如何在Python中將數字四捨五入為有效數字？

Rounding Numbers to Significant Figures in Python

Python provides convenient ways to round floating-point numbers to a specified number of significant figures. This can be useful when displaying values in user interfaces or performing calculations where precision is important.

Method Using Negative Exponents

To round an integer to a specific number of significant digits, you can use negative exponents in the round function. For example, to round to one significant figure, use round(number, -3).

Function for Generalization

For more flexibility, you can create a function to round to any number of significant figures. Here's an example:

from math import log10, floor

def round_to_n(number, n):
    return round(number, -int(floor(log10(abs(number))) - n))

This function takes two arguments: number to be rounded and n representing the number of significant digits.

Example Usage

The round_to_n function can be used as follows:

round_to_n(0.0232, 1)  # 0.02
round_to_n(1234243, 3)  # 1,230,000
round_to_n(13, 1)       # 10
round_to_n(4, 1)        # 4
round_to_n(19, 1)       # 20

Note that for numbers greater than 1, you may need to convert them to integers before applying the rounding function.

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