【Python】

 

 

1. 基础语法示例

 

```python

# 变量和数据类型

name = "Alice"

age = 25

height = 1.65

is_student = True

 

# 列表操作

fruits = ["apple", "banana", "orange"]

fruits.append("grape")

fruits.remove("banana")

 

# 字典操作

person = {

    "name": "Bob",

    "age": 30,

    "city": "New York"

}

 

# 条件判断

if age >= 18:

    print(f"{name}是成年人")

else:

    print(f"{name}是未成年人")

 

# 循环

for fruit in fruits:

    print(f"我喜欢吃{fruit}")

 

for i in range(5):

    print(f"这是第{i+1}次循环")

```

 

2. 函数定义和使用

 

```python

def calculate_bmi(weight, height):

    """计算BMI指数"""

    bmi = weight / (height ** 2)

    return bmi

 

def greet(name, greeting="Hello"):

    """打招呼函数"""

    return f"{greeting}, {name}!"

 

# 使用函数

bmi = calculate_bmi(70, 1.75)

print(f"BMI指数: {bmi:.2f}")

 

message = greet("Alice")

print(message)

```

 

3. 文件操作

 

```python

# 写入文件

with open("example.txt", "w", encoding="utf-8") as file:

    file.write("Hello, World!\n")

    file.write("这是第二行内容\n")

 

# 读取文件

with open("example.txt", "r", encoding="utf-8") as file:

    content = file.read()

    print("文件内容:")

    print(content)

 

# 逐行读取

with open("example.txt", "r", encoding="utf-8") as file:

    lines = file.readlines()

    for line_num, line in enumerate(lines, 1):

        print(f"第{line_num}行: {line.strip()}")

```

 

4. 数据处理示例

 

```python

import pandas as pd

 

# 创建数据

data = {

    '姓名': ['张三', '李四', '王五', '赵六'],

    '年龄': [25, 30, 35, 28],

    '城市': ['北京', '上海', '广州', '深圳'],

    '工资': [5000, 7000, 6000, 8000]

}

 

df = pd.DataFrame(data)

 

# 基本数据分析

print("数据概览:")

print(df.head())

 

print("\n基本统计信息:")

print(df.describe())

 

print("\n按城市分组统计平均工资:")

city_salary = df.groupby('城市')['工资'].mean()

print(city_salary)

```

 

5. 网络请求示例

 

```python

import requests

import json

 

def get_weather(city):

    """获取天气信息（示例）"""

    # 这里使用模拟数据，实际使用时需要真实的API

    weather_data = {

        "北京": {"temperature": 25, "condition": "晴"},

        "上海": {"temperature": 28, "condition": "多云"},

        "广州": {"temperature": 32, "condition": "雨"}

    }

    

    return weather_data.get(city, {"error": "城市不存在"})

 

# 使用示例

city = "北京"

weather = get_weather(city)

print(f"{city}的天气: {weather}")

 

# 实际的API请求示例（需要安装requests库）

try:

    response = requests.get('https://api.github.com/users/octocat')

    if response.status_code == 200:

        user_data = response.json()

        print(f"用户名: {user_data['login']}")

        print(f"主页: {user_data['html_url']}")

except requests.exceptions.RequestException as e:

    print(f"请求失败: {e}")

```

 

6. 面向对象编程

 

```python

class Student:

    def __init__(self, name, age, major):

        self.name = name

        self.age = age

        self.major = major

        self.grades = []

    

    def add_grade(self, grade):

        self.grades.append(grade)

    

    def get_average(self):

        if not self.grades:

            return 0

        return sum(self.grades) / len(self.grades)

    

    def display_info(self):

        print(f"学生: {self.name}")

        print(f"年龄: {self.age}")

        print(f"专业: {self.major}")

        print(f"平均分: {self.get_average():.2f}")

 

# 使用类

student1 = Student("张三", 20, "计算机科学")

student1.add_grade(85)

student1.add_grade(92)

student1.add_grade(78)

 

student1.display_info()

```

 

7. 错误处理

 

```python

def safe_divide(a, b):

    """安全的除法运算"""

    try:

        result = a / b

    except ZeroDivisionError:

        print("错误: 除数不能为零!")

        return None

    except TypeError:

        print("错误: 请输入数字!")

        return None

    else:

        return result

    finally:

        print("除法运算完成")

 

# 测试错误处理

print(safe_divide(10, 2)) # 正常情况

print(safe_divide(10, 0)) # 除零错误

print(safe_divide(10, "2")) # 类型错误

```

 

8. 列表推导式和生成器

 

```python

# 列表推导式

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

 

# 筛选偶数

even_numbers = [x for x in numbers if x % 2 == 0]

print(f"偶数: {even_numbers}")

 

# 平方数

squares = [x**2 for x in numbers]

print(f"平方数: {squares}")

 

# 生成器表达式

even_squares = (x**2 for x in numbers if x % 2 == 0)

print("生成器结果:")

for num in even_squares:

    print(num, end=" ")

```

 

这些示例涵盖了Python编程的多个重要方面。