ubelt 0.10.0

Timing

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.

Note: Timerit is also defined in a standalone module: pip install timerit)

>>> 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 no-threads attached Progress meter that writes to stdout. It 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 also defined in a standalone module: pip install 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

Caching

Cache intermediate results in a script with minimal boilerplate. It looks like 4 lines of boilerplate is the best you can do with Python 3.8 syntax. See <https://raw.githubusercontent.com/Erotemic/ubelt/master/ubelt/util_cache.py>`__ for details.

>>> 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
>>>     cacher.save(data)
>>> myvar1, myvar2 = data

Hashing

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]
5f5fda5e

There exists an undocumented plugin architecture to extend this function to arbitrary types. See ubelt/util_hash.py 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 verbose=True, ub.cmd will simultaneously capture the standard output and display it in real time.

>>> import ubelt as ub
>>> info = ub.cmd('gcc --version', verbose=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
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

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')))
~/.cache/my_app
>>> print(ub.compressuser(ub.ensure_app_resource_dir('my_app')))
~/.config/my_app

Symlinks

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

>>> import ubelt as ub
>>> url = 'http://i.imgur.com/rqwaDag.png'
>>> fpath = ub.download(url, verbose=0)
>>> print(ub.compressuser(fpath))
~/.cache/ubelt/rqwaDag.png

The function ub.grabdata works similarly to ub.download, but whereas ub.download 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 = 'http://i.imgur.com/rqwaDag.png'
>>> fpath = ub.grabdata(url, verbose=0, hash_prefix='944389a39')
>>> print(ub.compressuser(fpath))
~/.cache/ubelt/rqwaDag.png

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").

Grouping

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.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.expandpath('~/code/ubelt/ubelt'))
>>> print('module = {!r}'.format(module))
module = <module 'ubelt' from '/home/joncrall/code/ubelt/ubelt/__init__.py'>
>>> module = ub.import_module_from_name('ubelt')
>>> print('module = {!r}'.format(module))
module = <module 'ubelt' from '/home/joncrall/code/ubelt/ubelt/__init__.py'>

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/util_import.py).

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

External tools

Some of the tools in ubelt also exist as standalone modules. I haven’t decided if its best to statically copy them into ubelt or require on pypi to satisfy the dependency. There are some tools that are not used by default unless you explicitly allow for them.

Code that is currently statically included:

• ProgIter - https://github.com/Erotemic/progiter

• Timerit - https://github.com/Erotemic/timerit

Code that is currently linked via pypi:

• OrderedSet - https://github.com/LuminosoInsight/ordered-set

Code that is completely optional, and only used in specific cases:

• Numpy - ub.repr2 will format a numpy array nicely by default

• xxhash - this can be specified as a hasher to ub.hash_data

• Pygments - used by the util_color module.

Similar Tools

UBelt is one of many Python utility libraries. Other similar libraries are listed here:

• Boltons: https://github.com/mahmoud/boltons

• More-Itertools: https://pypi-hypernode.com/project/more-itertools/

• Toolz: https://github.com/pytoolz/toolz

• CyToolz: https://github.com/pytoolz/cytoolz/

• Funcy: https://github.com/Suor/funcy

Notes.

Ubelt will support Python 2.7 and 3.5 until the 1.0 release.

PRs are welcome.

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

• ProgIter https://github.com/Erotemic/progiter

• Timerit https://github.com/Erotemic/timerit

• mkinit https://github.com/Erotemic/mkinit

• xdoctest https://github.com/Erotemic/xdoctest

• xinspect https://github.com/Erotemic/xinspect

• xdev https://github.com/Erotemic/xdev

• vimtk https://github.com/Erotemic/vimtk

• graphid https://github.com/Erotemic/graphid

• ibeis https://github.com/Erotemic/ibeis

• kwarray https://github.com/Kitware/kwarray

• kwimage https://github.com/Kitware/kwimage

• kwcoco https://github.com/Kitware/kwcoco