> 单分支结构<\/strong>: if<\/span> 条件: <\/span><\/span> 语句块 <\/span><\/span><\/code><\/pre><\/li> 二分支结构<\/strong>: if<\/span> 条件: <\/span><\/span> 语句块1 <\/span><\/span>else<\/span>: <\/span><\/span> 语句块2 <\/span><\/span><\/code><\/pre><\/li> 多分支结构<\/strong>: if<\/span> 条件1: <\/span><\/span> 语句块1 <\/span><\/span>elif<\/span> 条件2: <\/span><\/span> 语句块2 <\/span><\/span>...<\/span> <\/span><\/span>else<\/span>: <\/span><\/span> 语句块n <\/span><\/span><\/code><\/pre><\/li> <\/ul> 3. 程序的循环结构<\/h3> 遍历循环(for)<\/strong>: for<\/span> 变量 in<\/span> 序列: <\/span><\/span> 语句块 <\/span><\/span><\/code><\/pre>示例: for<\/span> i in<\/span> range(5<\/span>): <\/span><\/span> print(i) <\/span><\/span><\/code><\/pre><\/li> 无限循环(while)<\/strong>: while<\/span> 条件: <\/span><\/span> 语句块 <\/span><\/span><\/code><\/pre><\/li> 循环控制<\/strong>: break<\/code>: 跳出当前循环<\/li> continue<\/code>: 跳过本次循环剩余部分<\/li> else<\/code>: 循环正常结束后执行<\/li> <\/ul> <\/li> <\/ul> 4. 程序的异常处理<\/h3> try<\/span>: <\/span><\/span> 可能引发异常的代码 <\/span><\/span>except<\/span> 异常类型1: <\/span><\/span> 处理异常1的代码 <\/span><\/span>except<\/span> 异常类型2: <\/span><\/span> 处理异常2的代码 <\/span><\/span>...<\/span> <\/span><\/span>except<\/span>: <\/span><\/span> 处理其他异常的代码 <\/span><\/span>else<\/span>: <\/span><\/span> 没有异常时执行的代码 <\/span><\/span>finally<\/span>: <\/span><\/span> 无论是否发生异常都会执行的代码 <\/span><\/span><\/code><\/pre>四、函数和代码复用<\/h2> 1. 函数的定义和使用<\/h3> def<\/span> 函数名<\/span>(参数列表): <\/span><\/span> """文档字符串"""<\/span> <\/span><\/span> 函数体 <\/span><\/span> return<\/span> 返回值 <\/span><\/span><\/code><\/pre>2. 函数的参数传递<\/h3> 位置参数<\/strong>: 按位置顺序传递<\/li> 默认参数<\/strong>: 定义时指定默认值<\/li> 可变参数<\/strong>: *args<\/code>: 接收任意数量的位置参数，打包为元组<\/li> **kwargs<\/code>: 接收任意数量的关键字参数，打包为字典<\/li> <\/ul> <\/li> 参数名称传递<\/strong>: 调用时指定参数名<\/li> 返回值<\/strong>: 可以返回多个值(实际上是返回一个元组)<\/li> <\/ul> 3. 变量的作用域<\/h3> 局部变量<\/strong>: 函数内部定义的变量<\/li> 全局变量<\/strong>: 函数外部定义的变量<\/li> global<\/code>关键字: 在函数内部声明使用全局变量<\/li> nonlocal<\/code>关键字: 在嵌套函数中声明使用外层函数的变量<\/li> <\/ul> 五、组合数据类型<\/h2> 1. 组合数据类型的基本概念<\/h3> 序列类型: 字符串、列表、元组<\/li> 集合类型: 集合<\/li> 映射类型: 字典<\/li> <\/ul> 2. 列表类型<\/h3> 定义<\/strong>: [元素1, 元素2, ...]<\/code> 或 list(可迭代对象)<\/code><\/li> 索引<\/strong>: 从0开始，支持负数索引<\/li> 切片<\/strong>: list[start:end:step]<\/code><\/li> 操作函数<\/strong>: len(list)<\/code>: 长度<\/li> max(list)<\/code>: 最大值<\/li> min(list)<\/code>: 最小值<\/li> sum(list)<\/code>: 求和(仅数字)<\/li> sorted(list)<\/code>: 排序<\/li> <\/ul> <\/li> 操作方法<\/strong>: list.append(x)<\/code>: 追加元素<\/li> list.extend(iterable)<\/code>: 扩展列表<\/li> list.insert(i, x)<\/code>: 插入元素<\/li> list.remove(x)<\/code>: 删除第一个匹配项<\/li> list.pop([i])<\/code>: 删除并返回指定位置元素<\/li> list.clear()<\/code>: 清空列表<\/li> list.index(x)<\/code>: 返回第一个匹配项的索引<\/li> list.count(x)<\/code>: 统计元素出现次数<\/li> list.sort(key=None, reverse=False)<\/code>: 排序<\/li> list.reverse()<\/code>: 反转<\/li> list.copy()<\/code>: 浅拷贝<\/li> <\/ul> <\/li> <\/ul> 3. 字典类型<\/h3> 定义<\/strong>: {键1:值1, 键2:值2, ...}<\/code> 或 dict(键=值, ...)<\/code><\/li> 索引<\/strong>: dict[key]<\/code> 或 dict.get(key[, default])<\/code><\/li> 操作函数<\/strong>: len(dict)<\/code>: 键值对数量<\/li> str(dict)<\/code>: 字符串表示<\/li> <\/ul> <\/li> 操作方法<\/strong>: dict.clear()<\/code>: 清空字典<\/li> dict.copy()<\/code>: 浅拷贝<\/li> dict.fromkeys(seq[, value])<\/code>: 创建新字典<\/li> dict.get(key[, default])<\/code>: 获取值<\/li> dict.items()<\/code>: 返回键值对视图<\/li> dict.keys()<\/code>: 返回键视图<\/li> dict.values()<\/code>: 返回值视图<\/li> dict.pop(key[, default])<\/code>: 删除并返回值<\/li> dict.popitem()<\/code>: 删除并返回最后一对键值<\/li> dict.setdefault(key[, default])<\/code>: 设置默认值<\/li> dict.update([other])<\/code>: 更新字典<\/li> <\/ul> <\/li> <\/ul> 六、文件和数据格式化<\/h2> 1. 文件的使用<\/h3> 打开文件<\/strong>:<\/p> file =<\/span> open(filename, mode=<\/span>'r'<\/span>, encoding=<\/span>None<\/span>) <\/span><\/span><\/code><\/pre>模式:<\/p> 'r'<\/code>: 读取(默认)<\/li> 'w'<\/code>: 写入(覆盖)<\/li> 'x'<\/code>: 独占创建<\/li> 'a'<\/code>: 追加<\/li> 'b'<\/code>: 二进制模式<\/li> 't'<\/code>: 文本模式(默认)<\/li> '+'<\/code>: 更新(读写)<\/li> <\/ul> <\/li> 读取文件<\/strong>:<\/p> file.read([size])<\/code>: 读取指定字节数<\/li> file.readline()<\/code>: 读取一行<\/li> file.readlines()<\/code>: 读取所有行<\/li> <\/ul> <\/li> 写入文件<\/strong>:<\/p> file.write(str)<\/code>: 写入字符串<\/li> file.writelines(sequence)<\/code>: 写入字符串序列<\/li> <\/ul> <\/li> 关闭文件<\/strong>:<\/p> file.<\/span>close() <\/span><\/span><\/code><\/pre>或使用with<\/code>语句自动关闭:<\/p> with<\/span> open(filename) as<\/span> file: <\/span><\/span> # 操作文件<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> 2. 数据组织的维度<\/h3> 一维数据<\/strong>: 线性结构，如列表、集合<\/li> 二维数据<\/strong>: 表格结构，如嵌套列表<\/li> <\/ul> 3. 一维数据的处理<\/h3> 表示<\/strong>: 列表、集合<\/li> 存储<\/strong>: 按行或按列存储<\/li> 处理<\/strong>: 遍历、切片、统计等<\/li> <\/ul> 4. 二维数据的处理<\/h3> 表示<\/strong>: 列表的列表 data =<\/span> [[1<\/span>, 2<\/span>, 3<\/span>], [4<\/span>, 5<\/span>, 6<\/span>], [7<\/span>, 8<\/span>, 9<\/span>]] <\/span><\/span><\/code><\/pre><\/li> 存储<\/strong>: CSV格式<\/li> 处理<\/strong>: 双重循环遍历<\/li> <\/ul> 5. CSV格式读写<\/h3> 读取CSV<\/strong>: import<\/span> csv <\/span><\/span>with<\/span> open('data.csv'<\/span>, 'r'<\/span>) as<\/span> file: <\/span><\/span> reader =<\/span> csv.<\/span>reader(file) <\/span><\/span> for<\/span> row in<\/span> reader: <\/span><\/span> print(row) <\/span><\/span><\/code><\/pre><\/li> 写入CSV<\/strong>: import<\/span> csv <\/span><\/span>data =<\/span> [['Name'<\/span>, 'Age'<\/span>], ['Tom'<\/span>, 20<\/span>], ['Jerry'<\/span>, 18<\/span>]] <\/span><\/span>with<\/span> open('output.csv'<\/span>, 'w'<\/span>, newline=<\/span>''<\/span>) as<\/span> file: <\/span><\/span> writer =<\/span> csv.<\/span>writer(file) <\/span><\/span> writer.<\/span>writerows(data) <\/span><\/span><\/code><\/pre><\/li> <\/ul> 七、Python计算生态<\/h2> 1. 标准库<\/h3> turtle库(必选)<\/strong>: 绘图 import<\/span> turtle <\/span><\/span>t =<\/span> turtle.<\/span>Turtle() <\/span><\/span>t.<\/span>forward(100<\/span>) <\/span><\/span><\/code><\/pre><\/li> random库(必选)<\/strong>: 随机数 import<\/span> random <\/span><\/span>random.<\/span>random() # [0.0, 1.0)<\/span> <\/span><\/span>random.<\/span>randint(a, b) # [a, b]<\/span> <\/span><\/span>random.<\/span>choice(seq) # 随机选择<\/span> <\/span><\/span>random.<\/span>shuffle(seq) # 随机打乱<\/span> <\/span><\/span><\/code><\/pre><\/li> time库(可选)<\/strong>: 时间处理 import<\/span> time <\/span><\/span>time.<\/span>time() # 时间戳<\/span> <\/span><\/span>time.<\/span>sleep(secs) # 暂停<\/span> <\/span><\/span>time.<\/span>strftime(format[, t]) # 格式化时间<\/span> <\/span><\/span><\/code><\/pre><\/li> <\/ul> 2. 基本的Python内置函数<\/h3> abs()<\/code>, all()<\/code>, any()<\/code>, bin()<\/code>, bool()<\/code>, chr()<\/code>, dict()<\/code>, dir()<\/code>, enumerate()<\/code>, eval()<\/code>, filter()<\/code>, float()<\/code>, format()<\/code>, help()<\/code>, hex()<\/code>, id()<\/code>, input()<\/code>, int()<\/code>, isinstance()<\/code>, iter()<\/code>, len()<\/code>, list()<\/code>, map()<\/code>, max()<\/code>, min()<\/code>, next()<\/code>, oct()<\/code>, open()<\/code>, ord()<\/code>, pow()<\/code>, print()<\/code>, range()<\/code>, reversed()<\/code>, round()<\/code>, set()<\/code>, sorted()<\/code>, str()<\/code>, sum()<\/code>, tuple()<\/code>, type()<\/code>, zip()<\/code><\/li> <\/ul> 3. 第三方库的获取和安装<\/h3> 使用pip安装: pip install 包名 <\/span><\/span><\/code><\/pre><\/li> 指定版本: pip install 包名==<\/span>版本号 <\/span><\/span><\/code><\/pre><\/li> 升级: pip install --upgrade 包名 <\/span><\/span><\/code><\/pre><\/li> <\/ul> 4. 必选第三方库<\/h3> PyInstaller库<\/strong>: 打包Python脚本为可执行文件 pyinstaller -F script.py <\/span><\/span><\/code><\/pre><\/li> jieba库<\/strong>: 中文分词 import<\/span> jieba <\/span><\/span>seg_list =<\/span> jieba.<\/span>cut("我爱自然语言处理"<\/span>, cut_all=<\/span>True<\/span>) <\/span><\/span>print(" "<\/span>.<\/span>join(seg_list)) <\/span><\/span><\/code><\/pre><\/li> <\/ul> 5. 可选第三方库<\/h3> wordcloud库<\/strong>: 词云生成 from<\/span> wordcloud import<\/span> WordCloud <\/span><\/span>wc =<\/span> WordCloud().<\/span>generate(text) <\/span><\/span>wc.<\/span>to_file("wordcloud.png"<\/span>) <\/span><\/span><\/code><\/pre><\/li> <\/ul> 6. 更广泛的Python计算生态<\/h3> 网络爬虫<\/strong>: Scrapy, BeautifulSoup, Requests<\/li> 数据分析<\/strong>: NumPy, Pandas, SciPy<\/li> 文本处理<\/strong>: NLTK, TextBlob<\/li> 数据可视化<\/strong>: Matplotlib, Seaborn, Plotly<\/li> 用户图形界面<\/strong>: PyQt, Tkinter, wxPython<\/li> 机器学习<\/strong>: Scikit-learn, TensorFlow, PyTorch<\/li> Web开发<\/strong>: Django, Flask, Tornado<\/li> 游戏开发<\/strong>: Pygame, Panda3D<\/li> <\/ul> 备考建议<\/h2> 基础语法<\/strong>:<\/p> 熟练掌握基本语法元素<\/li> 理解Python的缩进规则<\/li> 熟练使用基本数据类型和操作符<\/li> <\/ul> <\/li> 控制结构<\/strong>:<\/p> 掌握分支和循环的各种形式<\/li> 理解异常处理机制<\/li> 熟练使用break和continue<\/li> <\/ul> <\/li> 函数和代码复用<\/strong>:<\/p> 熟练定义和调用函数<\/li> 理解参数传递的各种方式<\/li> 掌握变量的作用域规则<\/li> <\/ul> <\/li> 组合数据类型<\/strong>:<\/p> 熟练使用列表和字典<\/li> 理解序列操作和字典操作<\/li> 掌握常用方法和函数<\/li> <\/ul> <\/li> 文件操作<\/strong>:<\/p> 熟练读写文件<\/li> 理解CSV格式<\/li> 掌握一维和二维数据处理<\/li> <\/ul> <\/li> 标准库和第三方库<\/strong>:<\/p> 重点掌握turtle、random库<\/li> 理解PyInstaller和jieba库的使用<\/li> 了解其他常用库的基本功能<\/li> <\/ul> <\/li> 实践练习<\/strong>:<\/p> 多做编程题，特别是操作题<\/li> 熟悉IDLE开发环境<\/li> 练习在规定时间内完成题目<\/li> <\/ul> <\/li> 模拟考试<\/strong>:<\/p> 进行全真模拟，掌握时间分配<\/li> 分析错题，查漏补缺<\/li> 重点复习薄弱环节<\/li> <\/ul> <\/li> <\/ol>