I'm looking to try and keep pluralisation of existing strings as simple as possible, and was wondering if it was possible to get str.format()
to interpret a default value when looking for kwargs. Here's an example:
string = "{number_of_sheep} sheep {has} run away"
dict_compiled_somewhere_else = {'number_of_sheep' : 4, 'has' : 'have'}
string.format(**dict_compiled_somewhere_else)
# gives "4 sheep have run away"
other_dict = {'number_of_sheep' : 1}
string.format(**other_dict)
# gives a key error: u'has'
# What I'd like is for format to somehow default to the key, or perhaps have some way of defining the 'default' value for the 'has' key
# I'd have liked: "1 sheep has run away"
Cheers
As PEP 3101 , string.format(**other_dict)
is not available.
If the index or keyword refers to an item that does not exist, then an IndexError/KeyError should be raised.
A hint for solving the problem is in Customizing Formatters
, PEP 3101
. That uses string.Formatter
.
I improve the example in PEP 3101
:
from string import Formatter
class UnseenFormatter(Formatter):
def get_value(self, key, args, kwds):
if isinstance(key, str):
try:
return kwds[key]
except KeyError:
return key
else:
return Formatter.get_value(key, args, kwds)
string = "{number_of_sheep} sheep {has} run away"
other_dict = {'number_of_sheep' : 1}
fmt = UnseenFormatter()
print fmt.format(string, **other_dict)
The output is
1 sheep has run away
Based on mskimm and Daniel answer, here's a solution that predefines the singular/plural words (whilst correcting a couple of typos in mskimm's).
The only downside is the hard coding of the keyword arg number
(so I can no longer use number_of_sheep
)
from string import Formatter
class Plural(Formatter):
PLURALS = {'has' : 'have'}
def __init__(self):
super(Plural, self).__init__()
def get_value(self, key, args, kwds):
if isinstance(key, str):
try:
return kwds[key]
except KeyError:
if kwds.get('number', 1) == 1:
return key
return self.PLURALS[key]
return super(Plural, self).get_value(key, args, kwds)
string = "{number} sheep {has} run away"
fmt = Plural()
print fmt.format(string, **{'number' : 1})
print fmt.format(string, **{'number' : 2})
Can't see the advantage. You have to check the plurality anyway, cause normally you don't have a fixed number of sheep
class PluralVerb(object):
EXCEPTIONS = {'have': 'has'}
def __init__(self, plural):
self.plural = plural
def __format__(self, verb):
if self.plural:
return verb
if verb in self.EXCEPTIONS:
return self.EXCEPTIONS[verb]
return verb+'s'
number_of_sheep = 4
print "{number_of_sheep} sheep {pl:run} away".format(number_of_sheep=number_of_sheep, pl=PluralVerb(number_of_sheep!=1))
print "{number_of_sheep} sheep {pl:have} run away".format(number_of_sheep=number_of_sheep, pl=PluralVerb(number_of_sheep!=1))
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