n = 3.6
result = round(n, 0)  # 保留0位小數(shù)
print(result)         # 輸出: 4.0
print(type(result))   # 輸出: <class 'float'> ? 不是整數(shù)！

print(round(2.5))   # 輸出: 2  ? 不是3
print(round(3.5))   # 輸出: 4
print(round(4.5))   # 輸出: 4  ? 不是5
print(round(5.5))   # 輸出: 6

import math
# 方法1：int() - 直接截?cái)嘈?shù)部分
print(int(3.9))    # 輸出: 3
print(int(-3.9))   # 輸出: -3（注意：向0取整）
# 方法2：math.floor() - 真正的向下取整
print(math.floor(3.9))   # 輸出: 3
print(math.floor(-3.9))  # 輸出: -4（比-3.9小的最大整數(shù)）

import math
print(math.ceil(3.1))    # 輸出: 4
print(math.ceil(-3.1))   # 輸出: -3（比-3.1大的最小整數(shù)）

# 自定義四舍五入函數(shù)（正負(fù)數(shù)都適用）
def my_round(x):
    return int(x + (0.5 if x >= 0 else -0.5))
print(my_round(2.5))   # 輸出: 3
print(my_round(3.4))   # 輸出: 3
print(my_round(-2.5))  # 輸出: -3
print(my_round(-3.4))  # 輸出: -3

import math
# 方法1：int()
print(int(3.9))    # 輸出: 3
print(int(-3.9))   # 輸出: -3
# 方法2：math.trunc()
print(math.trunc(3.9))   # 輸出: 3
print(math.trunc(-3.9))  # 輸出: -3

# 計(jì)算總頁(yè)數(shù)：使用向上取整
total_items = 47
items_per_page = 10
total_pages = math.ceil(total_items / items_per_page)  # 輸出: 5

# 數(shù)組索引必須為整數(shù)，使用向下取整
arr = [1, 2, 3, 4, 5]
index = 2.7
value = arr[math.floor(index)]  # 獲取arr[2] = 3

def round_money(amount):
    """金額四舍五入到分"""
    return int(amount * 100 + (0.5 if amount >= 0 else -0.5)) / 100
print(round_money(12.3456))  # 輸出: 12.35

import timeit
# 測(cè)試各種方法的性能
setup = "import math; x = 3.14159"
methods = {
    "int(x)": "int(x)",
    "math.floor(x)": "math.floor(x)",
    "math.ceil(x)": "math.ceil(x)",
    "round(x)": "round(x)",
    "math.trunc(x)": "math.trunc(x)"
}
for name, code in methods.items():
    time = timeit.timeit(code, setup=setup, number=1000000)
    print(f"{name:15} {time:.6f}秒")