pelper - python helper functions

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pelper – python helper functions to ease measuring, ignoring, caching, piping, functional helpers, and more for python 2.7, 3.4, and 3.5.

pelper contains useful helper functions, decorators, context managers - all the things that make your python life a tiny bit easier. pelper has no dependencies, has a coverage of 100%, and is well documented.


Pipe data through unix-like/elixir-like pipes:

>>> from pelper import pipe
>>> pipe("some datat, some data", set, (sorted, {"reverse": True}))
['t', 's', 'o', 'm', 'e', 'd', 'a', ',', ' ']

Pelper offers p-functions, i.e., functions where the first argument is data. There is pmap (like map, but works with pipel):

>>> from pelper import pipe, pmap
>>> pipe(
...     range(5),
...     (pmap, lambda x: x*x),
...     list)
[0, 1, 4, 9, 16]

...and also pfilter:

>>> from pelper import pipe, pfilter
>>> pipe(
...     range(5),
...     (pfilter, lambda x: x > 2),
...     list)
[3, 4]

Take n elements from iterables (useful if you can’t use the square bracket notation, e.g., if you’re using pipe)

>>> from pelper import take
>>> take("hello world", 5)
['h', 'e', 'l', 'l', 'o']

Take the n-th elements from iterables (useful if you can’t use the square bracket notation, e.g., if you’re using pipe)

>>> from pelper import nth
>>> nth(range(5), 2)

Flatten arbitrarily nested lists:

>>> from pelper import flatten
>>> flatten([1, [2, 2, [3, 3]]])
[1, 2, 2, 3, 3]

Measure the duration of a function:

>>> from pelper import print_duration
>>> @print_duration()
...  def f(n): pass

Measure the duration of a context:

>>> from pelper import print_duration
>>> with print_duration():
...     range(4)

Ignore exceptions:

>>> from pelper import ignored
>>> with ignored(OSError):
...     raise OSError()  # this is ignored

Cache already computed results of functions:

>>> from pelper import cache
>>> @cache
>>> def fib(n):
...     return 1 if n < 2 else fib(n-1) + fib(n-2)
>>> f(500)  # this would run for quite a wile without the cache decorator

Easier printing and formating:

>>> from pelper import printf
>>> printf("Hello {name}, I'm {something}", name="Alan", something="world")
Hello Alan, I'm world


pelper is only one file and has no dependencies. You can simply drop into your project and use it.

Or install it from pypi by running:

pip install pelper

Or install it from source by running:

pip install .


Use virtualenv for working on pelper. Install the dev requrirements via:

pip install -e requirements-dev.txt


pelper uses doctest, py.test, and tox for testing. It also has Coverage status coverage.

You can run the tests for all supported versions of python and build and test the docs:


Run only the tests for the specified version of python:

tox -e py27,py34,py35

Alternatively just run tests for the current version of python:



Build the docs via:

cd docs
sphinx html

pelper functions

TODO add a list of functions.

TODO generate index etc

>>> 2 + 2

Indices and tables