Sort lists naturally

## Project description

Natural sorting for python. `natsort` requires python version 2.6 or greater
(this includes python 3.x). To run version 2.6, 3.1, or 3.2 the
argparse module is required.

`natsort` comes with a shell script that is described below. You can
also execute `natsort` from the command line with `python -m natsort`.

There exists another natural sorting package for python called naturalsort. You may prefer this package if you wish to only sort version numbers.

## Problem Statement

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:

>>> a = ['a2', 'a9', 'a1', 'a4', 'a10'] >>> sorted(a) ['a1', 'a10', 'a2', 'a4', 'a9']

Notice that it has the order (‘1’, ‘10’, ‘2’) - this is because the list is being sorted in lexicographically order, which sorts numbers like you would letters (i.e. ‘a’, ‘at’, ‘b’). It would be better if you had a sorting algorithm that recognized numbers as numbers and treated them like numbers, not letters.

This is where `natsort` comes in: it provides a key that helps sort lists
“naturally”. It provides support for ints and floats (including negatives and
exponential notation) that you can turn off to support sorting version numbers.

## Synopsis

Using `natsort` is simple:

>>> from natsort import natsorted >>> a = ['a2', 'a9', 'a1', 'a4', 'a10'] >>> natsorted(a) ['a1', 'a2', 'a4', 'a9', 'a10']

`natsort` identifies the numbers and sorts them separately from strings.

You can also mix and match `int`, `float`, and `str` (or `unicode`) types
when you sort:

>>> a = ['4.5', 6, 2.3, '5'] >>> natsorted(a) [2.3, '4.5', '5', 6] >>> # On Python 2, sorted(a) would return [2.3, 6, '4.5', '5'] >>> # On Python 3, sorted(a) would raise an "unorderable types" TypeError

### The Sorting Algorithms

Sometimes you want to sort by floats, sometimes by ints, and sometimes simply
by digits. `natsort` supports all three number types. They can be chosen
with the `number_type` argument to `natsorted`.

#### Sort by floats

By default, `natsort` searches for floats (even in exponential
notation!). This means that it will look for things like negative
signs and decimal points when determining a number:

>>> a = ['a50', 'a51.', 'a50.4', 'a5.034e1', 'a50.300'] >>> sorted(a) ['a5.034e1', 'a50', 'a50.300', 'a50.4', 'a51.'] >>> natsorted(a, number_type=float) ['a50', 'a50.300', 'a5.034e1', 'a50.4', 'a51.'] >>> natsorted(a) # Float is the default behavior ['a50', 'a50.300', 'a5.034e1', 'a50.4', 'a51.']

#### Sort by ints

In some cases you don’t want `natsort` to identify your numbers as floats,
particularly if you are sorting version numbers. This is because you want the
version ‘1.10’ to come after ‘1.2’, not before. In that case, it is advantageous
to sort by ints, not floats:

>>> a = ['ver1.9.9a', 'ver1.11', 'ver1.9.9b', 'ver1.11.4', 'ver1.10.1'] >>> sorted(a) ['ver1.10.1', 'ver1.11', 'ver1.11.4', 'ver1.9.9a', 'ver1.9.9b'] >>> natsorted(a) ['ver1.10.1', 'ver1.11', 'ver1.11.4', 'ver1.9.9a', 'ver1.9.9b'] >>> natsorted(a, number_type=int) ['ver1.9.9a', 'ver1.9.9b', 'ver1.10.1', 'ver1.11', 'ver1.11.4']

#### Sort by digits (best for version numbers)

The only difference between sorting by ints and sorting by digits is that
sorting by ints may take into account a negative sign, and sorting by digits
will not. This may be an issue if you used a ‘-‘ as your separator before the
version numbers. Essentially this is a shortcut for a number type of `int`
and the `signed` option of `False`:

>>> a = ['ver-2.9.9a', 'ver-1.11', 'ver-2.9.9b', 'ver-1.11.4', 'ver-1.10.1'] >>> natsorted(a, number_type=int) ['ver-2.9.9a', 'ver-2.9.9b', 'ver-1.10.1', 'ver-1.11', 'ver-1.11.4'] >>> natsorted(a, number_type=None) ['ver-1.10.1', 'ver-1.11', 'ver-1.11.4', 'ver-2.9.9a', 'ver-2.9.9b']

### Using a sorting key

Like the built-in `sorted` function, `natsorted` can accept a key so that
you can sort based on a particular item of a list or by an attribute of a class:

>>> from operator import attrgetter, itemgetter >>> a = [['num4', 'b'], ['num8', 'c'], ['num2', 'a']] >>> natsorted(a, key=itemgetter(0)) [['num2', 'a'], ['num4', 'b'], ['num8', 'c']] >>> class Foo: ... def __init__(self, bar): ... self.bar = bar ... def __repr__(self): ... return "Foo('{0}')".format(self.bar) >>> b = [Foo('num3'), Foo('num5'), Foo('num2')] >>> natsorted(b, key=attrgetter('bar')) [Foo('num2'), Foo('num3'), Foo('num5')]

## API

The `natsort` package provides three functions: `natsort_key`,
`natsorted`, and `index_natsorted`.

### natsorted

`natsort.natsorted` (*sequence*, *key* = `lambda x: x`, *number_type* = `float`, *signed* = `True`, *exp* = `True`)

- sequence (
iterable)- The sequence to sort.
- key (
function)- A key used to determine how to sort each element of the sequence.
- number_type (
None,float,int)- The types of number to sort by:
floatsearches for floating point numbers,intsearches for integers, andNonesearches for digits (like integers but does not take into account negative sign).Noneis a shortcut fornumber_type = intandsigned = False.- signed (
True,False)- By default a ‘+’ or ‘-‘ before a number is taken to be the sign of the number. If
signedisFalse, any ‘+’ or ‘-‘ will not be considered to be part of the number, but as part of the string.- exp (
True,False)- This option only applies to
number_type = float. Ifexp = True, a string like"3.5e5"will be interpreted as350000, i.e. the exponential part is considered to be part of the number. Ifexp = False,"3.5e5"is interpreted as(3.5, "e", 5). The default behavior isexp = True.- returns
- The sorted sequence.

Use `natsorted` just like the builtin `sorted`:

>>> from natsort import natsorted >>> a = ['num3', 'num5', 'num2'] >>> natsorted(a) ['num2', 'num3', 'num5']

### natsort_key

`natsort.natsort_key` (value, *number_type* = `float`, *signed* = `True`, *exp* = `True`)

- value
- The value used by the sorting algorithm
- number_type (
None,float,int)- The types of number to sort on:
floatsearches for floating point numbers,intsearches for integers, andNonesearches for digits (like integers but does not take into account negative sign).Noneis a shortcut fornumber_type = intandsigned = False.- signed (
True,False)- By default a ‘+’ or ‘-‘ before a number is taken to be the sign of the number. If
signedisFalse, any ‘+’ or ‘-‘ will not be considered to be part of the number, but as part part of the string.- exp (
True,False)- This option only applies to
number_type = float. Ifexp = True, a string like"3.5e5"will be interpreted as350000, i.e. the exponential part is considered to be part of the number. Ifexp = False,"3.5e5"is interpreted as(3.5, "e", 5). The default behavior isexp = True.- returns
- The modified value with numbers extracted.

Using `natsort_key` is just like any other sorting key in python:

>>> from natsort import natsort_key >>> a = ['num3', 'num5', 'num2'] >>> a.sort(key=natsort_key) >>> a ['num2', 'num3', 'num5']

If you need to call `natsort_key` with the `number_type` argument, or get a special
attribute or item of each element of the sequence, the easiest way is to make a
`lambda` expression that calls `natsort_key`:

>>> from operator import itemgetter >>> a = [['num4', 'b'], ['num8', 'c'], ['num2', 'a']] >>> f = itemgetter(0) >>> a.sort(key=lambda x: natsort_key(f(x), number_type=int)) >>> a [['num2', 'a'], ['num4', 'b'], ['num8', 'c']]

### index_natsorted

`natsort.index_natsorted` (*sequence*, *key* = `lambda x: x`, *number_type* = `float`, *signed* = `True`, *exp* = `True`)

- sequence (
iterable)- The sequence to sort.
- key (
function)- A key used to determine how to sort each element of the sequence.
- number_type (
None,float,int)- The types of number to sort on:
floatsearches for floating point numbers,intsearches for integers, andNonesearches for digits (like integers but does not take into account negative sign).Noneis a shortcut fornumber_type = intandsigned = False.- signed (
True,False)- By default a ‘+’ or ‘-‘ before a number is taken to be the sign of the number. If
signedisFalse, any ‘+’ or ‘-‘ will not be considered to be part of the number, but as part part of the string.- exp (
True,False)- This option only applies to
number_type = float. Ifexp = True, a string like"3.5e5"will be interpreted as350000, i.e. the exponential part is considered to be part of the number. Ifexp = False,"3.5e5"is interpreted as(3.5, "e", 5). The default behavior isexp = True.- returns
- The ordered indexes of the sequence.

Use `index_natsorted` if you want to sort multiple lists by the sort order of
one list:

>>> from natsort import index_natsorted >>> a = ['num3', 'num5', 'num2'] >>> b = ['foo', 'bar', 'baz'] >>> index = index_natsorted(a) >>> index [2, 0, 1] >>> # Sort both lists by the sort order of a >>> [a[i] for i in index] ['num2', 'num3', 'num5'] >>> [b[i] for i in index] ['baz', 'foo', 'bar']

## Shell Script

For your convenience, there is a `natsort` shell script supplied to you that
allows you to call `natsort` from the command-line. `natsort` was written to
aid in computational chemistry research so that it would be easy to analyze
large sets of output files named after the parameter used:

$ ls *.out mode1000.35.out mode1243.34.out mode744.43.out mode943.54.out

(Obviously, in reality there would be more files, but you get the idea.) Notice
that the shell sorts in lexicographical order. This is the behavior of programs like
`find` as well as `ls`. The problem is in passing these files to an
analysis program that causes them not to appear in numerical order, which can lead
to bad analysis. To remedy this, use `natsort`:

# This won't get you what you want $ foo *.out # This will sort naturally $ natsort *.out mode744.43.out mode943.54.out mode1000.35.out mode1243.34.out $ natsort *.out | xargs foo

You can also filter out numbers using the `natsort` command-line script:

$ natsort *.out -f 900 1100 # Select only numbers between 900-1100 mode943.54.out mode1000.35.out

If needed, you can exclude specific numbers:

$ natsort *.out -e 1000.35 # Exclude 1000.35 from search mode744.43.out mode943.54.out mode1243.34.out

For other options, use `natsort --help`. In general, the other options mirror
the `natsorted` API.

It is also helpful to note that `natsort` accepts pipes.

### Note to users of the `natsort` shell script from < v. 3.1.0

The `natsort` shell script options and implementation for version 3.1.0 has
changed slightly. Options relating to interpreting input as file or directory
paths have been removed, and internally the input is no longer treated as file
paths. In most situations, this should not give different results, but in
some unique cases it may. Feel free to contact me if this ruins your work flow.

## History

### 01-20-2014 v. 3.1.0

Added the

signedandexpoptions to allow finer tuning of the sortingEntire codebase now works for both Python 2 and Python 3 without needing to run

2to3.Updated all doctests.

Further simplified the

natsortbase code by removing unneeded functions.Simplified documentation where possible.

Improved the shell script code

- Made the documentation less “path”-centric to make it clear it is not just for sorting file paths.
- Removed the filesystem-based options because these can be achieved better though a pipeline.
- Added doctests.
- Added new options that correspond to
signedandexp.- The user can now specify multiple numbers to exclude or multiple ranges to filter by.

### 10-01-2013 v. 3.0.2

- Made float, int, and digit searching algorithms all share the same base function
- Fixed some outdated comments
- Made the
__version__variable available when importing the module

### 8-15-2013 v. 3.0.1

- Added support for unicode strings.
- Removed extraneous
string2intfunction.- Fixed empty string removal function.

### 7-13-2013 v. 3.0.0

- Added a
number_typeargument to the sorting functions to specify how liberal to be when deciding what a number is.- Reworked the documentation.

### 6-25-2013 v. 2.2.0

- Added
keyattribute tonatsortedandindex_natsortedso that it mimics the functionality of the built-insorted- Added tests to reflect the new functionality, as well as tests demonstrating how to get similar functionality using
natsort_key.

### 12-5-2012 v. 2.1.0

- Reorganized package
- Now using a platform independent shell script generator (entry_points from distribute)
- Can now execute natsort from command line with
python -m natsortas well

### 11-30-2012 v. 2.0.2

- Added the use_2to3 option to setup.py
- Added distribute_setup.py to the distribution
- Added dependency to the argparse module (for python2.6)

### 11-21-2012 v. 2.0.1

- Reorganized directory structure
- Added tests into the natsort.py file iteself

### 11-16-2012, v. 2.0.0

- Updated sorting algorithm to support floats (including exponentials) and basic version number support
- Added better README documentation
- Added doctests

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