chatch-up post for Sunday yesterday: python function parameters

Author: Starslayerx

content/posts/fastapi-cookie-header-parameters.md

@@ -144,7 +144,7 @@ X-Token: bar
 ```
 
 返回类似这样
-```Python
+```JSON
 {
     "X-Token values": [
         "bar",
@@ -202,7 +202,7 @@ tool: plumbus
 }
 ```
 
-#### Disable convert undersocres
+#### Disable convert undersocres 禁止转换下划线
 同样可以禁用自动下换线转换
 
 与普通的 Header 参数一样, 如果参数名中包含下划线 undersocre (\_), FastAPI 会自动将其转换为连字符 hypens (-)

content/posts/python-function-parameters.md

@@ -0,0 +1,126 @@
++++
+date = '2025-08-10T10:00:00+08:00'
+draft = false
+title = 'Python Function Parameters'
++++
+今天是周日, 简单写点吧, 简单总结一下 Python 中函数参数
+
+## Python Function Parameters
+Python 函数参数机制非常灵活丰富, 理解各种参数类型及其用法对于写出优雅、易维护的代码非常重要. 本文将介绍 Python 中函数参数的种类与用法, 并详细讲解 Python 3.8 引入的参数分隔符 / 和 *, 帮助你更好地设计函数接口.
+
+#### 1. Postional Arguments 位置参数
+函数定义中最常见的参数, 调用时按顺序传入值
+```Python
+def greet(name, age):
+    print(f"Hello, {name}. You are {age} years old.")
+
+greet("Alice", 30)  # Hello, Alice. You are 30 years old.
+```
+
+#### 2. Keyword Arguments 关键字参数
+调用时以 `key=value` 形式传入, 顺序可变
+```Python
+greet(age=30, name="Alice")
+```
+
+#### 3. Default Arguments 默认参数
+定义函数时给参数赋默认值, 调用时可省略
+```Python
+def greet(name, age=20):
+    print(f"Hello, {name}. You are {age} years old.")
+
+greet("Bob")        # 使用默认年龄20
+greet("Bob", 25)    # 指定年龄
+```
+
+- 注意: 使用默认参数尽量不要使用可变类型(mutable), 例如列表, 因为默认参数是存储在函数中的, 而非函数实例中, 多次调用会改变默认值的内容.
+
+```Python
+def greet(names: list[str] = ["Alice", "Bob"]):
+    ...
+```
+
+若希望使用默认值, 建议使用下面这种方法
+```Python
+def greet(names: list[str] | None = None):
+    if not names:
+        names = ["Alice", "Bob"]
+    ...
+```
+
+同样的, 默认值参数如果为一个表达式, 则是在定义时求值, 而非运行改函数时才求值
+
+
+
+
+#### 4. `*args` 可变位置参数
+用于接收任意数量的位置参数, 形成元组
+```Python
+def sum_all(*args):
+    return sum(args)
+
+sum_all(1, 2, 3)  # 6
+sum_all()         # 0
+```
+
+#### 5. `**kwargs` 可变关键字参数
+用于接收任意数量的关键字参数, 形成字典
+```Python
+def print_info(**kwargs):
+    for k, v in kwargs.items():
+        print(f"{k} = {v}")
+
+print_info(name="Alice", age=30)
+```
+
+### / 和 * 的用法
+Python 3.8 引入了两种新的函数参数分隔符: 斜杠 `/`(forward slash) 和 星号 `*`(asterisk) 符号, 用于更精细地控制参数的调用方式
+
+#### Postional-only parameters (`/`)
+斜杠前的参数必须通过位置传递, 不能用关键字传递
+```Python
+def func(a, b, /, c, d):
+    print(a, b, c, d)
+```
+
+调用时
+```Python
+func(1, 2, c=3, d=4)   # 正确
+func(1, 2, 3, 4)       # 也正确
+func(a=1, b=2, c=3, d=4)  # 错误，a 和 b 不能用关键字传递
+```
+
+用途:
+- 保护函数接口的参数顺序, 避免调用者用关键字修改参数值
+- 兼容一些C语言扩展模块的调用约定
+- 明确哪些参数是"位置专用"的
+
+
+#### Keyword-only parameters (`*`)
+星号后的参数必须用关键字传递, 不能用位置传递
+```Python
+def func(a, b, *, c, d):
+    print(a, b, c, d)
+```
+
+调用时
+```Python
+func(1, 2, c=3, d=4)   # 正确
+func(1, 2, 3, 4)       # 错误，c 和 d 只能用关键字传递
+```
+
+用途:
+- 强制调用者明确指定关键字参数, 提高代码可读性
+- 避免参数顺序引起的混淆
+
+#### Use both `/` and `*` 
+`/` 和 `*` 也可以同时使用
+```Python
+def func(a, b, /, c, d, *, e, f):
+    print(a, b, c, d, e, f)
+```
+
+调用时
+- a 和 b 只能用位置参数传递
+- c 和 d 都可以
+- e 和 f 只能用关键字参数传递

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 posts</p></div></div><div class="ml-12 space-y-3"><article class="group bg-card border-border hover:bg-accent/50 rounded-lg border p-4 transition-all duration-300"><div class="flex items-center justify-between gap-4"><div class="min-w-0 flex-1"><h4 class="text-foreground group-hover:text-primary mb-3 font-medium transition-colors duration-200"><a href=/posts/fastapi-cookie-and-header-parameters/ class=block>Fastapi Cookie and Header Parameters</a></h4><div class="text-muted-foreground flex items-center gap-4 text-xs"><div class="flex items-center gap-1"><svg class="h-3 w-3" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M8 7V3m8 4V3m-9 8h10M5 21h14a2 2 0 002-2V7a2 2 0 00-2-2H5A2 2 0 003 7v12a2 2 0 002 2z"/></svg>
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 <span>3
+min</span></div></div></div></div></article><article class="group bg-card border-border hover:bg-accent/50 rounded-lg border p-4 transition-all duration-300"><div class="flex items-center justify-between gap-4"><div class="min-w-0 flex-1"><h4 class="text-foreground group-hover:text-primary mb-3 font-medium transition-colors duration-200"><a href=/posts/python-function-parameters/ class=block>Python Function Parameters</a></h4><div class="text-muted-foreground flex items-center gap-4 text-xs"><div class="flex items-center gap-1"><svg class="h-3 w-3" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M8 7V3m8 4V3m-9 8h10M5 21h14a2 2 0 002-2V7a2 2 0 00-2-2H5A2 2 0 003 7v12a2 2 0 002 2z"/></svg>
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+<span>2
 min</span></div></div></div></div></article><article class="group bg-card border-border hover:bg-accent/50 rounded-lg border p-4 transition-all duration-300"><div class="flex items-center justify-between gap-4"><div class="min-w-0 flex-1"><h4 class="text-foreground group-hover:text-primary mb-3 font-medium transition-colors duration-200"><a href=/posts/fastapi-body-advanced-uses/ class=block>FastAPI Body Advanced Uses</a></h4><div class="text-muted-foreground flex items-center gap-4 text-xs"><div class="flex items-center gap-1"><svg class="h-3 w-3" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M8 7V3m8 4V3m-9 8h10M5 21h14a2 2 0 002-2V7a2 2 0 00-2-2H5A2 2 0 003 7v12a2 2 0 002 2z"/></svg>
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