ebbe 1.15.1

Collection of typical helper functions for python.

Ebbe

A collection of typical helper functions for python that cannot be found in the however great standard library.

Installation

You can install ebbe with pip with the following command:

pip install ebbe

Usage

Iterator functions

• as_chunks
• as_reconciled_chunks
• outer_zip
• as_grams
• fail_fast
• uniq
• distinct
• with_prev
• with_prev_and_next
• with_next
• with_is_first
• with_is_last
• without_first
• without_last

Utilities

• get
• getter
• getpath
• pathgetter
• indexed
• grouped
• partitioned
• sorted_uniq
• pick
• omit

Functional Programming

• noop
• compose
• rcompose

Formatting

• and_join
• format_int
• format_time

TODO: format_repr, format_filesize

Decorators

• decorators.fail_fast
• decorators.with_defer

Benchmarking

• Timer

as_chunks

Iterate over chunks of the desired size by grouping items as we iterate over them.

from ebbe import as_chunks

list(as_chunks(3, [1, 2, 3, 4, 5]))
>>> [[1, 2, 3], [4, 5]]

as_reconciled_chunks

Iterate over chunks of the desired size by grouping items as we iterate over them, then call a function returning some result for a given chunk, then "reconcile" chunk items using another function to finally produce a flat iterator over original values along with the associated result.

from ebbe import as_reconciled_chunks

data = [1, 2, 3, 4, 5, 6]

def work(chunk):
    return {n: True for n in chunk if n % 2 == 0}

def reconcile(data, item):
    return data.get(item)

list(as_reconciled_chunks(3, data, work, reconcile))
>>> [(1, None), (2, True), (3, None), (4, True), (5, None), (6, True)]

outer_zip

Iterate over an iterator from which one must extract a key to work on to produce a resulting iterator all while keeping a reference to the original item in the output.

Note that this function only produces a correct output if:

1. work done is single-threaded (this function is absolutely not threadsafe)
2. the work function emits resulting items in the same order they are consumed from the input

from ebbe import outer_zip

data = [("one", 1), ("two", 2), ("three", 3)]

def work(numbers: Iterator[int]) -> Iterator[int]:
  for n in numbers:
    yield n * 2

list(
  (original_item[0], result)
  for original_item, result in outer_zip(data, key=lambda p: p[1], work=work)
)
>>> [("one", 2), ("two", 4), ("three", 6)]

as_grams

Iterate over grams (sometimes called n-grams or q-grams etc.) of the given iterable. It works with strings, lists and other sized sequences as well as with lazy iterables without consuming any superfluous memory while doing so.

from ebbe import as_grams

list(as_grams(3, 'hello'))
>>> ['hel', 'ell', 'llo']

list(as_grams(2, (i * 2 for i in range(5))))
>>> [(0, 2), (2, 4), (4, 6), (6, 8)]

fail_fast

Take an iterable (but this has been geared towards generators, mostly), and tries to access the first value to see if an Exception will be raised before returning an equivalent iterator.

This is useful with some badly-conceived generators that checks arguments and raise if they are not valid, for instance, and if you don't want to wrap the whole iteration block within a try/except.

This logic is also available as a decorator.

from ebbe import fail_fast

def hellraiser(n):
  if n > 10:
    raise TypeError

  yield from range(n)

# You will need to do this to catch the error:
gen = hellraiser(15)

try:
  for i in gen:
    print(i)
except TypeError:
  print('Something went wrong when creating the generator')

# With fail_fast
try:
  gen = fail_fast(hellraiser(15))
except TypeError:
  print('Something went wrong when creating the generator')

for i in gen:
  print(i)

uniq

Filter repeated items, optionally by key, seen next to each other in the given iterator.

from ebbe import uniq

list(uniq([1, 1, 1, 2, 3, 4, 4, 5, 5, 6]))
>>> [1, 2, 3, 4, 5, 6]

# BEWARE: it does not try to remember items (like the `uniq` command)
list(uniq([1, 2, 2, 3, 2]))
>>> [1, 2, 3, 2]

# Using a key
list(uniq([(1, 2), (1, 3), (2, 4)], key=lambda x: x[0]))
>>> [(1, 2), (2, 4)]

distinct

Filter repeated items, optionally by key, in the given iterator.

from ebbe import distinct

list(distinct([0, 3, 4, 4, 1, 0, 3]))
>>> [0, 3, 4, 1]

list(distinct(range(6), key=lambda x: x % 2))
>>> [0, 1]

with_prev

Iterate over items along with the previous one.

from ebbe import with_prev

for previous_item, item in with_prev(iterable):
  print(previous_item, 'came before', item)

list(with_prev([1, 2, 3]))
>>> [(None, 1), (1, 2), (2, 3)]

with_prev_and_next

Iterate over items along with the previous and the next one.

from ebbe import with_prev_and_next

for previous_item, item, next_item in with_prev_and_next(iterable):
  print(previous_item, 'came before', item)
  print(next_item, 'will come after', item)

list(with_prev_and_next([1, 2, 3]))
>>> [(None, 1, 2), (1, 2, 3), (2, 3, None)]

with_next

Iterate over items along with the next one.

from ebbe import with_next

for item, next_item in with_next(iterable):
  print(next_item, 'will come after', item)

list(with_next([1, 2, 3]))
>>> [(1, 2), (2, 3), (3, None)]

with_is_first

Iterate over items along with the information that the current item is the first one or not.

from ebbe import with_is_first

for is_first, item in with_is_first(iterable):
  if is_first:
    print(item, 'is first')
  else:
    print(item, 'is not first')

list(with_is_first([1, 2, 3]))
>>> [(True, 1), (False, 2), (False, 3)]

with_is_last

Iterate over items along with the information that the current item is the last one or not.

from ebbe import with_is_last

for is_last, item in with_is_last(iterable):
  if is_last:
    print(item, 'is last')
  else:
    print(item, 'is not last')

list(with_is_last([1, 2, 3]))
>>> [(False, 1), (False, 2), (True, 3)]

without_first

Iterate over the given iterator after skipping its first item. Can be useful if you want to skip headers of a CSV file for instance.

from ebbe import without_first

list(without_first([1, 2, 3]))
>>> [2, 3]

for row in without_first(csv.reader(f)):
  print(row)

without_last

Iterate over the given iterator but skipping its last item.

from ebbe import without_last

list(without_last([1, 2, 3]))
>>> [1, 2]

get

Operator function similar to operator.getitem but able to take a default value.

from ebbe import get

get([1, 2, 3], 1)
>>> 2

get([1, 2, 3], 4)
>>> None

# With default value
get([1, 2, 3], 4, 35)
>>> 35

getter

Operator factory similar to operator.itemgetter but able to take a default value.

from ebbe import getter

get_second_or_thirty = getter(1, 30)

get_second_or_thirty([1, 2, 3])
>>> 2

get_second_or_thirty([1])
>>> 30

# Overriding default on the spot
get_second_or_thirty([1], 76)
>>> 76

getpath

Operator function used to retrieve a value at given path in a nested structure or a default value if this value cannot be found.

from ebbe import getpath

data = {'a': {'b': [{'c': 34}, 'test'], 'd': 'hello'}}

getpath(data, ['a', 'b', 0, 'c'])
>>> 34

getpath(data, ['t', 'e', 's', 't'])
>>> None

# Using a default return value
getpath(data, ['t', 'e', 's', 't'], 45)
>>> 45

# Using a string path
getpath(data, 'a.b.d', split_char='.')
>>> 'hello'

Arguments

• target any: target object.
• path iterable: path to get.
• default ?any [None]: default value to return.
• items ?bool [True]: whether to attempt to traverse keys and indices.
• attributes ?bool [False]: whether to attempt to traverse attributes.
• split_char ?str: if given, will split strings passed as path instead of raising TypeError.
• parse_indices ?bool [False]: whether to parse integer indices when splitting string paths.

pathgetter

Function returning a getter function working as getpath and partially applied to use the provided path or paths.

from ebbe import pathgetter

data = {'a': {'b': [{'c': 34}, 'test'], 'd': 'hello'}}

getter = pathgetter(['a', 'b', 0, 'c'])
getter(data)
>>> 34

getter = pathgetter(['t', 'e', 's', 't'])
getter(data)
>>> None

# Using a default return value
getter = pathgetter(['t', 'e', 's', 't'])
getter(data, 45)
>>> 45

# Using a string path
getter = pathgetter('a.b.d', split_char='.')
getter(data)
>>> 'hello'

# Using multiple paths
getter = pathgetter(
  ['a', 'b', 0, 'c'],
  ['t', 'e', 's', 't'],
  ['a', 'b', 'd']
)
getter(data)
>>> (34, None, 'hello')

Arguments

• paths list: paths to get.
• items ?bool [True]: whether to attempt to traverse keys and indices.
• attributes ?bool [False]: whether to attempt to traverse attributes.
• split_char ?str: if given, will split strings passed as path instead of raising TypeError.
• parse_indices ?bool [False]: whether to parse integer indices when splitting string paths.

Getter arguments

• target any: target object.
• default ?any [None]: default value to return.

indexed

Function indexing the given iterable in a dict-like structure. This is basically just some functional sugar over a dict constructor.

from ebbe import indexed

indexed(range(3), key=lambda x: x * 10)
>>> {
  0: 0,
  10: 1,
  20: 2
}

grouped

Function grouping the given iterable by a key.

from ebbe import grouped

grouped(range(4), key=lambda x: x % 2)
>>> {
  0: [0, 2],
  1: [1, 3]
}

# Using an optional value
grouped(range(4), key=lambda x: x % 2, value=lambda x: x * 10)
>>> {
  0: [0, 20],
  1: [10, 30]
}

# Using the items variant
from ebbe import grouped_items

grouped_items((x % 2, x * 10) for i in range(4))
>>> {
  0: [0, 20],
  1: [10, 30]
}

partitioned

Function partitioning the given iterable by key.

from ebbe import partitioned

partitioned(range(4), key=lambda x: x % 2)
>>> [
  [0, 2],
  [1, 3]
]

# Using an optional value
partitioned(range(4), key=lambda x: x % 2, value=lambda x: x * 10)
>>> [
  [0, 20],
  [10, 30]
]

# Using the items variant
from ebbe import partitioned_items

partitioned_items((x % 2, x * 10) for i in range(4))
>>> [
  [0, 20],
  [10, 30]
]

sorted_uniq

Function sorting the given iterable then dropping its duplicate through a single linear pass over the data.

from ebbe import sorted_uniq

numbers = [3, 17, 3, 4, 1, 4, 5, 5, 1, -1, 5]
sorted_uniq(numbers)
>>> [-1, 1, 3, 4, 5, 17]

# It accepts all of `sorted` kwargs:
sorted_uniq(numbers, reverse=True)
>>> [17, 5, 4, 3, 1, -1]

pick

Function returning the given dictionary with only the selected keys.

from ebbe import pick

# Selected keys must be an iterable:
pick({'a': 1, 'b': 2, 'c': 3}, ['a', 'c'])
>>> {'a': 1, 'c': 3}

# If you need the function to raise if one of the picked keys is not found:
pick({'a': 1, 'b': 2, 'c': 3}, ['a', 'd'], strict=True)
>>> KeyError: 'd'

omit

Function returning the given dictionary without the selected keys.

from ebbe import omit

# Selected keys must be a container:
omit({'a': 1, 'b': 2, 'c': 3}, ['a', 'c'])
>>> {'b': 2}

# If need to select large numbers of keys, use a set:
omit({'a': 1, 'b': 2, 'c': 3}, {'a', 'c'})
>>> {'b': 2}

noop

Noop function (a function that can be called with any arguments and does nothing). Useful as a default to avoid complicating code sometimes.

from ebbe import noop

noop() # Does nothing...
noop(4, 5) # Still does nothing...
noop(4, index=65) # Nothing yet again...

compose

Function returning the composition function of its variadic arguments.

def times_2(x):
  return x * 2

def plus_5(x):
  return x + 5

compose(times_2, plus_5)(10)
>>> 30

# Reverse order
compose(times_2, plus_5, reverse=True)(10)
>>> 25

rcompose

Function returning the reverse composition function of its variadic arguments.

def times_2(x):
  return x * 2

def plus_5(x):
  return x + 5

rcompose(times_2, plus_5)(10)
>>> 25

and_join

Join function able to group the last items with a custom copula such as "and".

from ebbe import and_join

and_join(['1', '2', '3'])
>>> '1, 2 and 3'

and_join(['1', '2', '3'], separator=';', copula="y")
>>> '1; 2 y 3'

format_int

Format given number as an int with thousands separator.

from ebbe import format_int

format_int(4500)
>>> '4,500'

format_int(10000, separator=' ')
>>> '10 000'

format_time

Format time with custom precision and unit from years to nanoseconds.

from ebbe import format_time

format_time(57309)
>>> "57 microseconds and 309 nanoseconds"

format_time(57309, precision="microseconds")
>>> "57 microseconds

format_time(78, unit="seconds")
>>> "1 minute and 18 seconds"

format_time(4865268458795)
>>> "1 hour, 21 minutes, 5 seconds, 268 milliseconds, 458 microseconds and 795 nanoseconds"

assert format_time(4865268458795, max_items=2)
>>> "1 hour and 21 minutes"

format_time(4865268458795, short=True)
>>> "1h, 21m, 5s, 268ms, 458µs, 795ns"

decorators.fail_fast

Decorate a generator function by wrapping it into another generator function that will fail fast if some validation is run before executing the iteration logic so that exceptions can be caught early.

This logic is also available as a function.

from ebbe.decorators import fail_fast

def hellraiser(n):
  if n > 10:
    raise TypeError

  yield from range(n)

# This will not raise until you consume `gen`
gen = hellraiser(15)

@fail_fast()
def hellraiser(n):
  if n > 10:
    raise TypeError

  yield from range(n)

# This will raise immediately
gen = hellraiser(15)

decorators.with_defer

Decorates a function calling it with a defer kwarg working a bit like Go's defer statement so that you can "defer" actions to be done by the end of the function or when an exception is raised to cleanup or tear down things.

This relies on an ExitStack and can of course be also accomplished by context managers but this way of declaring things to defer can be useful sometimes to avoid nesting in complex functions.

from ebbe.decorators import with_defer

@with_defer()
def main(content, *, defer):
  f = open('./output.txt', 'w')
  defer(f.close)

  f.write(content)

Timer

Context manager printing the time (to stderr by default) it took to execute wrapped code. Very useful to run benchmarks.

from ebbe import Timer

with Timer():
  some_costly_operation()
# Will print "Timer: ...s etc." on exit

# To display a custom message:
with Timer('my operation'):
  ...

# To print to stdout
import sys

with Timer(file=sys.stdout):
  ...