path: root/babel/numbers.py

# -*- coding: utf-8 -*-
#
# Copyright (C) 2007 Edgewall Software
# All rights reserved.
#
# This software is licensed as described in the file COPYING, which
# you should have received as part of this distribution. The terms
# are also available at http://babel.edgewall.org/wiki/License.
#
# This software consists of voluntary contributions made by many
# individuals. For the exact contribution history, see the revision
# history and logs, available at http://babel.edgewall.org/log/.

"""Locale dependent formatting and parsing of numeric data.

The default locale for the functions in this module is determined by the
following environment variables, in that order:

 * ``LC_NUMERIC``,
 * ``LC_ALL``, and
 * ``LANG``
"""
# TODO:
#  Padding and rounding increments in pattern:
#  - http://www.unicode.org/reports/tr35/ (Appendix G.6)
import math
import re
try:
    from decimal import Decimal
    have_decimal = True
except ImportError:
    have_decimal = False

from babel.core import default_locale, Locale

__all__ = ['format_number', 'format_decimal', 'format_currency',
           'format_percent', 'format_scientific', 'parse_number',
           'parse_decimal', 'NumberFormatError']
__docformat__ = 'restructuredtext en'

LC_NUMERIC = default_locale('LC_NUMERIC')

def get_currency_name(currency, locale=LC_NUMERIC):
    """Return the name used by the locale for the specified currency.
    
    >>> get_currency_name('USD', 'en_US')
    u'US Dollar'
    
    :param currency: the currency code
    :param locale: the `Locale` object or locale identifier
    :return: the currency symbol
    :rtype: `unicode`
    :since: version 0.9.4
    """
    return Locale.parse(locale).currencies.get(currency, currency)

def get_currency_symbol(currency, locale=LC_NUMERIC):
    """Return the symbol used by the locale for the specified currency.
    
    >>> get_currency_symbol('USD', 'en_US')
    u'$'
    
    :param currency: the currency code
    :param locale: the `Locale` object or locale identifier
    :return: the currency symbol
    :rtype: `unicode`
    """
    return Locale.parse(locale).currency_symbols.get(currency, currency)

def get_decimal_symbol(locale=LC_NUMERIC):
    """Return the symbol used by the locale to separate decimal fractions.
    
    >>> get_decimal_symbol('en_US')
    u'.'
    
    :param locale: the `Locale` object or locale identifier
    :return: the decimal symbol
    :rtype: `unicode`
    """
    return Locale.parse(locale).number_symbols.get('decimal', u'.')

def get_plus_sign_symbol(locale=LC_NUMERIC):
    """Return the plus sign symbol used by the current locale.
    
    >>> get_plus_sign_symbol('en_US')
    u'+'
    
    :param locale: the `Locale` object or locale identifier
    :return: the plus sign symbol
    :rtype: `unicode`
    """
    return Locale.parse(locale).number_symbols.get('plusSign', u'+')

def get_minus_sign_symbol(locale=LC_NUMERIC):
    """Return the plus sign symbol used by the current locale.
    
    >>> get_minus_sign_symbol('en_US')
    u'-'
    
    :param locale: the `Locale` object or locale identifier
    :return: the plus sign symbol
    :rtype: `unicode`
    """
    return Locale.parse(locale).number_symbols.get('minusSign', u'-')

def get_exponential_symbol(locale=LC_NUMERIC):
    """Return the symbol used by the locale to separate mantissa and exponent.
    
    >>> get_exponential_symbol('en_US')
    u'E'
    
    :param locale: the `Locale` object or locale identifier
    :return: the exponential symbol
    :rtype: `unicode`
    """
    return Locale.parse(locale).number_symbols.get('exponential', u'E')

def get_group_symbol(locale=LC_NUMERIC):
    """Return the symbol used by the locale to separate groups of thousands.
    
    >>> get_group_symbol('en_US')
    u','
    
    :param locale: the `Locale` object or locale identifier
    :return: the group symbol
    :rtype: `unicode`
    """
    return Locale.parse(locale).number_symbols.get('group', u',')

def format_number(number, locale=LC_NUMERIC):
    """Return the given number formatted for a specific locale.
    
    >>> format_number(1099, locale='en_US')
    u'1,099'
    
    :param number: the number to format
    :param locale: the `Locale` object or locale identifier
    :return: the formatted number
    :rtype: `unicode`
    """
    # Do we really need this one?
    return format_decimal(number, locale=locale)

def format_decimal(number, format=None, locale=LC_NUMERIC):
    """Return the given decimal number formatted for a specific locale.
    
    >>> format_decimal(1.2345, locale='en_US')
    u'1.234'
    >>> format_decimal(1.2346, locale='en_US')
    u'1.235'
    >>> format_decimal(-1.2346, locale='en_US')
    u'-1.235'
    >>> format_decimal(1.2345, locale='sv_SE')
    u'1,234'
    >>> format_decimal(12345, locale='de')
    u'12.345'

    The appropriate thousands grouping and the decimal separator are used for
    each locale:
    
    >>> format_decimal(12345.5, locale='en_US')
    u'12,345.5'

    :param number: the number to format
    :param format: 
    :param locale: the `Locale` object or locale identifier
    :return: the formatted decimal number
    :rtype: `unicode`
    """
    locale = Locale.parse(locale)
    if not format:
        format = locale.decimal_formats.get(format)
    pattern = parse_pattern(format)
    return pattern.apply(number, locale)

def format_currency(number, currency, format=None, locale=LC_NUMERIC):
    u"""Return formatted currency value.
    
    >>> format_currency(1099.98, 'USD', locale='en_US')
    u'$1,099.98'
    >>> format_currency(1099.98, 'USD', locale='es_CO')
    u'US$\\xa01.099,98'
    >>> format_currency(1099.98, 'EUR', locale='de_DE')
    u'1.099,98\\xa0\\u20ac'
    
    The pattern can also be specified explicitly:
    
    >>> format_currency(1099.98, 'EUR', u'\xa4\xa4 #,##0.00', locale='en_US')
    u'EUR 1,099.98'
    
    :param number: the number to format
    :param currency: the currency code
    :param locale: the `Locale` object or locale identifier
    :return: the formatted currency value
    :rtype: `unicode`
    """
    locale = Locale.parse(locale)
    if not format:
        format = locale.currency_formats.get(format)
    pattern = parse_pattern(format)
    return pattern.apply(number, locale, currency=currency)

def format_percent(number, format=None, locale=LC_NUMERIC):
    """Return formatted percent value for a specific locale.
    
    >>> format_percent(0.34, locale='en_US')
    u'34%'
    >>> format_percent(25.1234, locale='en_US')
    u'2,512%'
    >>> format_percent(25.1234, locale='sv_SE')
    u'2\\xa0512\\xa0%'

    The format pattern can also be specified explicitly:
    
    >>> format_percent(25.1234, u'#,##0\u2030', locale='en_US')
    u'25,123\u2030'

    :param number: the percent number to format
    :param format: 
    :param locale: the `Locale` object or locale identifier
    :return: the formatted percent number
    :rtype: `unicode`
    """
    locale = Locale.parse(locale)
    if not format:
        format = locale.percent_formats.get(format)
    pattern = parse_pattern(format)
    return pattern.apply(number, locale)

def format_scientific(number, format=None, locale=LC_NUMERIC):
    """Return value formatted in scientific notation for a specific locale.
    
    >>> format_scientific(10000, locale='en_US')
    u'1E4'

    The format pattern can also be specified explicitly:
    
    >>> format_scientific(1234567, u'##0E00', locale='en_US')
    u'1.23E06'

    :param number: the number to format
    :param format: 
    :param locale: the `Locale` object or locale identifier
    :return: value formatted in scientific notation.
    :rtype: `unicode`
    """
    locale = Locale.parse(locale)
    if not format:
        format = locale.scientific_formats.get(format)
    pattern = parse_pattern(format)
    return pattern.apply(number, locale)


class NumberFormatError(ValueError):
    """Exception raised when a string cannot be parsed into a number."""


def parse_number(string, locale=LC_NUMERIC):
    """Parse localized number string into a long integer.
    
    >>> parse_number('1,099', locale='en_US')
    1099L
    >>> parse_number('1.099', locale='de_DE')
    1099L
    
    When the given string cannot be parsed, an exception is raised:
    
    >>> parse_number('1.099,98', locale='de')
    Traceback (most recent call last):
        ...
    NumberFormatError: '1.099,98' is not a valid number
    
    :param string: the string to parse
    :param locale: the `Locale` object or locale identifier
    :return: the parsed number
    :rtype: `long`
    :raise `NumberFormatError`: if the string can not be converted to a number
    """
    try:
        return long(string.replace(get_group_symbol(locale), ''))
    except ValueError:
        raise NumberFormatError('%r is not a valid number' % string)

def parse_decimal(string, locale=LC_NUMERIC):
    """Parse localized decimal string into a float.
    
    >>> parse_decimal('1,099.98', locale='en_US')
    1099.98
    >>> parse_decimal('1.099,98', locale='de')
    1099.98
    
    When the given string cannot be parsed, an exception is raised:
    
    >>> parse_decimal('2,109,998', locale='de')
    Traceback (most recent call last):
        ...
    NumberFormatError: '2,109,998' is not a valid decimal number
    
    :param string: the string to parse
    :param locale: the `Locale` object or locale identifier
    :return: the parsed decimal number
    :rtype: `float`
    :raise `NumberFormatError`: if the string can not be converted to a
                                decimal number
    """
    locale = Locale.parse(locale)
    try:
        return float(string.replace(get_group_symbol(locale), '')
                           .replace(get_decimal_symbol(locale), '.'))
    except ValueError:
        raise NumberFormatError('%r is not a valid decimal number' % string)


PREFIX_END = r'[^0-9@#.,]'
NUMBER_TOKEN = r'[0-9@#.\-,E+]'

PREFIX_PATTERN = r"(?P<prefix>(?:'[^']*'|%s)*)" % PREFIX_END
NUMBER_PATTERN = r"(?P<number>%s+)" % NUMBER_TOKEN
SUFFIX_PATTERN = r"(?P<suffix>.*)"

number_re = re.compile(r"%s%s%s" % (PREFIX_PATTERN, NUMBER_PATTERN,
                                    SUFFIX_PATTERN))

def split_number(value):
    """Convert a number into a (intasstring, fractionasstring) tuple"""
    if have_decimal and isinstance(value, Decimal):
        text = str(value)
    else:
        text = ('%.9f' % value).rstrip('0')
    if '.' in text:
        a, b = text.split('.', 1)
        if b == '0':
            b = ''
    else:
        a, b = text, ''
    return a, b

def bankersround(value, ndigits=0):
    """Round a number to a given precision.

    Works like round() except that the round-half-even (banker's rounding)
    algorithm is used instead of round-half-up.

    >>> bankersround(5.5, 0)
    6.0
    >>> bankersround(6.5, 0)
    6.0
    >>> bankersround(-6.5, 0)
    -6.0
    >>> bankersround(1234.0, -2)
    1200.0
    """
    sign = int(value < 0) and -1 or 1
    value = abs(value)
    a, b = split_number(value)
    digits = a + b
    add = 0
    i = len(a) + ndigits
    if i < 0 or i >= len(digits):
        pass
    elif digits[i] > '5':
        add = 1
    elif digits[i] == '5' and digits[i-1] in '13579':
        add = 1
    scale = 10**ndigits
    if have_decimal and isinstance(value, Decimal):
        return Decimal(int(value * scale + add)) / scale * sign
    else:
        return float(int(value * scale + add)) / scale * sign

def parse_pattern(pattern):
    """Parse number format patterns"""
    if isinstance(pattern, NumberPattern):
        return pattern

    # Do we have a negative subpattern?
    if ';' in pattern:
        pattern, neg_pattern = pattern.split(';', 1)
        pos_prefix, number, pos_suffix = number_re.search(pattern).groups()
        neg_prefix, _, neg_suffix = number_re.search(neg_pattern).groups()
    else:
        pos_prefix, number, pos_suffix = number_re.search(pattern).groups()
        neg_prefix = '-' + pos_prefix
        neg_suffix = pos_suffix
    if 'E' in number:
        number, exp = number.split('E', 1)
    else:
        exp = None
    if '@' in number:
        if '.' in number and '0' in number:
            raise ValueError('Significant digit patterns can not contain '
                             '"@" or "0"')
    if '.' in number:
        integer, fraction = number.rsplit('.', 1)
    else:
        integer = number
        fraction = ''
    min_frac = max_frac = 0

    def parse_precision(p):
        """Calculate the min and max allowed digits"""
        min = max = 0
        for c in p:
            if c in '@0':
                min += 1
                max += 1
            elif c == '#':
                max += 1
            elif c == ',':
                continue
            else:
                break
        return min, max

    def parse_grouping(p):
        """Parse primary and secondary digit grouping

        >>> parse_grouping('##')
        0, 0
        >>> parse_grouping('#,###')
        3, 3
        >>> parse_grouping('#,####,###')
        3, 4
        """
        width = len(p)
        g1 = p.rfind(',')
        if g1 == -1:
            return 1000, 1000
        g1 = width - g1 - 1
        g2 = p[:-g1 - 1].rfind(',')
        if g2 == -1:
            return g1, g1
        g2 = width - g1 - g2 - 2
        return g1, g2

    int_prec = parse_precision(integer)
    frac_prec = parse_precision(fraction)
    if exp:
        frac_prec = parse_precision(integer+fraction)
        exp_plus = exp.startswith('+')
        exp = exp.lstrip('+')
        exp_prec = parse_precision(exp)
    else:
        exp_plus = None
        exp_prec = None
    grouping = parse_grouping(integer)
    return NumberPattern(pattern, (pos_prefix, neg_prefix), 
                         (pos_suffix, neg_suffix), grouping,
                         int_prec, frac_prec, 
                         exp_prec, exp_plus)


class NumberPattern(object):

    def __init__(self, pattern, prefix, suffix, grouping,
                 int_prec, frac_prec, exp_prec, exp_plus):
        self.pattern = pattern
        self.prefix = prefix
        self.suffix = suffix
        self.grouping = grouping
        self.int_prec = int_prec
        self.frac_prec = frac_prec
        self.exp_prec = exp_prec
        self.exp_plus = exp_plus
        if '%' in ''.join(self.prefix + self.suffix):
            self.scale = 100
        elif u'‰' in ''.join(self.prefix + self.suffix):
            self.scale = 1000
        else:
            self.scale = 1

    def __repr__(self):
        return '<%s %r>' % (type(self).__name__, self.pattern)

    def apply(self, value, locale, currency=None):
        value *= self.scale
        is_negative = int(value < 0)
        if self.exp_prec: # Scientific notation
            value = abs(value)
            if value:
                exp = int(math.floor(math.log(value, 10)))
            else:
                exp = 0
            # Minimum number of integer digits
            if self.int_prec[0] == self.int_prec[1]:
                exp -= self.int_prec[0] - 1
            # Exponent grouping
            elif self.int_prec[1]:
                exp = int(exp) / self.int_prec[1] * self.int_prec[1]
            if not have_decimal or not isinstance(value, Decimal):
                value = float(value)
            if exp < 0:
                value = value * 10**(-exp)
            else:
                value = value / 10**exp
            exp_sign = ''
            if exp < 0:
                exp_sign = get_minus_sign_symbol(locale)
            elif self.exp_plus:
                exp_sign = get_plus_sign_symbol(locale)
            exp = abs(exp)
            number = u'%s%s%s%s' % \
                 (self._format_sigdig(value, self.frac_prec[0], 
                                     self.frac_prec[1]), 
                  get_exponential_symbol(locale),  exp_sign,
                  self._format_int(str(exp), self.exp_prec[0],
                                   self.exp_prec[1], locale))
        elif '@' in self.pattern: # Is it a siginificant digits pattern?
            text = self._format_sigdig(abs(value),
                                      self.int_prec[0],
                                      self.int_prec[1])
            if '.' in text:
                a, b = text.split('.')
                a = self._format_int(a, 0, 1000, locale)
                if b:
                    b = get_decimal_symbol(locale) + b
                number = a + b
            else:
                number = self._format_int(text, 0, 1000, locale)
        else: # A normal number pattern
            a, b = split_number(bankersround(abs(value), 
                                             self.frac_prec[1]))
            b = b or '0'
            a = self._format_int(a, self.int_prec[0],
                                 self.int_prec[1], locale)
            b = self._format_frac(b, locale)
            number = a + b
        retval = u'%s%s%s' % (self.prefix[is_negative], number,
                                self.suffix[is_negative])
        if u'¤' in retval:
            retval = retval.replace(u'¤¤', currency.upper())
            retval = retval.replace(u'¤', get_currency_symbol(currency, locale))
        return retval

    def _format_sigdig(self, value, min, max):
        """Convert value to a string.

        The resulting string will contain between (min, max) number of
        significant digits.
        """
        a, b = split_number(value)
        ndecimals = len(a)
        if a == '0' and b != '':
            ndecimals = 0
            while b.startswith('0'):
                b = b[1:]
                ndecimals -= 1
        a, b = split_number(bankersround(value, max - ndecimals))
        digits = len((a + b).lstrip('0'))
        if not digits:
            digits = 1
        # Figure out if we need to add any trailing '0':s
        if len(a) >= max and a != '0':
            return a
        if digits < min:
            b += ('0' * (min - digits))
        if b:
            return '%s.%s' % (a, b)
        return a

    def _format_int(self, value, min, max, locale):
        width = len(value)
        if width < min:
            value = '0' * (min - width) + value
        gsize = self.grouping[0]
        ret = ''
        symbol = get_group_symbol(locale)
        while len(value) > gsize:
            ret = symbol + value[-gsize:] + ret
            value = value[:-gsize]
            gsize = self.grouping[1]
        return value + ret

    def _format_frac(self, value, locale):
        min, max = self.frac_prec
        if len(value) < min:
            value += ('0' * (min - len(value)))
        if max == 0 or (min == 0 and int(value) == 0):
            return ''
        width = len(value)
        while len(value) > min and value[-1] == '0':
            value = value[:-1]
        return get_decimal_symbol(locale) + value