Plural String Formatting
Solution 1
Using custom formatter:
import string
class PluralFormatter(string.Formatter):
def get_value(self, key, args, kwargs):
if isinstance(key, int):
return args[key]
if key in kwargs:
return kwargs[key]
if '(' in key and key.endswith(')'):
key, rest = key.split('(', 1)
value = kwargs[key]
suffix = rest.rstrip(')').split(',')
if len(suffix) == 1:
suffix.insert(0, '')
return suffix[0] if value <= 1 else suffix[1]
else:
raise KeyError(key)
data = {'tree': 1, 'bush': 2, 'flower': 3, 'cactus': 0}
formatter = PluralFormatter()
fmt = "{tree} tree{tree(s)}, {bush} bush{bush(es)}, {flower} flower{flower(s)}, {cactus} cact{cactus(i,us)}"
print(formatter.format(fmt, **data))
Output:
1 tree, 2 bushes, 3 flowers, 0 cacti
UPDATE
If you're using Python 3.2+ (str.format_map
was added), you can use the idea of OP (see comment) that use customized dict.
class PluralDict(dict):
def __missing__(self, key):
if '(' in key and key.endswith(')'):
key, rest = key.split('(', 1)
value = super().__getitem__(key)
suffix = rest.rstrip(')').split(',')
if len(suffix) == 1:
suffix.insert(0, '')
return suffix[0] if value <= 1 else suffix[1]
raise KeyError(key)
data = PluralDict({'tree': 1, 'bush': 2, 'flower': 3, 'cactus': 0})
fmt = "{tree} tree{tree(s)}, {bush} bush{bush(es)}, {flower} flower{flower(s)}, {cactus} cact{cactus(i,us)}"
print(fmt.format_map(data))
Output: same as above.
Solution 2
Check out the inflect package. It will pluralize things, as well as do a whole host of other linguistic trickery. There are too many situations to special-case these yourself!
From the docs at the link above:
import inflect
p = inflect.engine()
# UNCONDITIONALLY FORM THE PLURAL
print("The plural of ", word, " is ", p.plural(word))
# CONDITIONALLY FORM THE PLURAL
print("I saw", cat_count, p.plural("cat",cat_count))
For your specific example:
{print(str(count) + " " + p.pluralize(string, count)) for string, count in data.items() }
Solution 3
When you have only two forms, and just need a quick and dirty fix, try 's'[:i^1]
:
for i in range(5):
print(f"{i} bottle{'s'[:i^1]} of beer.")
Output:
0 bottles of beer.
1 bottle of beer.
2 bottles of beer.
3 bottles of beer.
4 bottles of beer.
Explanation:
^
is the bitwise operator XOR (exclusive disjunction).
- When
i
is zero,i ^ 1
evaluates to1
.'s'[:1]
gives's'
. - When
i
is one,i ^ 1
evaluates to0
.'s'[:0]
gives the empty string. - When
i
is more than one,i ^ 1
evaluates to an integer greater than1
(starting with 3, 2, 5, 4, 7, 6, 9, 8..., see https://oeis.org/A004442 for more information). Python doesn't mind and happily returns as many characters of's'
as it can, which is's'
.
My 1 cent ;)
Bonus. For 2-character plural forms (e.g., bush/bushes), use 'es'[:2*i^2]
. More generally, for an n-character plural form, replace 2
by n in the previous expression.
Opposite. In the comments, user @gccallie suggests 's'[i^1:]
to add an 's' to verbs in the third person singular:
for i in range(5):
print(f"{i} bottle{'s'[:i^1]} of beer lie{'s'[i^1:]} on the wall.")
Output:
0 bottles of beer lie on the wall.
1 bottle of beer lies on the wall.
2 bottles of beer lie on the wall.
3 bottles of beer lie on the wall.
4 bottles of beer lie on the wall.
Python interprets the first form as [:stop]
, and the second one as [start:]
.
Edit. A previous, one-character longer version of the original trick used !=
instead of ^
.
Solution 4
Django users have pluralize
, a function used in templates:
You have {{ num_messages }} message{{ num_messages|pluralize }}.
But you can import this into your code and call it directly:
from django.template.defaultfilters import pluralize
f'You have {num_messages} message{pluralize(num_messages)}.'
'You have {} message{}.'.format(num_messages, pluralize(num_messages))
'You have %d message%s' % (num_messages, pluralize(num_messages))
Solution 5
If there's a limited number of words you're gonna pluralize, I found it easier to have them as lists [singular, plural]
, and then make a small function that returns the index given the amount:
def sp(num):
if num == 1:
return 0
else:
return 1
Then it works like this:
lemon = ["lemon", "lemons"]
str = f"Hi I have bought 2 {lemon[sp(2)]}"
And actually you can get a lot of them at once if you split the word:
s = ["","s"]
str = f"Hi I have 1 cow{s[sp(1)]}"
Comments
-
mhlester about 2 years
Given a dictionary of
int
s, I'm trying to format a string with each number, and a pluralization of the item.Sample input
dict
:data = {'tree': 1, 'bush': 2, 'flower': 3, 'cactus': 0}
Sample output
str
:'My garden has 1 tree, 2 bushes, 3 flowers, and 0 cacti'
It needs to work with an arbitrary format string.
The best solution I've come up with is a
PluralItem
class to store two attributes,n
(the original value), ands
(the string's'
if plural, empty string''
if not). Subclassed for different pluralization methodsclass PluralItem(object): def __init__(self, num): self.n = num self._get_s() def _get_s(self): self.s = '' if self.n == 1 else 's' class PluralES(PluralItem): def _get_s(self): self.s = 's' if self.n == 1 else 'es' class PluralI(PluralItem): def _get_s(self): self.s = 'us' if self.n == 1 else 'i'
Then make a new
dict
through comprehension and aclasses
mapping:classes = {'bush': PluralES, 'cactus': PluralI, None: PluralItem} plural_data = {key: classes.get(key, classes[None])(value) for key, value in data.items()}
Lastly, the format string, and implementation:
formatter = 'My garden has {tree.n} tree{tree.s}, {bush.n} bush{bush.s}, {flower.n} flower{flower.s}, and {cactus.n} cact{cactus.s}' print(formatter.format(**plural_data))
Outputs the following:
My garden has 1 tree, 2 bushes, 3 flowers, and 0 cacti
For such an undoubtedly common need, I'm hesitant to throw in the towel with such a convoluted solution.
Is there a way to format a string like this using the built-in
format
method, and minimal additional code? Pseudocode might be something like:"{tree} tree{tree(s)}, {bush} bush{bush(es)}, {flower} flower{flower(s)}, {cactus} cact{cactus(i,us)}".format(data)
where parentheses return the contents if value is plural, or if contents has comma, means plural/singular