问题
I just learnt from Format numbers as currency in Python that the Python module babel provides babel.numbers.format_currency to format numbers as currency. For instance,
from babel.numbers import format_currency
s = format_currency(123456.789, 'USD', locale='en_US') # u'$123,456.79'
s = format_currency(123456.789, 'EUR', locale='fr_FR') # u'123\xa0456,79\xa0\u20ac'
How about the reverse, from currency to numbers, such as $123,456,789.00 --> 123456789? babel provides babel.numbers.parse_number to parse local numbers, but I didn't found something like parse_currency. So, what is the ideal way to parse local currency into numbers?
I went through Python: removing characters except digits from string.
# Way 1
import string
all=string.maketrans('','')
nodigs=all.translate(all, string.digits)
s = '$123,456.79'
n = s.translate(all, nodigs) # 12345679, lost `.`
# Way 2
import re
n = re.sub("\D", "", s) # 12345679
It doesn't take care the decimal separator ..
Remove all non-numeric characters, except for ., from a string (refer to here),
import re
# Way 1:
s = '$123,456.79'
n = re.sub("[^0-9|.]", "", s) # 123456.79
# Way 2:
non_decimal = re.compile(r'[^\d.]+')
s = '$123,456.79'
n = non_decimal.sub('', s) # 123456.79
It does process the decimal separator ..
But the above solutions don't work when coming to, for instance,
from babel.numbers import format_currency
s = format_currency(123456.789, 'EUR', locale='fr_FR') # u'123\xa0456,79\xa0\u20ac'
new_s = s.encode('utf-8') # 123 456,79 €
As you can see, the format of currency varies. What is the ideal way to parse currency into numbers in a general way?
回答1:
Using babel
The babel documentation notes that the number parsing is not fully implemented yes but they have done a lot of work to get currency info into the library. You can use get_currency_name() and get_currency_symbol() to get currency details, and also all other get_... functions to get the normal number details (decimal point, minus sign, etc.).
Using that information you can exclude from a currency string the currency details (name, sign) and groupings (e.g. , in the US). Then you change the decimal details into the ones used by the C locale (- for minus, and . for the decimal point).
This results in this code (i added an object to keep some of the data, which may come handy in further processing):
import re, os
from babel import numbers as n
from babel.core import default_locale
class AmountInfo(object):
def __init__(self, name, symbol, value):
self.name = name
self.symbol = symbol
self.value = value
def parse_currency(value, cur):
decp = n.get_decimal_symbol()
plus = n.get_plus_sign_symbol()
minus = n.get_minus_sign_symbol()
group = n.get_group_symbol()
name = n.get_currency_name(cur)
symbol = n.get_currency_symbol(cur)
remove = [plus, name, symbol, group]
for token in remove:
# remove the pieces of information that shall be obvious
value = re.sub(re.escape(token), '', value)
# change the minus sign to a LOCALE=C minus
value = re.sub(re.escape(minus), '-', value)
# and change the decimal mark to a LOCALE=C decimal point
value = re.sub(re.escape(decp), '.', value)
# just in case remove extraneous spaces
value = re.sub('\s+', '', value)
return AmountInfo(name, symbol, value)
#cur_loc = os.environ['LC_ALL']
cur_loc = default_locale()
print('locale:', cur_loc)
test = [ (n.format_currency(123456.789, 'USD', locale=cur_loc), 'USD')
, (n.format_currency(-123456.78, 'PLN', locale=cur_loc), 'PLN')
, (n.format_currency(123456.789, 'PLN', locale=cur_loc), 'PLN')
, (n.format_currency(123456.789, 'IDR', locale=cur_loc), 'IDR')
, (n.format_currency(123456.789, 'JPY', locale=cur_loc), 'JPY')
, (n.format_currency(-123456.78, 'JPY', locale=cur_loc), 'JPY')
, (n.format_currency(123456.789, 'CNY', locale=cur_loc), 'CNY')
, (n.format_currency(-123456.78, 'CNY', locale=cur_loc), 'CNY')
]
for v,c in test:
print('As currency :', c, ':', v.encode('utf-8'))
info = parse_currency(v, c)
print('As value :', c, ':', info.value)
print('Extra info :', info.name.encode('utf-8')
, info.symbol.encode('utf-8'))
The output looks promising (in US locale):
$ export LC_ALL=en_US
$ ./cur.py
locale: en_US
As currency : USD : b'$123,456.79'
As value : USD : 123456.79
Extra info : b'US Dollar' b'$'
As currency : PLN : b'-z\xc5\x82123,456.78'
As value : PLN : -123456.78
Extra info : b'Polish Zloty' b'z\xc5\x82'
As currency : PLN : b'z\xc5\x82123,456.79'
As value : PLN : 123456.79
Extra info : b'Polish Zloty' b'z\xc5\x82'
As currency : IDR : b'Rp123,457'
As value : IDR : 123457
Extra info : b'Indonesian Rupiah' b'Rp'
As currency : JPY : b'\xc2\xa5123,457'
As value : JPY : 123457
Extra info : b'Japanese Yen' b'\xc2\xa5'
As currency : JPY : b'-\xc2\xa5123,457'
As value : JPY : -123457
Extra info : b'Japanese Yen' b'\xc2\xa5'
As currency : CNY : b'CN\xc2\xa5123,456.79'
As value : CNY : 123456.79
Extra info : b'Chinese Yuan' b'CN\xc2\xa5'
As currency : CNY : b'-CN\xc2\xa5123,456.78'
As value : CNY : -123456.78
Extra info : b'Chinese Yuan' b'CN\xc2\xa5'
And it still works in different locales (Brazil is notable for using the comma as a decimal mark):
$ export LC_ALL=pt_BR
$ ./cur.py
locale: pt_BR
As currency : USD : b'US$123.456,79'
As value : USD : 123456.79
Extra info : b'D\xc3\xb3lar americano' b'US$'
As currency : PLN : b'-PLN123.456,78'
As value : PLN : -123456.78
Extra info : b'Zloti polon\xc3\xaas' b'PLN'
As currency : PLN : b'PLN123.456,79'
As value : PLN : 123456.79
Extra info : b'Zloti polon\xc3\xaas' b'PLN'
As currency : IDR : b'IDR123.457'
As value : IDR : 123457
Extra info : b'Rupia indon\xc3\xa9sia' b'IDR'
As currency : JPY : b'JP\xc2\xa5123.457'
As value : JPY : 123457
Extra info : b'Iene japon\xc3\xaas' b'JP\xc2\xa5'
As currency : JPY : b'-JP\xc2\xa5123.457'
As value : JPY : -123457
Extra info : b'Iene japon\xc3\xaas' b'JP\xc2\xa5'
As currency : CNY : b'CN\xc2\xa5123.456,79'
As value : CNY : 123456.79
Extra info : b'Yuan chin\xc3\xaas' b'CN\xc2\xa5'
As currency : CNY : b'-CN\xc2\xa5123.456,78'
As value : CNY : -123456.78
Extra info : b'Yuan chin\xc3\xaas' b'CN\xc2\xa5'
It is worth to point out that babel has some encoding problems. That is because the locale files (in locale-data) do use different encoding themselves. If you're working with currencies you're familiar with that should not be a problem. But if you try unfamiliar currencies you might run into problems (i just learned that Poland uses iso-8859-2, not iso-8859-1).
来源：https://stackoverflow.com/questions/37580151/parse-currency-into-numbers-in-python