Simple yet flexible natural sorting in Python.
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Simple yet flexible natural sorting in Python.
- Source Code: https://github.com/SethMMorton/natsort
- Downloads: https://pypi.org/project/natsort/
- Documentation: https://natsort.readthedocs.io/
- `Examples and Recipes`_
- `How Does Natsort Work?`_
- `API`_
- `Quick Description`_
- `Quick Examples`_
- `FAQ`_
- `Requirements`_
- `Optional Dependencies`_
- `Installation`_
- `How to Run Tests`_
- `How to Build Documentation`_
- `Dropped Deprecated APIs`_
- `History`_
NOTE: Please see the Dropped Deprecated APIs
_ section for changes.
When you try to sort a list of strings that contain numbers, the normal python sort algorithm sorts lexicographically, so you might not get the results that you expect:
.. code-block:: pycon
>>> a = ['2 ft 7 in', '1 ft 5 in', '10 ft 2 in', '2 ft 11 in', '7 ft 6 in']
>>> sorted(a)
['1 ft 5 in', '10 ft 2 in', '2 ft 11 in', '2 ft 7 in', '7 ft 6 in']
Notice that it has the order ('1', '10', '2') - this is because the list is being sorted in lexicographical order, which sorts numbers like you would letters (i.e. 'b', 'ba', 'c').
natsort
_ provides a function natsorted()
_ that helps sort lists
"naturally" ("naturally" is rather ill-defined, but in general it means
sorting based on meaning and not computer code point).
Using natsorted()
_ is simple:
.. code-block:: pycon
>>> from natsort import natsorted
>>> a = ['2 ft 7 in', '1 ft 5 in', '10 ft 2 in', '2 ft 11 in', '7 ft 6 in']
>>> natsorted(a)
['1 ft 5 in', '2 ft 7 in', '2 ft 11 in', '7 ft 6 in', '10 ft 2 in']
natsorted()
_ identifies numbers anywhere in a string and sorts them
naturally. Below are some other things you can do with natsort
_
(also see the Examples and Recipes
_ for a quick start guide, or the
API
_ for complete details).
Note: natsorted()
_ is designed to be a drop-in replacement for the
built-in sorted()
_ function. Like sorted()
, natsorted()
does not sort in-place
. To sort a list and assign the output to the same
variable, you must explicitly assign the output to a variable:
.. code-block:: pycon
>>> a = ['2 ft 7 in', '1 ft 5 in', '10 ft 2 in', '2 ft 11 in', '7 ft 6 in']
>>> natsorted(a)
['1 ft 5 in', '2 ft 7 in', '2 ft 11 in', '7 ft 6 in', '10 ft 2 in']
>>> print(a) # 'a' was not sorted; "natsorted" simply returned a sorted list
['2 ft 7 in', '1 ft 5 in', '10 ft 2 in', '2 ft 11 in', '7 ft 6 in']
>>> a = natsorted(a) # Now 'a' will be sorted because the sorted list was assigned to 'a'
>>> print(a)
['1 ft 5 in', '2 ft 7 in', '2 ft 11 in', '7 ft 6 in', '10 ft 2 in']
Please see Generating a Reusable Sorting Key and Sorting In-Place
_ for
an alternate way to sort in-place naturally.
Sorting Versions
_Sort Paths Like My File Browser (e.g. Windows Explorer on Windows)
_Sorting by Real Numbers (i.e. Signed Floats)
_Locale-Aware Sorting (or "Human Sorting")
_Further Customizing Natsort
_Sorting Mixed Types
_Handling Bytes
_Generating a Reusable Sorting Key and Sorting In-Place
_Other Useful Things
_Sorting Versions ++++++++++++++++
natsort
_ does not actually comprehend version numbers.
It just so happens that the most common versioning schemes are designed to
work with standard natural sorting techniques; these schemes include
MAJOR.MINOR
, MAJOR.MINOR.PATCH
, YEAR.MONTH.DAY
. If your data
conforms to a scheme like this, then it will work out-of-the-box with
natsorted()
_ (as of natsort
_ version >= 4.0.0):
.. code-block:: pycon
>>> a = ['version-1.9', 'version-2.0', 'version-1.11', 'version-1.10']
>>> natsorted(a)
['version-1.9', 'version-1.10', 'version-1.11', 'version-2.0']
If you need to versions that use a more complicated scheme, please see
these version sorting examples
_.
Sort Paths Like My File Browser (e.g. Windows Explorer on Windows) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Prior to natsort
_ version 7.1.0, it was a common request to be able to
sort paths like Windows Explorer. As of natsort
_ 7.1.0, the function
os_sorted()
_ has been added to provide users the ability to sort
in the order that their file browser might sort (e.g Windows Explorer on
Windows, Finder on MacOS, Dolphin/Nautilus/Thunar/etc. on Linux).
.. code-block:: python
import os
from natsort import os_sorted
print(os_sorted(os.listdir()))
# The directory sorted like your file browser might show
Output will be different depending on the operating system you are on.
For users not on Windows (e.g. MacOS/Linux) it is strongly recommended
to also install PyICU
, which will help
natsort
give results that match most file browsers. If this is not installed,
it will fall back on Python's built-in locale
_ module and will give good
results for most input, but will give poor results for special characters.
Sorting by Real Numbers (i.e. Signed Floats) ++++++++++++++++++++++++++++++++++++++++++++
This is useful in scientific data analysis (and was the default behavior
of natsorted()
_ for natsort
_ version < 4.0.0). Use the realsorted()
_
function:
.. code-block:: pycon
>>> from natsort import realsorted, ns
>>> # Note that when interpreting as signed floats, the below numbers are
>>> # +5.10, -3.00, +5.30, +2.00
>>> a = ['position5.10.data', 'position-3.data', 'position5.3.data', 'position2.data']
>>> natsorted(a)
['position2.data', 'position5.3.data', 'position5.10.data', 'position-3.data']
>>> natsorted(a, alg=ns.REAL)
['position-3.data', 'position2.data', 'position5.10.data', 'position5.3.data']
>>> realsorted(a) # shortcut for natsorted with alg=ns.REAL
['position-3.data', 'position2.data', 'position5.10.data', 'position5.3.data']
Locale-Aware Sorting (or "Human Sorting") +++++++++++++++++++++++++++++++++++++++++
This is where the non-numeric characters are also ordered based on their
meaning, not on their ordinal value, and a locale-dependent thousands
separator and decimal separator is accounted for in the number.
This can be achieved with the humansorted()
_ function:
.. code-block:: pycon
>>> a = ['Apple', 'apple15', 'Banana', 'apple14,689', 'banana']
>>> natsorted(a)
['Apple', 'Banana', 'apple14,689', 'apple15', 'banana']
>>> import locale
>>> locale.setlocale(locale.LC_ALL, 'en_US.UTF-8')
'en_US.UTF-8'
>>> natsorted(a, alg=ns.LOCALE)
['apple15', 'apple14,689', 'Apple', 'banana', 'Banana']
>>> from natsort import humansorted
>>> humansorted(a) # shortcut for natsorted with alg=ns.LOCALE
['apple15', 'apple14,689', 'Apple', 'banana', 'Banana']
You may find you need to explicitly set the locale to get this to work
(as shown in the example). Please see locale issues
_ and the
Optional Dependencies
_ section below before using the humansorted()
_ function.
Further Customizing Natsort +++++++++++++++++++++++++++
If you need to combine multiple algorithm modifiers (such as ns.REAL
,
ns.LOCALE
, and ns.IGNORECASE
), you can combine the options using the
bitwise OR operator (|
). For example,
.. code-block:: pycon
>>> a = ['Apple', 'apple15', 'Banana', 'apple14,689', 'banana']
>>> natsorted(a, alg=ns.REAL | ns.LOCALE | ns.IGNORECASE)
['Apple', 'apple15', 'apple14,689', 'Banana', 'banana']
>>> # The ns enum provides long and short forms for each option.
>>> ns.LOCALE == ns.L
True
>>> # You can also customize the convenience functions, too.
>>> natsorted(a, alg=ns.REAL | ns.LOCALE | ns.IGNORECASE) == realsorted(a, alg=ns.L | ns.IC)
True
>>> natsorted(a, alg=ns.REAL | ns.LOCALE | ns.IGNORECASE) == humansorted(a, alg=ns.R | ns.IC)
True
All of the available customizations can be found in the documentation for
the ns enum
_.
You can also add your own custom transformation functions with the key
argument. These can be used with alg
if you wish.
.. code-block:: pycon
>>> a = ['apple2.50', '2.3apple']
>>> natsorted(a, key=lambda x: x.replace('apple', ''), alg=ns.REAL)
['2.3apple', 'apple2.50']
Sorting Mixed Types +++++++++++++++++++
You can mix and match int
, float
, and str
_ types when you sort:
.. code-block:: pycon
>>> a = ['4.5', 6, 2.0, '5', 'a']
>>> natsorted(a)
[2.0, '4.5', '5', 6, 'a']
>>> # sorted(a) would raise an "unorderable types" TypeError
Handling Bytes ++++++++++++++
natsort
_ does not officially support the bytes
_ type, but
convenience functions are provided that help you decode to str
_ first:
.. code-block:: pycon
>>> from natsort import as_utf8
>>> a = [b'a', 14.0, 'b']
>>> # natsorted(a) would raise a TypeError (bytes() < str())
>>> natsorted(a, key=as_utf8) == [14.0, b'a', 'b']
True
>>> a = [b'a56', b'a5', b'a6', b'a40']
>>> # natsorted(a) would return the same results as sorted(a)
>>> natsorted(a, key=as_utf8) == [b'a5', b'a6', b'a40', b'a56']
True
Generating a Reusable Sorting Key and Sorting In-Place ++++++++++++++++++++++++++++++++++++++++++++++++++++++
Under the hood, natsorted()
_ works by generating a custom sorting
key using natsort_keygen()
_ and then passes that to the built-in
sorted()
. You can use the natsort_keygen()
function yourself to
generate a custom sorting key to sort in-place using the list.sort()
_
method.
.. code-block:: pycon
>>> from natsort import natsort_keygen
>>> natsort_key = natsort_keygen()
>>> a = ['2 ft 7 in', '1 ft 5 in', '10 ft 2 in', '2 ft 11 in', '7 ft 6 in']
>>> natsorted(a) == sorted(a, key=natsort_key)
True
>>> a.sort(key=natsort_key)
>>> a
['1 ft 5 in', '2 ft 7 in', '2 ft 11 in', '7 ft 6 in', '10 ft 2 in']
All of the algorithm customizations mentioned in the
Further Customizing Natsort
_ section can also be applied to
natsort_keygen()
_ through the alg keyword option.
Other Useful Things +++++++++++++++++++
controlling the case-sensitivity
_sorting file paths correctly
_allow custom sorting keys
_accounting for units
_How do I debug natsorted()
?
The best way to debug natsorted()
is to generate a key using natsort_keygen()
_
with the same options being passed to natsorted()
. One can take a look at
exactly what is being done with their input using this key - it is highly
recommended to look at this issue describing how to debug
for how to debug,
and also to review the How Does Natsort Work?
_ page for why natsort
_ is
doing that to your data.
If you are trying to sort custom classes and running into trouble, please
take a look at https://github.com/SethMMorton/natsort/issues/60. In short,
custom classes are not likely to be sorted correctly if one relies
on the behavior of ``__lt__`` and the other rich comparison operators in
their custom class - it is better to use a ``key`` function with
`natsort`_, or use the `natsort`_ key as part of your rich comparison
operator definition.
natsort
_ gave me results I didn't expect, and it's a terrible library!
Did you try to debug using the above advice? If so, and you still cannot figure out
the error, then please file an issue
_.
How does natsort
_ work?
If you don't want to read How Does Natsort Work?
_,
here is a quick primer.
`natsort`_ provides a `key function`_ that can be passed to `list.sort()`_
or `sorted()`_ in order to modify the default sorting behavior. This key
is generated on-demand with the key generator `natsort_keygen()`_.
`natsorted()`_ is essentially a wrapper for the following code:
.. code-block:: pycon
>>> from natsort import natsort_keygen
>>> natsort_key = natsort_keygen()
>>> sorted(['1', '10', '2'], key=natsort_key)
['1', '2', '10']
Users can further customize `natsort`_ sorting behavior with the ``key``
and/or ``alg`` options (see details in the `Further Customizing Natsort`_
section).
The key generated by `natsort_keygen()`_ *always* returns a `tuple`_. It
does so in the following way (*some details omitted for clarity*):
1. Assume the input is a string, and attempt to split it into numbers and
non-numbers using regular expressions. Numbers are then converted into
either `int`_ or `float`_.
2. If the above fails because the input is not a string, assume the input
is some other sequence (e.g. `list`_ or `tuple`_), and recursively
apply the key to each element of the sequence.
3. If the above fails because the input is not iterable, assume the input
is an `int`_ or `float`_, and just return the input in a `tuple`_.
Because a `tuple`_ is always returned, a `TypeError`_ should not be common
unless one tries to do something odd like sort an `int`_ against a `list`_.
natsort
_ comes with a shell script called natsort
, or can also be called
from the command line with python -m natsort
. Check out the
shell script wiki documentation
for more details.
natsort
_ requires Python 3.7 or greater.
fastnumbers +++++++++++
The most efficient sorting can occur if you install the
fastnumbers
_ package
(version >=2.0.0); it helps with the string to number conversions.
natsort
_ will still run (efficiently) without the package, but if you need
to squeeze out that extra juice it is recommended you include this as a
dependency. natsort
_ will not require (or check) that
fastnumbers
_ is installed at installation.
PyICU +++++
It is recommended that you install PyICU
_ if you wish to sort in a
locale-dependent manner, see this page on locale issues
_ for an explanation why.
Use pip
!
.. code-block:: console
$ pip install natsort
If you want to install the Optional Dependencies
, you can use the
"extras" notation
at installation time to install those dependencies as
well - use fast
for fastnumbers
_ and icu
for PyICU
_.
.. code-block:: console
# Install both optional dependencies.
$ pip install natsort[fast,icu]
# Install just fastnumbers
$ pip install natsort[fast]
Please note that natsort
_ is NOT set-up to support python setup.py test
.
The recommended way to run tests is with tox
. After installing tox
,
running tests is as simple as executing the following in the natsort
directory:
.. code-block:: console
$ tox
tox
will create virtual a virtual environment for your tests and install
all the needed testing requirements for you. You can specify a particular
python version with the -e
flag, e.g. tox -e py36
. Static analysis
is done with tox -e flake8
. You can see all available testing environments
with tox --listenvs
.
If you want to build the documentation for natsort
_, it is recommended to
use tox
:
.. code-block:: console
$ tox -e docs
This will place the documentation in build/sphinx/html
.
In natsort
_ version 6.0.0, the following APIs and functions were removed
number_type
keyword argument (deprecated since 3.4.0)signed
keyword argument (deprecated since 3.4.0)exp
keyword argument (deprecated since 3.4.0)as_path
keyword argument (deprecated since 3.4.0)py3_safe
keyword argument (deprecated since 3.4.0)ns.TYPESAFE
(deprecated since version 5.0.0)ns.DIGIT
(deprecated since version 5.0.0)ns.VERSION
(deprecated since version 5.0.0)versorted()
(discouraged since version 4.0.0,
officially deprecated since version 5.5.0)index_versorted()
(discouraged since version 4.0.0,
officially deprecated since version 5.5.0)In general, if you want to determine if you are using deprecated APIs you can run your code with the following flag
.. code-block:: console
$ python -Wdefault::DeprecationWarning my-code.py
By default DeprecationWarnings
_ are not shown, but this will cause them
to be shown. Alternatively, you can just set the environment variable
PYTHONWARNINGS
to "default::DeprecationWarning" and then run your code.
Seth M. Morton
Please visit the changelog on GitHub
_.
.. _natsort: https://natsort.readthedocs.io/en/stable/index.html .. _natsorted(): https://natsort.readthedocs.io/en/stable/api.html#natsort.natsorted .. _natsort_keygen(): https://natsort.readthedocs.io/en/stable/api.html#natsort.natsort_keygen .. _realsorted(): https://natsort.readthedocs.io/en/stable/api.html#natsort.realsorted .. _humansorted(): https://natsort.readthedocs.io/en/stable/api.html#natsort.humansorted .. _os_sorted(): https://natsort.readthedocs.io/en/stable/api.html#natsort.os_sorted .. _the ns enum: https://natsort.readthedocs.io/en/stable/api.html#natsort.ns .. _fastnumbers: https://github.com/SethMMorton/fastnumbers .. _sorted(): https://docs.python.org/3/library/functions.html#sorted .. _list.sort(): https://docs.python.org/3/library/stdtypes.html#list.sort .. _key function: https://docs.python.org/3/howto/sorting.html#key-functions .. _locale: https://docs.python.org/3/library/locale.html .. _int: https://docs.python.org/3/library/functions.html#int .. _float: https://docs.python.org/3/library/functions.html#float .. _str: https://docs.python.org/3/library/stdtypes.html#str .. _bytes: https://docs.python.org/3/library/stdtypes.html#bytes .. _list: https://docs.python.org/3/library/stdtypes.html#list .. _tuple: https://docs.python.org/3/library/stdtypes.html#tuple .. _TypeError: https://docs.python.org/3/library/exceptions.html#TypeError .. _DeprecationWarnings: https://docs.python.org/3/library/exceptions.html#DeprecationWarning .. _"extras" notation: https://packaging.python.org/tutorials/installing-packages/#installing-setuptools-extras .. _PyICU: https://pypi.org/project/PyICU .. _tox: https://tox.readthedocs.io/en/latest/ .. _Examples and Recipes: https://github.com/SethMMorton/natsort/wiki/Examples-and-Recipes .. _How Does Natsort Work?: https://github.com/SethMMorton/natsort/wiki/How-Does-Natsort-Work%3F .. _API: https://natsort.readthedocs.io/en/stable/api.html .. _on GitHub: https://github.com/SethMMorton/natsort/blob/main/CHANGELOG.md .. _file an issue: https://github.com/SethMMorton/natsort/issues/new .. _look at this issue describing how to debug: https://github.com/SethMMorton/natsort/issues/13#issuecomment-50422375 .. _controlling the case-sensitivity: https://github.com/SethMMorton/natsort/wiki/Examples-and-Recipes#controlling-case-when-sorting .. _sorting file paths correctly: https://github.com/SethMMorton/natsort/wiki/Examples-and-Recipes#sort-os-generated-paths .. _allow custom sorting keys: https://github.com/SethMMorton/natsort/wiki/Examples-and-Recipes#using-a-custom-sorting-key .. _accounting for units: https://github.com/SethMMorton/natsort/wiki/Examples-and-Recipes#accounting-for-units-when-sorting .. _these version sorting examples: https://github.com/SethMMorton/natsort/wiki/Examples-and-Recipes#sorting-more-expressive-versioning-schemes .. _locale issues: https://github.com/SethMMorton/natsort/wiki/Possible-Issues-with-natsort.humansorted-or-ns.LOCALE .. _shell script wiki documentation: https://github.com/SethMMorton/natsort/wiki/Shell-Script