PYTHON函数工具partial用法小结

from functools import partial

new_func = partial(func, *args, **kwargs)


- func：要部分应用的原始函数
-*args：要固定的位置参数
- **kwargs：要固定的关键字参数
- 返回一个新的可调用对象 new_func

from functools import partial

#原函数
def func(a, b, c=3):
    return a + b + c

#固定参数生成新函数
new_func = partial(func, 1, c=10)  # 固定 a=1, c=10

#调用时只需传递剩余参数
print(new_func(2))  # 输出: 1 + 2 + 10 = 13

from functools import partial

def power(base, exponent):
    return base ** exponent

#固定 exponent=2，生成平方函数See:这有点像函数工厂
square = partial(power, exponent=2)
print(square(3))  # 3^2=9

#固定 pxponent=3，生成立方函数
cube = partial(power, exponent=3)
print(cube(2))    # 2^3=8

def greet(greeting, name="Guest"):
    return f"{greeting}, {name}!"

#固定 greeting="Hello"
say_hello = partial(greet, greeting="Hello")
print(say_hello("Alice"))  # "Hello, Alice!"

def connect(host, port=8080, timeout=10):
    print(f"Connecting to {host}:{port} (timeout={timeout}s)")

#固定 host 和 timeout，生成新函数
fast_connect = partial(connect, "example.com", timeout=5)
fast_connect(9090)  # 输出: Connecting to example.com:9090 (timeout=5s)

import tkinter as tk
from functools import partial

def create_button(root, text, command):
    btn = tk.Button(root, text=text, command=command)
    btn.pack()

root = tk.Tk()

#为不同按钮绑定不同参数
create_button(root, "Btn1", partial(print, "Button 1 clicked"))
create_button(root, "Btn2", partial(print, "Button 2 clicked"))

from functools import partial
data = [1, 2, 3, 4, 5]

#固定幂次生成函数
square = partial(map, lambda x: x**2)
cube = partial(map, lambda x: x**3)

print(list(square(data)))  # [1, 4, 9, 16, 25]
print(list(cube(data)))    # [1, 8, 27, 64, 125]

from functools import partial, wraps

def log(level, message):
    print(f"[{level}] {message}")

info = partial(log, "INFO")

#定义装饰器工厂
def decorator(level):  # 关键：定义装饰器工厂
    def actual_decorator(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            print(f"Decorated with {level.args[0]}")
            return func(*args, **kwargs)
        return wrapper
    return actual_decorator

#正确应用装饰器
@decorator(level=info)
def my_function():
    pass

my_function()  # 输出: Decorated with INFO

from functools import partial

def example(a, b):
    pass

p = partial(example, 1)
print(p.func)    # <function example at ...>
print(p.args)    # (1,)
print(p.keywords) # {}

from functools import partial

def my_func():
    pass

p = partial(my_func)
print(p.__name__)  # 输出: my_func

class HashablePartial(partial):
    def __hash__(self):
        return hash((self.func, self.args, frozenset(self.keywords.items())))

hp = HashablePartial(print, "test")
cache = {hp: "cached value"}

from functools import partial
def func(a, b, c):
    return (a+b)*c

#正确: 固定 a=1, b=2
p = partial(func, 1, 2)
print(p(3)) # 9
#错误: 无法直接固定 c=3
p = partial(func,3) #3 传递给了a
print(p(1,2)) #8 即:(3+1)*2