更复杂但更灵活的版本：

units = {

'kg': ('weight', 1.),

'kilo': ('weight', 1.),

'kilogram': ('weight', 1.),

'lb': ('weight', 2.204),

'pound': ('weight', 2.204),

'tonne': ('weight', 0.001),

'carat': ('weight', 5000.),

'gram': ('weight', 1000.),

'dram': ('weight', 564.4),

'ounce': ('weight', 35.27),

'grain': ('weight', 15430.),

'm': ('distance', 1.),

'meter': ('distance', 1.),

'kilometer': ('distance', 0.001),

'km': ('distance', 0.001),

'centimeter': ('distance', 100.),

'cm': ('distance', 100.),

'meter': ('distance', 1.),

'mile': ('distance', 0.0006214),

'chain': ('distance', 0.04971),

'furlong': ('distance', 0.004971),

'league': ('distance', 0.0002071),

'foot': ('distance', 3.281),

'feet': ('distance', 3.281), # irregular plural - must be explicitly specified!

'inch': ('distance', 39.37)

}

def getUnit(unit_name):

if unit_name in units:

return units[unit_name]

# recognize regular plural forms

elif unit_name.endswith('es') and unit_name[:-2] in units:

return units[unit_name[:-2]]

elif unit_name.endswith('s') and unit_name[:-1] in units:

return units[unit_name[:-1]]

# not found?

else:

raise ValueError("Unrecognized unit '{0}'".format(unit_name))

def convert(amt, from_unit, to_unit):

typeA, numA = getUnit(from_unit)

typeB, numB = getUnit(to_unit)

if typeA==typeB:

return amt * numB / numA

else:

raise ValueError("Units are of different types ('{0}' and '{1}')".format(typeA, typeB))

def conversion(s):

"""

Do unit conversion

Accepts a string of the form

"(number) (unitA) [to] (unitB)"

If unitA and unitB are of the same unit-type, returns the converted value.

"""

s = s.strip().lower().split()

if len(s) not in (3, 4):

raise ValueError("Argument string has wrong number of words (should be three or four)")

try:

amt = float(s[0])

except ValueError:

raise ValueError("Argument string must start with a number")

from_unit = s[1]

to_unit = s[-1]

return convert(amt, from_unit, to_unit)

def tryAgain():

s = raw_input('Try again (Y/n)? ').strip().lower()

return 'yes'.startswith(s)

def main():

while True:

s = raw_input("Convert what? (ex: 10 meters to feet) ")

try:

print(": {0}".format(conversion(s)))

except ValueError, v:

print v

if not tryAgain():

break

if __name__=="__main__":

main()

这可以解决诸如10吨到盎司的问题＆＃34;或者＆＃34; 30弗隆到脚＆＃34;。

建议进一步补充：

以距离为单位添加纳米(并测试)。

以重量单位加上短吨和石头(并测试它们)。

以体积为单位添加升，品脱和桶(并测试它们)。

醇>