更改浮点型舍入模式

round(number, ndigits)

# 基本舍入
print(round(3.14159, 2))  # 输出: 3.14
print(round(2.675, 2))     # 输出: 2.67（注意：浮点数精度问题）

from decimal import Decimal, ROUND_HALF_UP, ROUND_HALF_DOWN, ROUND_CEILING, ROUND_FLOOR

# 创建 Decimal 对象
num = Decimal('2.675')

# 使用不同的舍入模式
rounded_half_up = num.quantize(Decimal('0.01'), rounding=ROUND_HALF_UP)
rounded_half_down = num.quantize(Decimal('0.01'), rounding=ROUND_HALF_DOWN)
rounded_ceiling = num.quantize(Decimal('0.01'), rounding=ROUND_CEILING)
rounded_floor = num.quantize(Decimal('0.01'), rounding=ROUND_FLOOR)

print("ROUND_HALF_UP:", rounded_half_up)   # 输出: 2.68
print("ROUND_HALF_DOWN:", rounded_half_down) # 输出: 2.67
print("ROUND_CEILING:", rounded_ceiling)     # 输出: 2.68
print("ROUND_FLOOR:", rounded_floor)          # 输出: 2.67

def round_to_even(n):
    return round(n) if n % 1 != 0.5 else round(n / 2) * 2

print(round_to_even(2.5))  # 输出: 2.0
print(round_to_even(3.5))  # 输出: 4.0