软考中级-软件设计师 Python篇

文章目录

Python 基础语法

x = 10       # 整数
y = 3.14     # 浮点数
z = "Hello"  # 字符串
a = True     # 布尔值

age = 18
if age >= 18:
    print("成人")
else:
    print("未成年")

for i in range(5):
    print(i)  # 输出 0 1 2 3 4

count = 0
while count < 5:
    print(count)
    count += 1

Python 数据结构

# 初始化列表
fruits = ["apple", "banana", "cherry"]

# 添加元素
fruits.append("orange")           # 添加到末尾
fruits.insert(1, "mango")         # 插入到指定位置

# 删除元素
fruits.remove("banana")           # 按值删除
del fruits[2]                     # 按索引删除
popped_item = fruits.pop()        # 删除最后一个元素并返回

# 查找元素
index = fruits.index("apple")     # 查找元素的索引
is_present = "cherry" in fruits   # 检查是否存在

# 输出列表
print(fruits)      # 示例输出: ['apple', 'mango', 'orange']

# 创建元组
person = ("Alice", 25, "Engineer")

# 访问元素
name = person[0]       # 读取第一个元素
age = person[1]        # 读取第二个元素

# 元组不可变，因此不能直接修改，但可以重新赋值
# person[1] = 26       # 错误：元组元素不可修改

# 可以通过拼接创建新的元组
updated_person = person[:1] + (26,) + person[2:]  # 更新年龄
print(updated_person)   # 输出: ('Alice', 26, 'Engineer')

# 元组解包
name, age, profession = person

# 查找元素
index = person.index("Engineer")  # 查找元素索引
count = person.count(25)          # 统计某元素出现次数

# 嵌套元组
nested_tuple = ((1, 2), (3, 4), (5, 6))
first_pair = nested_tuple[0]      # 输出: (1, 2)

# 初始化集合
numbers = {1, 2, 3}

# 添加元素
numbers.add(4)

# 删除元素
numbers.remove(2)            # 移除指定元素
numbers.discard(5)           # 移除指定元素（若不存在不报错）

# 集合运算
odds = {1, 3, 5, 7}
evens = {2, 4, 6, 8}
union_set = odds | evens     # 并集
intersection_set = odds & numbers  # 交集

# 判断是否包含元素
is_present = 3 in numbers

# 输出集合
print(numbers)        # 示例输出: {1, 3, 4}

# 初始化字典
student = {"name": "Alice", "age": 20}

# 添加或更新键值对
student["grade"] = "A"             # 添加新键值对
student["age"] = 21                # 更新已有键值对

# 删除键值对
del student["grade"]

# 查找值
age = student.get("age", "Not found")

# 遍历字典
for key, value in student.items():
    print(f"{key}: {value}")

# 输出字典
print(student)      # 示例输出: {'name': 'Alice', 'age': 21}

函数与模块

def greet(name):
    return f"Hello, {name}!"

print(greet("Alice"))

import math
print(math.sqrt(16))  # 输出: 4.0

def add(a, b=5):
    return a + b

print(add(3))  # 使用默认值 b=5, 输出 8

面向对象编程

class Car:
    def __init__(self, brand, model):
        self.brand = brand
        self.model = model

    def display_info(self):
        print(f"Car: {self.brand} {self.model}")

car1 = Car("Toyota", "Corolla")
car1.display_info()  # 输出: Car: Toyota Corolla

class Car:
    def __init__(self, brand, model):
        self.brand = brand
        self.model = model

    def display_info(self):
        print(f"Car: {self.brand} {self.model}")

car1 = Car("Toyota", "Corolla")
car1.display_info()  # 输出: Car: Toyota Corolla

常用算法实现

# 冒泡排序
def bubble_sort(arr):
    n = len(arr)
    for i in range(n):
        for j in range(0, n-i-1):
            if arr[j] > arr[j+1]:
                arr[j], arr[j+1] = arr[j+1], arr[j]
    return arr

arr = [64, 34, 25, 12, 22, 11, 90]
print(bubble_sort(arr))

# 二分查找
def binary_search(arr, target):
    left, right = 0, len(arr) - 1
    while left <= right:
        mid = (left + right) // 2
        if arr[mid] == target:
            return mid
        elif arr[mid] < target:
            left = mid + 1
        else:
            right = mid - 1
    return -1

sorted_arr = [1, 2, 3, 4, 5]
print(binary_search(sorted_arr, 3))  # 输出: 2

文件操作

# 写入文件
with open("example.txt", "w") as file:
    file.write("Hello, world!")

# 读取文件
with open("example.txt", "r") as file:
    content = file.read()
    print(content)

异常处理

try:
    result = 10 / 0
except ZeroDivisionError:
    print("除数不能为零")
finally:
    print("程序执行结束")

常用库

作者：萨达大