Skip to content
A Python utility belt containing simple tools, a stdlib like feel, and extra batteries. Hashing, Caching, Timing, Progress, and more made easy!
Python Shell
Branch: master
Clone or download
Latest commit 3f9dcaf Jul 25, 2019
Type Name Latest commit message Commit time
Failed to load latest commit information.
.circleci Fix tests when only minimal dependencies are installed Mar 13, 2019
.github update pull request template Apr 27, 2019
dev moved script to dev dir May 13, 2019
requirements wip - Squashed 4 commits from <Sun, 03 Mar 2019 20:18:49 -0500> to <2… Mar 13, 2019
tests Fix bug in dict_subset and dict_hist Mar 19, 2019
ubelt add reference and note Jul 25, 2019
.gitattributes gitattributes Dec 26, 2017
.gitignore wip Mar 13, 2019
.travis.yml Fixed travis before install Mar 13, 2019 Messed up version update Jul 11, 2019
README.rst update logo to a banner May 27, 2019
appveyor.yml Refactor requirements Mar 13, 2019 Added to allow for network cmdline arg May 3, 2018 wip May 27, 2019
pytest.ini Moved symlinks to new file. Removed dependency on pywin32. Using wind… Feb 21, 2018
requirements.txt Allow for -r in requirements parsing Jul 11, 2019 tweaks Jul 11, 2019 Refactor requirements Mar 13, 2019 Allow for -r in requirements parsing Jul 11, 2019


CircleCI Travis Appveyor Codecov Pypi Downloads ReadTheDocs

Ubelt is a small library of robust, tested, documented, and simple functions that extend the Python standard library. You've probably written and re-written some of the functions in ubelt before (or wrote out the logic inline). Next time, try pip install ubelt instead.

  • Goal: provide simple functions that acomplish common tasks not yet addressed by the python standard library.
  • Constraints: Must be low-impact pure python; it should be easy to install and use.
  • Method: All functions are written with docstrings and doctests to ensure that a baseline level of documentation and testing always exists (even if functions are copy/pasted into other libraries)
  • Motto: Good utilities lift all codes.


UBelt is cross platform and all top-level functions behave similarly on Windows, Mac, and Linux (up to some small unavoidable differences). Almost every function in ubelt was written with a doctest. This provides helpful documentation and example usage as well as helping achieve 100% test coverage (sans Python2, Windows, stuff that could not be tested automatically, etc).

See the (Available Functions) section for detailed information.

Read the docs here:

Current Functionality

Ubelt is a currated collection of utilities.

UBelt's functionality is a mixture of the following categories:

  • Timing
  • Caching
  • Hashing
  • Command Line / Shell Interaction
  • Cross-Platform Cache, Config, and Data Directories
  • Symlinks
  • Downloading Files
  • Dictionary Histogram
  • Find Duplicates
  • Dictionary Manipulation
  • AutoDict - Autovivification
  • String-based imports
  • Horizontal String Concatenation
  • Standalone modules.


UBelt is written in pure Python and integrated into the python package index. Just pip install it and then import it!

From pypi:

pip install ubelt

From github:

pip install git+


UBelt is a "utility belt" of commonly needed utility and helper functions.

  • Reusable code - Many functions in ubelt are simple to write yourself (e.g. take, memoize, ensure_unicode), but even re-writing trivial functions takes time better spent on more important tasks. Rewriting has its place, but not when you can just pip install ubelt!
  • Easy access - The entire ubelt API is exposed at the top level. While the functions are defined in submodules, explicit imports make easy to access any function. There are also a small number of functions (e.g. ub.odict, ub.ddict, ub.flatten, which are aliases for collections.OrderedDict, collections.DefaultDict, and itertools.chain.from_iterable, respectively) that are essentially aliases for functions already in Python's standard library. I found myself using these functions so much that I wanted easier access to them, thus they are included in ubelt.
  • Extra batteries - Python's standard library is "batteries included" and provides great APIs for a variety of tasks. UBelt both extends these batteries and provides simplified interfaces to others.
  • Copy paste - It is often not desirable to add extra dependencies to code. While I encourage installation and use of this module, I realize that option is not always feasible. Most (but not all) functions were also written in a way where they can be copy and pasted into your packages own utility library without needing to add a dependency on ubelt.


UBelt is a migration of the most useful parts of utool( into a standalone module with minimal dependencies.

The utool library contains a number of useful utility functions, but it also contained non-useful functions, as well as the kitchen sink. A number of the functions were too specific or not well documented. The ubelt packages was created to is to slowly port over the most re-usable parts of utool into a stable package.

The doctest harness in utool was ported and rewritten in a new module called: `xdoctest <>`__, which integrates with pytest as a plugin. All of the doctests in ubelt are run using xdoctest.

A small subset of the static-analysis and code introspection tools in xdoctest are made visible through ubelt.

Available Functions:

Be sure to checkout the new Jupyter notebook:

For the following functions, see corresponding doc-strings for more details.

Some of the more interesting and useful functions and classes implemented are:

import ubelt as ub

ub.Timerit  # powerful multiline alternative to timeit
ub.Cacher  # configuration based on-disk cachine
ub.cmd  # combines the best of subprocess.Popen and os.system
ub.hash_data  # extremely useful with Cacher to config strings
ub.modname_to_modpath  # (works via static analysis)
ub.modpath_to_modname  # (works via static analysis)
ub.import_module_from_path  # (Unlike importlib, this does not break pytest)
ub.import_module_from_name  # (Unlike importlib, this does not break pytest)

A complete list of available functions can be seen in the ubelt/ file, which was auto-generated by mkinit(

from ubelt.util_arg import (argflag, argval,)
from ubelt.util_cache import (CacheStamp, Cacher,)
from ubelt.util_colors import (color_text, highlight_code,)
from ubelt.util_const import (NoParam,)
from ubelt.util_cmd import (cmd,)
from ubelt.util_dict import (AutoDict, AutoOrderedDict, ddict, dict_diff,
                             dict_hist, dict_isect, dict_subset, dict_take,
                             dict_union, dzip, find_duplicates, group_items,
                             invert_dict, map_keys, map_vals, odict,)
from ubelt.util_download import (download, grabdata,)
from ubelt.util_func import (identity, inject_method,)
from ubelt.util_format import (FormatterExtensions, repr2,)
from ubelt.util_io import (delete, readfrom, touch, writeto,)
from ubelt.util_links import (symlink,)
from ubelt.util_list import (allsame, argmax, argmin, argsort, argunique,
                             boolmask, chunks, compress, flatten, iter_window,
                             iterable, peek, take, unique, unique_flags,)
from ubelt.util_hash import (hash_data, hash_file,)
from ubelt.util_import import (import_module_from_name,
                               import_module_from_path, modname_to_modpath,
                               modpath_to_modname, split_modpath,)
from ubelt.util_memoize import (memoize, memoize_method, memoize_property,)
from ubelt.util_mixins import (NiceRepr,)
from ubelt.util_path import (TempDir, augpath, compressuser, ensuredir,
                             expandpath, truepath, userhome,)
from ubelt.util_platform import (DARWIN, LINUX, POSIX, WIN32, editfile,
                                 ensure_app_cache_dir, ensure_app_config_dir,
                                 ensure_app_data_dir, ensure_app_resource_dir,
                                 find_exe, find_path, get_app_cache_dir,
                                 get_app_config_dir, get_app_data_dir,
                                 get_app_resource_dir, platform_cache_dir,
                                 platform_config_dir, platform_data_dir,
                                 platform_resource_dir, startfile,)
from ubelt.util_str import (codeblock, ensure_unicode, hzcat, indent,
from ubelt.util_stream import (CaptureStdout, CaptureStream, TeeStringIO,)
from ubelt.util_time import (Timer, Timerit, timestamp,)
from ubelt.orderedset import (OrderedSet, oset,)
from ubelt.progiter import (ProgIter,)


Here are some examples of some features inside ubelt


Quickly time a single line.

>>> import math
>>> import ubelt as ub
>>> timer = ub.Timer('Timer demo!', verbose=1)
>>> with timer:
>>>     math.factorial(100000)
tic('Timer demo!')
...toc('Timer demo!')=0.1453s

Robust Timing and Benchmarking

Easily do robust timings on existing blocks of code by simply indenting them. There is no need to refactor into a string representation or convert to a single line. With ub.Timerit there is no need to resort to the timeit module!

The quick and dirty way just requires one indent.

>>> import math
>>> import ubelt as ub
>>> for _ in ub.Timerit(num=200, verbose=3):
>>>     math.factorial(10000)
Timing for 200 loops
Timed for: 200 loops, best of 3
    time per loop: best=2.055 ms, mean=2.145 ± 0.083 ms

Use the loop variable as a context manager for more accurate timings or to incorporate an setup phase that is not timed. You can also access properties of the ub.Timerit class to programmatically use results.

>>> import math
>>> import ubelt as ub
>>> t1 = ub.Timerit(num=200, verbose=2)
>>> for timer in t1:
>>>     setup_vars = 10000
>>>     with timer:
>>>         math.factorial(setup_vars)
>>> print('t1.total_time = %r' % (t1.total_time,))
Timing for 200 loops
Timed for: 200 loops, best of 3
    time per loop: best=2.064 ms, mean=2.115 ± 0.05 ms
t1.total_time = 0.4427177629695507

Loop Progress

ProgIter is a (mostly) drop-in alternative to `tqdm <>`__. The advantage of ``ProgIter`` is that it does not use any python threading, and therefore can be safer with code that makes heavy use of multiprocessing.

Note: ProgIter is now a standalone module: pip intstall progiter)

>>> import ubelt as ub
>>> def is_prime(n):
...     return n >= 2 and not any(n % i == 0 for i in range(2, n))
>>> for n in ub.ProgIter(range(1000), verbose=2):
>>>     # do some work
>>>     is_prime(n)
    0/1000... rate=0.00 Hz, eta=?, total=0:00:00, wall=14:05 EST
    1/1000... rate=82241.25 Hz, eta=0:00:00, total=0:00:00, wall=14:05 EST
  257/1000... rate=177204.69 Hz, eta=0:00:00, total=0:00:00, wall=14:05 EST
  642/1000... rate=94099.22 Hz, eta=0:00:00, total=0:00:00, wall=14:05 EST
 1000/1000... rate=71886.74 Hz, eta=0:00:00, total=0:00:00, wall=14:05 EST


Cache intermediate results in a script with minimal boilerplate.

>>> import ubelt as ub
>>> cfgstr = 'repr-of-params-that-uniquely-determine-the-process'
>>> cacher = ub.Cacher('test_process', cfgstr)
>>> data = cacher.tryload()
>>> if data is None:
>>>     myvar1 = 'result of expensive process'
>>>     myvar2 = 'another result'
>>>     data = myvar1, myvar2
>>> myvar1, myvar2 = data


The ub.hash_data constructs a hash corresponding to a (mostly) arbitrary ordered python object. A common use case for this function is to construct the cfgstr mentioned in the example for ub.Cacher. Instead of returning a hex, string, ub.hash_data encodes the hash digest using the 26 lowercase letters in the roman alphabet. This makes the result easy to use as a filename suffix.

>>> import ubelt as ub
>>> data = [('arg1', 5), ('lr', .01), ('augmenters', ['flip', 'translate'])]
>>> ub.hash_data(data)[0:8]

There exists an undocumented plugin architecture to extend this function to arbitrary types. See ubelt/ for details.

Command Line Interaction

The builtin Python subprocess.Popen module is great, but it can be a bit clunky at times. The os.system command is easy to use, but it doesn't have much flexibility. The ub.cmd function aims to fix this. It is as simple to run as os.system, but it returns a dictionary containing the return code, standard out, standard error, and the Popen object used under the hood.

>>> import ubelt as ub
>>> info = ub.cmd('gcc --version')
>>> print(ub.repr2(info))
    'command': 'gcc --version',
    'err': '',
    'out': 'gcc (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609\nCopyright (C) 2015 Free Software Foundation, Inc.\nThis is free software; see the source for copying conditions.  There is NO\nwarranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\n',
    'proc': <subprocess.Popen object at 0x7ff98b310390>,
    'ret': 0,

Also note the use of ub.repr2 to nicely format the output dictionary.

Additionally, if you specify verbout=True, ub.cmd will simultaneously capture the standard output and display it in real time.

>>> import ubelt as ub
>>> info = ub.cmd('gcc --version', verbout=True)
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO

A common use case for ub.cmd is parsing version numbers of programs

>>> import ubelt as ub
>>> cmake_version = ub.cmd('cmake --version')['out'].splitlines()[0].split()[-1]
>>> print('cmake_version = {!r}'.format(cmake_version))
cmake_version = 3.11.0-rc2

This allows you to easily run a command line executable as part of a python process, see what it is doing, and then do something based on its output, just as you would if you were interacting with the command line itself.

Lastly, ub.cmd removes the need to think about if you need to pass a list of args, or a string. Both will work. This utility has been tested on both Windows and Linux.

Cross-Platform Resource and Cache Directories

If you have an application which writes configuration or cache files, the standard place to dump those files differs depending if you are on Windows, Linux, or Mac. UBelt offers a unified functions for determining what these paths are.

The ub.ensure_app_cache_dir and ub.ensure_app_resource_dir functions find the correct platform-specific location for these files and ensures that the directories exist. (Note: replacing "ensure" with "get" will simply return the path, but not ensure that it exists)

The resource root directory is ~/AppData/Roaming on Windows, ~/.config on Linux and ~/Library/Application Support on Mac. The cache root directory is ~/AppData/Local on Windows, ~/.config on Linux and ~/Library/Caches on Mac.

Example usage on Linux might look like this:

>>> import ubelt as ub
>>> print(ub.compressuser(ub.ensure_app_cache_dir('my_app')))
>>> print(ub.compressuser(ub.ensure_app_resource_dir('my_app')))


The ub.symlink function will create a symlink similar to os.symlink. The main differences are that 1) it will not error if the symlink exists and already points to the correct location. 2) it works* on Windows (*hard links and junctions are used if real symlinks are not available)

>>> import ubelt as ub
>>> dpath = ub.ensure_app_cache_dir('ubelt', 'demo_symlink')
>>> real_path = join(dpath, 'real_file.txt')
>>> link_path = join(dpath, 'link_file.txt')
>>> ub.writeto(real_path, 'foo')
>>> ub.symlink(real_path, link_path)

Downloading Files

The function provides a simple interface to download a URL and save its data to a file.

>>> import ubelt as ub
>>> url = ''
>>> fpath =, verbose=0)
>>> print(ub.compressuser(fpath))

The function ub.grabdata works similarly to, but whereas will always re-download the file, ub.grabdata will check if the file exists and only re-download it if it needs to.

>>> import ubelt as ub
>>> url = ''
>>> fpath = ub.grabdata(url, verbose=0, hash_prefix='944389a39')
>>> print(ub.compressuser(fpath))

New in version 0.4.0: both functions now accepts the hash_prefix keyword argument, which if specified will check that the hash of the file matches the provided value. The hasher keyword argument can be used to change which hashing algorithm is used (it defaults to "sha512").


Group items in a sequence into a dictionary by a second id list

>>> import ubelt as ub
>>> item_list    = ['ham',     'jam',   'spam',     'eggs',    'cheese', 'bannana']
>>> groupid_list = ['protein', 'fruit', 'protein',  'protein', 'dairy',  'fruit']
>>> ub.group_items(item_list, groupid_list)
{'dairy': ['cheese'], 'fruit': ['jam', 'bannana'], 'protein': ['ham', 'spam', 'eggs']}

Dictionary Histogram

Find the frequency of items in a sequence

>>> import ubelt as ub
>>> item_list = [1, 2, 39, 900, 1232, 900, 1232, 2, 2, 2, 900]
>>> ub.dict_hist(item_list)
{1232: 2, 1: 1, 2: 4, 900: 3, 39: 1}

Find Duplicates

Find all duplicate items in a list. More specifically, ub.find_duplicates searches for items that appear more than k times, and returns a mapping from each duplicate item to the positions it appeared in.

>>> import ubelt as ub
>>> items = [0, 0, 1, 2, 3, 3, 0, 12, 2, 9]
>>> ub.find_duplicates(items, k=2)
{0: [0, 1, 6], 2: [3, 8], 3: [4, 5]}

Dictionary Manipulation

Take a subset of a dictionary.

>>> import ubelt as ub
>>> dict_ = {'K': 3, 'dcvs_clip_max': 0.2, 'p': 0.1}
>>> subdict_ = ub.dict_subset(dict_, ['K', 'dcvs_clip_max'])
>>> print(subdict_)
{'K': 3, 'dcvs_clip_max': 0.2}

Take only the values, optionally specify a default value.

>>> import ubelt as ub
>>> dict_ = {1: 'a', 2: 'b', 3: 'c'}
>>> print(list(ub.dict_take(dict_, [1, 2, 3, 4, 5], default=None)))
['a', 'b', 'c', None, None]

Apply a function to each value in the dictionary (see also ub.map_keys).

>>> import ubelt as ub
>>> dict_ = {'a': [1, 2, 3], 'b': []}
>>> newdict = ub.map_vals(len, dict_)
>>> print(newdict)
{'a': 3, 'b': 0}

Invert the mapping defined by a dictionary. By default invert_dict assumes that all dictionary values are distinct (i.e. the mapping is one-to-one / injective).

>>> import ubelt as ub
>>> mapping = {0: 'a', 1: 'b', 2: 'c', 3: 'd'}
>>> ub.invert_dict(mapping)
{'a': 0, 'b': 1, 'c': 2, 'd': 3}

However, by specifying unique_vals=False the inverted dictionary builds a set of keys that were associated with each value.

>>> import ubelt as ub
>>> mapping = {'a': 0, 'A': 0, 'b': 1, 'c': 2, 'C': 2, 'd': 3}
>>> ub.invert_dict(mapping, unique_vals=False)
{0: {'A', 'a'}, 1: {'b'}, 2: {'C', 'c'}, 3: {'d'}}

AutoDict - Autovivification

While the collections.defaultdict is nice, it is sometimes more convenient to have an infinitely nested dictionary of dictionaries.

>>> import ubelt as ub
>>> auto = ub.AutoDict()
>>> print('auto = {!r}'.format(auto))
auto = {}
>>> auto[0][10][100] = None
>>> print('auto = {!r}'.format(auto))
auto = {0: {10: {100: None}}}
>>> auto[0][1] = 'hello'
>>> print('auto = {!r}'.format(auto))
auto = {0: {1: 'hello', 10: {100: None}}}

String-based imports

Ubelt contains functions to import modules dynamically without using the python import statement. While importlib exists, the ubelt implementation is simpler to user and does not have the disadvantage of breaking pytest.

Note ubelt simply provides an interface to this functionality, the core implementation is in xdoctest (over as of version 0.7.0, the code is statically copied into an autogenerated file such that ubelt does not actually depend on xdoctest during runtime).

>>> import ubelt as ub
>>> module = ub.import_module_from_path(ub.truepath('~/code/ubelt/ubelt'))
>>> print('module = {!r}'.format(module))
module = <module 'ubelt' from '/home/joncrall/code/ubelt/ubelt/'>
>>> module = ub.import_module_from_name('ubelt')
>>> print('module = {!r}'.format(module))
module = <module 'ubelt' from '/home/joncrall/code/ubelt/ubelt/'>

Related to this functionality are the functions ub.modpath_to_modname and ub.modname_to_modpath, which statically transform (i.e. no code in the target modules is imported or executed) between module names (e.g. ubelt.util_import) and module paths (e.g. ~/.local/conda/envs/cenv3/lib/python3.5/site-packages/ubelt/

>>> import ubelt as ub
>>> modpath = ub.util_import.__file__
>>> print(ub.modpath_to_modname(modpath))
>>> modname = ub.util_import.__name__
>>> assert ub.truepath(ub.modname_to_modpath(modname)) == modpath

Horizontal String Concatenation

Sometimes its just prettier to horizontally concatenate two blocks of text.

>>> import ubelt as ub
>>> B = ub.repr2([[1, 2], [3, 4]], nl=1, cbr=True, trailsep=False)
>>> C = ub.repr2([[5, 6], [7, 8]], nl=1, cbr=True, trailsep=False)
>>> print(ub.hzcat(['A = ', B, ' * ', C]))
A = [[1, 2], * [[5, 6],
     [3, 4]]    [7, 8]]

Standalone tools.

Some of the tools in ubelt have been / are being ported to standalone modules. These tools will remain exposed in ubelt, so you have all the extra batteries at your disposal, but they will eventually just be added as simple dependencies and the source code will be removed from ubelt.

Here are the repos containing the standalone class utilities:


Ubelt will support Python2 for the forseeable future (at least until everyone I work with is off it followed by a probation period).

PRs are welcome. If you have a utility function that you think is useful then write a PR. I'm likely to respond promptly.

Also check out my other projects (many of which are powered by ubelt):

You can’t perform that action at this time.