Question

我正在尝试编写一个程序来计算具有不同精度的pi，并打印出已经过去的数字和时间。我想每次都以当前的准确度打印结果。我使用了print('pi = %*f'%(i, pi))，其中i是我当前的浮点精度。这使程序将数字向上舍入为i十进制数字。我正在附上一张图片，显示我的结果运行相同的算法，但改变了输出：

print (" pi = ", pi, " =with ", i-1, " decimal points accuracy= in: ", (-1)*t, "sec")

为：

print (" pi = %.*f"%(i, pi), " =with ", i-1, " decimal points accuracy= in: ", (-1)*t, "sec")

这是我的完整代码：

import time
accuracy = 4
for i in range(1,accuracy + 1):
    pi = 0
    prevPi = 1
    x = 0
    t = time.time()
    while abs((pi * 4) - prevPi) > 10**((-1)*(i+1)):
    #while x < lim:
        prevPi = pi * 4
        pi += (((-1)**(x))/(1+(2*x)))
        #print(abs((pi * 4) - prevPi))
        x += 1
    pi *= 4
    t -= time.time()
    print (" pi = %.*f"%(i, pi), " =with ", i-1, " decimal points accuracy= in: ", (-1)*t, "sec")

如何使用i十进制数字打印数字而不进行舍入？

Answer 1

您可以通过定义截断数字的函数来解决您的问题。该函数可以有两个参数：

number ，
position ，会删除以下所有值。

def truncate(number, position):
    '''Return number with dropped decimal places past specified position.'''
    return number - number%(10**position)

例如，如果您希望将数字3.14截断为3.1，则应调用以下内容：

truncate(3.14, -1)

此外，我修改了您的代码，以便更简单并匹配PEP 8 coding conventions。因此，现在它增加了变量命名清晰度和更好的代码格式。

#!/usr/bin/env python3
'''Module for different pi accuracies calculation time comparison.'''

from time import time

def truncate(number, position):
    '''Return number with dropped decimal places past specified position.'''
    return number - number%(10**position)

def calculate_pi(accuracy):
    '''Return pi with certain floating point accuracy.'''
    previous_pi = 0 
    current_pi = 4 
    iterator = 1 
    while abs(current_pi - previous_pi) > 10 ** (accuracy-1):
        previous_pi = current_pi
        current_pi += 4 * ((-1)**iterator) / (1+(2*iterator))
        iterator += 1
    return truncate(current_pi, accuracy)

def calculation_speed_comparison(max_accuracy):
    '''Print comparison of different accuracy pi calculation time.'''
    for current_accuracy in range(max_accuracy+1):
        calculation_time = time()
        current_pi = calculate_pi(-current_accuracy)
        calculation_time -= time()
        print('pi = {} with {} decimal points accuracy in {} seconds.'.format(
            current_pi, current_accuracy, -calculation_time))

calculation_speed_comparison(4)

此代码的输出与原始代码非常相似：

pi = 3.0 with 0 decimal points accuracy in 3.266334533691406e-05 seconds.
pi = 3.1 with 1 decimal points accuracy in 0.00016045570373535156 seconds.
pi = 3.14 with 2 decimal points accuracy in 0.0014882087707519531 seconds.
pi = 3.141 with 3 decimal points accuracy in 0.01430201530456543 seconds.
pi = 3.1415 with 4 decimal points accuracy in 0.1466822624206543 seconds.

在Python中动态更改浮点精度

1 个答案: