jk 0.1.0

each_cons

• each_cons(sequence, size)

Iterates lazily through a sequence, yielding a sliding window with the given size for each iteration.

Examples:

Calculating quarterly sales report:

>>> import jk
>>> month_sales = [123.45, 54.3, 428.1, 144.2, 245.45, 197.3]
>>> for a, b, c in jk.each_cons(month_sales, 3):
...     print '%0.2f' % ((a + b + c)/3)
...
201.95
208.87
272.58
195.65

Find duplicated lines in a file:

>>> lines = """here is a simple
... file for us to test.
... this line repeats
... this line repeats
... -- this one does not
... this one repeats too
... this one repeats too
... okay, we're done here""".split('\n')
>>>
>>> for ln, (a, b) in enumerate(jk.each_cons(lines, 2), 1):
...     if a == b:
...         print (ln, a)
...
(3, 'this line repeats')
(6, 'this one repeats too')

slice_before and slice_after

• slice_before(predicate, sequence)

• slice_after(predicate, sequence)

These functions are useful when you have a stream that has some sort of delimiter. Handy for parsing log files, for example.

They iterate lazily through a sequence, yielding a tuple containing the elements sliced just before (or after) the predicate evaluates to True.

The predicate argument can also be a string or a regular expression pattern to be matched against the sequence elements.

Examples:

Grouping numbers until reaching zero:

>>> numbers = [1, 2, 3, 0, 4, 5, 0, 6, 0, 7, 8]
>>> print list(jk.slice_after(lambda x: x == 0, numbers))
[(1, 2, 3, 0), (4, 5, 0), (6, 0), (7, 8)]

Reading entries of a fantasy multiline log file:

>>> log_lines = """START: initiating...
... kernel found
... EVENT: started
... moving on
... EVENT: something happened
... EVENT: another thing happened""".split('\n')
>>>
>>> for entry in jk.slice_before('^(START|EVENT):', log_lines):
...     print entry
...
('START: initiating...', 'kernel found')
('EVENT: started', 'moving on')
('EVENT: something happened',)
('EVENT: another thing happened',)

first, second and nth

• first(sequence, default=None)

Returns the first element of a sequence (or a default value if the sequence is empty).

• second(sequence, default=None)

Returns the second element of a sequence (or a default value if not exists).

• nth(sequence, n, default=None)

Returns the nth element of a sequence (or a default value if not exists).

Note that the argument n is not a zero-based index: it is a ordinal number, so n=1 means the first element, n=4 means the fourth and so on.