Python处理浮点数的实用技巧分享

# 四舍五入到整数
print(round(3.14159))  # 输出：3
 
# 四舍五入到小数点后两位
print(round(3.14159, 2))  # 输出：3.14
 
# 四舍五入到小数点后一位
print(round(2.675, 2))  # 输出：2.67

import math
 
print(math.floor(3.7))  # 输出：3
print(math.floor(-3.7))  # 输出：-4

import math
 
print(math.ceil(3.3))  # 输出：4
print(math.ceil(-3.3))  # 输出：-3

from decimal import Decimal, ROUND_HALF_UP, ROUND_HALF_EVEN
 
# 创建 Decimal 对象
num = Decimal('2.675')
 
# 四舍五入到小数点后两位，采用 ROUND_HALF_UP 策略
rounded_num = num.quantize(Decimal('0.01'), rounding=ROUND_HALF_UP)
print(rounded_num)  # 输出：2.68
 
# 四舍五入到小数点后两位，采用 ROUND_HALF_EVEN 策略
rounded_num = num.quantize(Decimal('0.01'), rounding=ROUND_HALF_EVEN)
print(rounded_num)  # 输出：2.67

import numpy as np
 
# 创建数组
arr = np.array([3.14159, 2.675, 3.5])
 
# 四舍五入到整数
rounded_arr = np.round(arr)
print(rounded_arr)  # 输出：[3. 3. 4.]
 
# 四舍五入到小数点后两位
rounded_arr = np.round(arr, 2)
print(rounded_arr)  # 输出：[3.14 2.67 3.5 ]

def custom_round(number, ndigits=0):
    factor = 10 ** ndigits
    return int(number * factor + 0.5 if number >= 0 else number * factor - 0.5) / factor
 
print(custom_round(2.675, 2))  # 输出：2.68
print(custom_round(3.14159, 3))  # 输出：3.142
print(custom_round(-3.14159, 2))  # 输出：-3.14

from decimal import Decimal, ROUND_HALF_UP
 
def calculate_interest(principal, rate, time):
    interest = principal * (rate / 100) * time
    interest = Decimal(interest).quantize(Decimal('0.01'), rounding=ROUND_HALF_UP)
    return interest
 
principal = 1000.0  # 本金
rate = 3.75  # 年利率
time = 1  # 时间（年）
 
interest = calculate_interest(principal, rate, time)
print(f"利息：{interest} 元")  # 输出：利息：37.50 元

import numpy as np
 
def calculate_average(data):
    average = np.mean(data)
    return round(average, 2)
 
data = [2.678, 3.456, 4.789, 5.123, 3.876]
 
average = calculate_average(data)
print(f"平均值：{average}")  # 输出：平均值：4.00

from decimal import Decimal, ROUND_HALF_UP
 
def calculate_speed(distance, time):
    speed = distance / time
    speed = Decimal(speed).quantize(Decimal('0.001'), rounding=ROUND_HALF_UP)
    return speed
 
distance = 123.456  # 距离（米）
time = 12.34  # 时间（秒）
 
speed = calculate_speed(distance, time)
print(f"速度：{speed} 米/秒")  # 输出：速度：10.005 米/秒

from decimal import Decimal, ROUND_HALF_UP
 
def format_amount(amount):
    return Decimal(amount).quantize(Decimal('0.01'), rounding=ROUND_HALF_UP)
 
data = {
    '收入': 123456.789,
    '支出': 98765.432,
    '净利润': 24691.357
}
 
formatted_data = {k: format_amount(v) for k, v in data.items()}
 
print("财务报告")
for item, amount in formatted_data.items():
    print(f"{item}：{amount} 元")

def celsius_to_fahrenheit(celsius):
    fahrenheit = celsius * 9/5 + 32
    return round(fahrenheit, 1)
 
celsius = 36.6
fahrenheit = celsius_to_fahrenheit(celsius)
print(f"{celsius} 摄氏度 = {fahrenheit} 华氏度")  # 输出：36.6 摄氏度 = 97.9 华氏度