python考试的基础知识

try:
    lst = [1, 2, 3]
    print(lst[5])  # 触发 IndexError
except (IndexError, ZeroDivisionError) as e:
    print(f"发生错误：{e}")

try:
    x = 10 / 0
except Exception as e:
    print(f"捕获所有异常：{e}")

try:
    file = open("test.txt", "r")
    data = file.read()
except FileNotFoundError:
    print("文件未找到！")
finally:
    print("无论是否发生异常，都会执行此处")

try:
    num = int(input("输入一个数字: "))
    result = 100 / num
except ZeroDivisionError:
    print("不能除以零！")
else:
    print(f"计算结果: {result}")

class MyError(Exception):
    """自定义异常类"""
    def __init__(self, message):
        self.message = message
        super().__init__(message)

try:
    raise MyError("这是一个自定义异常")
except MyError as e:
    print(f"捕获到异常: {e}")

try:
    age = int(input("请输入年龄: "))
    if age < 0:
        raise ValueError("年龄不能为负数")
except ValueError as e:
    print(f"异常: {e}")

s = "apple"
print(s[:-1])  # 输出appl
print(s[:-1:]) # 输出appl
print(s[:4])   # 输出appl
print(s[:5])   # 输出apple
print(s[:6])   # 输出apple

s = "banana"
print(s[::-1]) # 输出ananab,逆向
print(s[:-1:-1]) # 输出为空行
print(s[:-1:2]) # 输出为bnn
print(s[:5:2])   # 输出bnn
print(s[:6:-2])   # 输出为空行

"分隔符".join(可迭代对象)

import turtle

turtle.pensize(3)
turtle.pencolor("blue")

for _ in range(4):
    turtle.forward(100)
    turtle.right(90)

turtle.done()

a ="3.14"
print(int(a))
# 输出不是3,而是下面的内容
ValueError: invalid literal for int() with base 10: '3.14'

img1 = ["123","123"]
img2 = ["cnm","123"]

img1 = img2
img1.append([5,6])
print(img2)  # 输出['cnm', '123', [5, 6]]

img1.append(["5","6"])
print(img2)  # 输出['cnm', '123', [5, 6], ['5', '6']]

a = 6
b = 3

print(a / b)   # 2.0  （浮点除法，结果为浮点数）
print(a // b)  # 2    （整除，结果为整数）

print(ord('A'))   # 65
print(chr(65))    # 'A'

print(ord('中'))  # 20013
print(chr(20013)) # '中'

print(0.3 == 0.1 + 0.2) # 打印为False

print(eval("3 + 5 * 2"))  # 输出 13

x = 10
print(eval("x + 5"))  # 输出 15

data = eval("{'name': 'Alice', 'age': 25}")
print(data["name"])  # 输出 Alice

print("姓名: {0}, 年龄: {1}, 姓名: {0}".format(name, age))  # 输出: 姓名: Alice, 年龄: 25, 姓名: Alice

print("姓名: {n}, 年龄: {a}".format(n=name, a=age))  # 输出: 姓名: Alice, 年龄: 25

pi = 3.1415926535
print("圆周率: {:.2f}".format(pi))  # 输出: 圆周率: 3.14

name = "Alice"
age = 25
print("姓名: {}, 年龄: {}".format(name, age))  
# 输出: 姓名: Alice, 年龄: 25

print("姓名: {0}, 年龄: {1}, 再次姓名: {0}".format(name, age))
# 输出: 姓名: Alice, 年龄: 25, 再次姓名: Alice

print("姓名: {n}, 年龄: {a}".format(n=name, a=age))  
# 输出: 姓名: Alice, 年龄: 25

print("{:>10}".format("text"))  # '     text'
print("{:.2f}".format(3.14159))  # '3.14'
print("{:b}".format(10))  # '1010'
print("{:x}".format(255))  # 'ff'
print("{:.2%}".format(0.95))  # '95.00%'
print("{:,}".format(1000000))  # '1,000,000'
print("{:+d}".format(10))  # '+10'

print("{:*>10}".format("hi"))  # 输出: '********hi'
print("{:.2f}".format(3.14159))  # 输出: '3.14'
print("{:b}".format(10))  # 输出: '1010'
print("{:.2%}".format(0.95))  # 输出: '95.00%'

print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)

text = "apple,orange,banana"

# 默认按空格分割
print("Hello World".split())  # ['Hello', 'World']

# 按逗号分割
print(text.split(','))  # ['apple', 'orange', 'banana']

# 限制分割次数
print(text.split(',', 1))  # ['apple', 'orange,banana']

text = "hElLo WoRlD"

print(text.upper())       # HELLO WORLD
print(text.lower())       # hello world
print(text.capitalize())  # Hello world
print(text.title())       # Hello World
print(text.swapcase())    # HeLLo wOrLd

str.replace(old, new, count)

# Unicode 相关
print(ord('你'))  # 20320
print(chr(20320))  # 你

# 进制转换
print(bin(255))  # 0b11111111
print(oct(255))  # 0o377
print(hex(255))  # 0xff
print(int('ff', 16))  # 255

s = "  Hello, World!  "
print(s.strip())  # 'Hello, World!'

s = "---Python---"
print(s.strip("-"))  # 'Python'

s = "  Python  "
print(s.lstrip())  # "Python  "
print(s.rstrip())  # "  Python"

import time

# 获取当前时间戳
print(time.time())  # 1711785600.123456

# 暂停 2 秒
time.sleep(2)

# 获取本地时间
local_time = time.localtime()
print(time.strftime("%Y-%m-%d %H:%M:%S", local_time))  # 2025-03-29 12:34:56

list1 = [1, 2, 3]
list1.extend([4, 5, 6])
print(list1)  # 输出 [1, 2, 3, 4, 5, 6]


list1 = [1, 2, 3]
list1.append([4, 5, 6])
print(list1)  # 输出 [1, 2, 3, [4, 5, 6]]

# 方式 1: 使用 {}
student = {"name": "Alice", "age": 20, "score": 95}

# 方式 2: 使用 dict()
info = dict(name="Bob", age=22, score=88)

# 方式 3: 通过列表或元组
data = dict([("name", "Tom"), ("age", 18)])

print(student)  # {'name': 'Alice', 'age': 20, 'score': 95}

# 直接访问（键不存在会报错）
print(student["name"])  # Alice

# 使用 get() 方法（键不存在返回 None 或默认值）
print(student.get("age"))  # 20
print(student.get("gender", "未知"))  # 未知

student["age"] = 21  # 修改
student["gender"] = "Female"  # 添加

del student["score"]  # 删除 key
print(student.pop("age"))  # 21 (返回被删除的值)
print(student.popitem())  # 随机删除一个键值对
student.clear()  # 清空字典

for key in student:
    print(key, student[key])  # 遍历 key 和 value

for key, value in student.items():
    print(key, ":", value)  # 遍历键值对

list.sort(key=None, reverse=False)

import jieba

text = "我喜欢Python编程"
print(list(jieba.cut(text)))  
# ['我', '喜欢', 'Python', '编程']

print(list(jieba.cut(text, cut_all=True)))  
# ['我', '喜欢', 'Python', '编程']

print(list(jieba.cut_for_search(text)))  
# ['我', '喜欢', 'Python', '编程']

import jieba
import jieba.analyse

text = "人工智能和大数据是未来的趋势"
jieba.add_word("人工智能")  # 添加自定义词
print(jieba.lcut(text))  # ['人工智能', '和', '大数据', '是', '未来', '的', '趋势']

keywords = jieba.analyse.extract_tags(text, topK=2)
print(keywords)  # ['人工智能', '大数据']

file = open("data.txt", "r", encoding="utf-8")  # 以只读模式打开文件

with open("data.txt", "r", encoding="utf-8") as file:
    content = file.read()  # 读取整个文件内容

with open("data.txt", "r", encoding="utf-8") as file:
    for line in file:
        print(line.strip())  # 逐行读取并去除换行符

with open("output.txt", "w", encoding="utf-8") as file:
    file.write("Hello, World!\n")

with open("output.txt", "a", encoding="utf-8") as file:
    file.write("追加内容\n")

file.close()

with open("image.jpg", "rb") as f:
    data = f.read()  # 读取二进制数据