Python中的简单单位转换器

Question

我是编程新手，我正在尝试在 python 中制作一个简单的单位转换器。我想将公制和公制内的单位转换为英制，反之亦然。我已经开始使用此代码，但发现此方法缓慢且效率低下，如何更有效地进行编码？

import math
import time
"""Unit Converter"""
#Welcome and variable setting
print ("Welcome to Sam's Unit Converter")
cat = raw_input ("Which category would you like to convert? we support length(l) and Weight(w):  ")
if cat == ("l"):
unit1 = raw_input ("Which unit would you like to convert from: ")
unit2 = raw_input ("Which unit would you like to convert to: ")
num1 = raw_input ("Enter your value: " )

    ##Calculations  

if unit1 == "cm" and unit2 == "m":
    ans = float(num1)/100       
elif unit1 == "mm" and unit2 == "cm":
    ans = float(num1)/10
elif unit1 == "m" and unit2 == "cm":
    ans = float(num1)*100
elif unit1 == "cm" and unit2 == "mm":
    ans = float(num1)*10
elif unit1 == "mm" and unit2 == "m":
    ans = float(num1)/1000
elif unit1 == "m" and unit2 == "mm":
    ans = float(num1)*1000  
elif unit1 == "km" and unit2 == "m":
    ans = float(num1)*1000
elif unit1 == "m" and unit2 == "km":
    ans = float(num1)/1000
elif unit1 == "mm" and unit2 == "km":
    ans = float(num1)/1000000

谢谢你的帮助。

Answer 1

您可以使用带有转换因子的字典和调用它们的函数。

def convert_SI(val, unit_in, unit_out):
    SI = {'mm':0.001, 'cm':0.01, 'm':1.0, 'km':1000.}
    return val*SI[unit_in]/SI[unit_out]

例子：

In [18]: convert_SI(1, 'm', 'km')
Out[18]: 0.001

In [19]: convert_SI(1, 'km', 'm')
Out[19]: 1000.0

In [20]: convert_SI(1, 'cm', 'm')
Out[20]: 0.01