# 打印单个对象
print("Hello, World!")  # 输出: Hello, World!

# 打印多个对象，默认用空格分隔
print("Hello", "World", "!")  # 输出: Hello World !

# 使用 sep 参数改变分隔符
print("Hello", "World", "!", sep="-")  # 输出: Hello-World-!

# 使用 end 参数改变结束符
print("Hello", end=" ")
print("World!")  # 输出: Hello World!

# 打印变量
name = "Python"
version = 3.9
print("I am using", name, "version", version)  # 输出: I am using Python version 3.9

# 简单输入
name = input("请输入你的名字: ")
print(f"你好, {name}!")

# 输入并转换为整数
age = int(input("请输入你的年龄: "))
print(f"你明年将是 {age + 1} 岁。")

# 输入多个值
x, y = input("请输入两个数字，用空格分隔: ").split()
x = int(x)
y = int(y)
print(f"它们的和是 {x + y}。")

# 验证输入是否为数字
while True:
  try:
      age = int(input("请输入你的年龄: "))
      if age < 0:
          print("年龄不能为负数，请重新输入。")
          continue
      break
  except ValueError:
      print("请输入有效的数字。")

print(f"你输入的年龄是 {age} 岁。")

# 验证输入是否在有效范围内
while True:
  grade = input("请输入你的成绩 (A/B/C/D/F): ").upper()
  if grade in ['A', 'B', 'C', 'D', 'F']:
      break
  print("无效的成绩，请重新输入。")

print(f"你的成绩是 {grade}。")

# 写入文件
with open("example.txt", "w") as file:
  file.write("Hello, World!
")
  file.write("This is a test file.
")

# 追加写入
with open("example.txt", "a") as file:
  file.write("This line is appended.
")

# 写入多行
lines = ["Line 1
", "Line 2
", "Line 3
"]
with open("example.txt", "w") as file:
  file.writelines(lines)

print("文件写入完成。")

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

# 逐行读取
with open("example.txt", "r") as file:
  for line in file:
      print(line.strip())  # 去除行尾的换行符

# 读取所有行到列表
with open("example.txt", "r") as file:
  lines = file.readlines()
  print(lines)

print("文件读取完成。")

import sys

# 将标准输出重定向到文件
original_stdout = sys.stdout
with open("output.txt", "w") as f:
  sys.stdout = f  # 重定向标准输出
  print("这行文字将被写入文件而不是显示在控制台。")
  sys.stdout = original_stdout  # 恢复标准输出

print("现在输出恢复到控制台。")

# 从文件读取作为标准输入
original_stdin = sys.stdin
with open("input.txt", "r") as f:
  sys.stdin = f  # 重定向标准输入
  name = input()  # 从文件读取一行
  sys.stdin = original_stdin  # 恢复标准输入

print(f"从文件读取的名字是: {name}")

from string import Template

# 创建模板
template = Template("Hello, $name! You are $age years old.")

# 替换变量
name = "Frank"
age = 50
message = template.substitute(name=name, age=age)
print(message)  # 输出: Hello, Frank! You are 50 years old.

# 使用字典替换
data = {"name": "Grace", "age": 55}
message = template.substitute(data)
print(message)  # 输出: Hello, Grace! You are 55 years old.

import json

# 创建字典
person = {
  "name": "Hank",
  "age": 60,
  "city": "New York",
  "hobbies": ["reading", "swimming", "traveling"]
}

# 格式化为 JSON 字符串
json_str = json.dumps(person, indent=4)
print(json_str)

# 写入 JSON 文件
with open("person.json", "w") as file:
  json.dump(person, file, indent=4)

# 从 JSON 文件读取
with open("person.json", "r") as file:
  data = json.load(file)
  print(data["name"])  # 输出: Hank

# 浮点数精度
pi = 3.141592653589793
print(f"Pi: {pi:.2f}")  # 输出: Pi: 3.14
print(f"Pi: {pi:.5f}")  # 输出: Pi: 3.14159

# 千位分隔符
number = 1234567.89
print(f"Number: {number:,}")  # 输出: Number: 1,234,567.89
print(f"Number: {number:,.2f}")  # 输出: Number: 1,234,567.89

# 百分比
percent = 0.75
print(f"Percent: {percent:.1%}")  # 输出: Percent: 75.0%

# 科学计数法
large_number = 1234567890
print(f"Large number: {large_number:e}")  # 输出: Large number: 1.234568e+09
print(f"Large number: {large_number:.2e}")  # 输出: Large number: 1.23e+09