one, the missing Python function
Not all nor any: just the one.
one is a simple function to check if there is a unique value that evaluates to True in an iterable, and return it. Optionally, it receives a callable as the test function.
Examples:
>>> from one import one
>>> one((True, False, False))
True
>>> one((True, False, True))
False
>>> one((0, 0, 'a'))
'a'
>>> one((0, False, None))
False
>>> one((True, True))
False
>>> one(('', 1))
1
>>> one((10, 20, 30, 42), lambda i: i > 40)
42Install
pip install one
Usage
from one import one
Patterns and use cases
one could replace the following patterns:
true_values = [i for i in iterable if cmp(i)]
if len(true_values) == 1:
return true_values[0]
return False
# using one
return one(iterable, cmp)Another pattern, is in a complex condition
if ((a and not b and not c) or
(b and not a and not c) or
(c and not a and not b)):
do_something()
# using one
if one((a, b, c)):
do_something()A very frequent case is when you have values that must exclude each others.
class ShopStore(models.Model):
address = models.CharField(max_length=200, null=True, blank=True)
is_online = models.BooleanField(default=False)
def clean(self):
if not one((self.address, self.is_online)):
raise models.ValidationError(u'A shop must be online or physical, but not both')Send me your examples!
1 maintainer
Metadata
1 maintainer
Release files for one 0.2.1
For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.
Source distribution (sdist)
| File | Size | Uploaded | |
|---|---|---|---|
| one-0.2.1.tar.gz | 5.0 kB | Details |
Built distribution (wheel)
| File | Interpreter | ABI | Platform | Reset |
|---|---|---|---|---|
| one-0.2.1-py2.py3-none-any.whl | Python 2, Python 3 | none | any | Details |
Total release size: 9.2 kB
Release files / one-0.2.1.tar.gz
| Download URL | one-0.2.1.tar.gz |
|---|---|
| Size | 5.0 kB |
| Tags | Source |
|
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No |
Release files / one-0.2.1-py2.py3-none-any.whl
| Download URL | one-0.2.1-py2.py3-none-any.whl |
|---|---|
| Size | 4.2 kB |
| Tags | Python 2 Python 3 |
|
SHA-256 checksum How to use checksums |
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No |
