### Python 中 `f-string` 的用法 #### 定义与基本语法 `f-string` 是一种格式化字符串字面量的方法，在字符串前加上字母 `f` 或者 `F` 来启用此功能。这允许在字符串内部嵌入表达式，这些表达式的值会被计算并替换到最终输出中。 ```python name = "Alice" age = 30 formatted_string = f"My name is {name}, and I am {age} years old." print(formatted_string) ``` 上述代码会打印出 `"My name is Alice, and I am 30 years old."`[^1] #### 表达式求值 可以在大括号内放置任何合法的 Python 表达式： ```python x = 5 y = 10 result = f"The sum of {x} and {y} is {x + y}." print(result) # 输出："The sum of 5 and 10 is 15." ``` #### 调用方法和属性访问 可以直接调用对象的方法或访问其属性而无需事先赋值给变量： ```python text = "hello world" uppercased = f"{text.upper()}" length_info = f"Length of '{text}' is {len(text)}" print(uppercased) # 输出："HELLO WORLD" print(length_info) # 输出："Length of 'hello world' is 11" ``` #### 数字格式化 支持简单的数字格式化选项来控制数值显示方式： ```python pi_value = 3.141592653589793 formatted_pi = f"Pi rounded to two decimal places: {pi_value:.2f}" percentage = 0.75 percent_format = f"Percentage value: {percentage:%}" scientific_notation = f"Scientific notation: {pi_value:e}" print(formatted_pi) # Pi rounded to two decimal places: 3.14 print(percent_format) # Percentage value: 75% print(scientific_notation) # Scientific notation: 3.141593e+00 ```