extratools 0.3.4

Extra Functional Tools beyond Standard and Third-Party Libraries

Extra functional tools that go beyond standard libraries itertools, functools, etc. and popular third-party libraries like toolz and fancy.

• Like toolz, most of the tools are designed to be efficient, pure, and lazy.

This library is under active development, and new functions will be added on regular basis.

• Any idea or contribution is highly welcome.

Installation

This package is available on PyPi. Just use pip3 install -U extratools to install it.

Available Tools

Please check individual source file for details.

seqtools

Tools for matching sequences (including strings), with or without gaps allowed between matching items. Note that empty sequence is always a sub-sequence of any other sequence.

• findsubseq(a, b) returns the first position where a is a sub-sequence of b, or -1 when not found.

• issubseq(a, b) checks if a is a sub-sequence of b.

• findsubseqwithgap(a, b) returns the matching positions where a is a sub-sequence of b, where gaps are allowed, or None when not found.

• issubseqwithgap(a, b) checks if a is a sub-sequence of b, where gaps are allowed.

Tools for comparing sequences (including strings).

• productcmp(x, y) compares two sequences x and y with equal length according to product order. Returns -1 if smaller, 0 if equal, 1 if greater, and None if not comparable.

  • Throw exception if x and y have different lengths.

Tools for sorting sequences.

• sortedbyrank(data, ranks, reverse=False) returns the sorted list of data, according to the respective rank of each individual element in ranks.

Tools for encoding/decoding sequences.

• compress(data, key=None) compresses the sequence by encoding continuous identical Item to (Item, Count), according to run-length encoding.

  • Different from itertools.compress.

list(compress([1, 2, 2, 3, 3, 3, 4, 4, 4, 4]))
# [(1, 1), (2, 2), (3, 3), (4, 4)]

• decompress(data) decompresses the sequence by decoding (Item, Count) to continuous identical Item, according to run-length encoding.

• todeltas(data, op=operator.sub) compresses the sequence by encoding the difference between previous and current items, according to delta encoding.

  • For custom type of item, either define the - operator or specify the op function computing the difference.

list(todeltas([1, 2, 2, 3, 3, 3, 4, 4, 4, 4]))
# [1, 1, 0, 1, 0, 0, 1, 0, 0, 0]

• fromdeltas(data, op=operator.add) decompresses the sequence by decoding the difference between previous and current items, according to delta encoding.

  • For custom type of item, either define the + operator or specify the op function merging the difference.

sortedtools

Tools for sorted sequences.

• sortedcommon(a, b, key=None) returns the common elements between a and b.

  • When both a and b are sorted sets with no duplicate element, equal to sorted(set(a) & set(b)) but more efficient.

• sortedalone(a, b, key=None) returns the elements not in both a and b.

  • When both a and b are sorted sets with no duplicate element, equal to sorted((set(a) | set(b)) - (set(a) & set(b))) but more efficient.

• sorteddiff(a, b, key=None) returns the elements only in a and not in b.

  • When both a and b are sorted sets with no duplicate element, equal to sorted(set(a) - set(b)) but more efficient.

• issubsorted(a, b, key=None) checks if a is a sorted sub-sequence of b.

  • When both a and b are sorted sets with no duplicate element, equal to set(a) <= set(b) but more efficient.

strtools

Tools for strings.

• str2grams(s, n, pad=None) returns the ordered n-grams of string s.

  • Optional padding at the start and end can be added by specifying pad. \0 is usually a safe choice for pad when not displaying.

• tagstats(tags, lines, separator=None) efficiently computes the number of lines containing each tag.

  • TagStats is used to compute efficiently, where the common prefixes among tags are matched only once.

  • separator is a regex to tokenize each string. In default when separator is None, each string is not tokenized.

tagstats(
    ["a b", "a c", "b c"],
    ["a b c", "b c d", "c d e"]
)
# {'a b': 1, 'a c': 0, 'b c': 2}

dicttools

Tools for inverting dictionaries.

• invertdict(d) inverts (Key, Value) pairs to (Value, Key).

  • If multiple keys share the same value, the inverted directory keeps last of the respective keys.

• invertdict_multiple(d) inverts (Key, List[Value]) pairs to (Value, Key).

  • If multiple keys share the same value, the inverted directory keeps last of the respective keys.

• invertdict_safe(d) inverts (Key, Value) pairs to (Value, List[Key]).

  • If multiple keys share the same value, the inverted directory keeps a list of all the respective keys.

Tools for remapping elements.

• remap(data, mapping, key=None) remaps each unique element in data according to function key.

  • mapping is a dictionary recording all the mappings, optionally containing previous mappings to reuse.

  • In default, key returns integers starting from 0.

wordmap = {}
db = [list(remap(doc, wordmap)) for doc in docs]

settools

Tools for set operations.

• addtoset(s, x) checks whether adding x to set s is successful.

Tools for set similarities.

• jaccard(a, b) computes the Jaccard similarity between two sets a and b.

• multisetjaccard(a, b) computes the Jaccard similarity between two multi-sets (Counters) a and b.

• weightedjaccard(a, b, key=sum) computes the weighted Jaccard similarity between two sets a and b, using function key to compute the total weight of the elements within a set.

tabletools

Tools for tables.

• transpose(data) returns the transpose of table data, i.e., switch rows and columns.

  • Useful to switch table data from row-based to column-based and backwards.

transpose([
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
])
# [[1, 4, 7],
#  [2, 5, 8],
#  [3, 6, 9]]

mathtools

Tools for math.

• safediv(a, b) avoids the division by zero exception, by returning infinite with proper sign.

  • Closely referring IEEE Standard 754.

stattools

Tools for statistics.

• medianabsdev(data) computes the median absolute deviation of a list of floats.

• entropy(data) computes the entropy of a list of any items.

  • You can also pass a dictionary of (item, frequency) as frequency distribution to data.

• histogram(thresholds, data) computes the histogram over all the floats in data.

  • The search space is divided by the thresholds of bins specified in thresholds.

  • Each bin of the histogram is labelled by its lower threshold.

    • All values in the bin are no less than the current threshold and less than the next threshold.

    • The first bin is always labelled by -infinity.

histogram(
    [0.1, 0.5, 0.8, 0.9],
    [0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1]
)
# {-inf: 1, 0.1: 4, 0.5: 3, 0.8: 1, 0.9: 2}

misctools

Tools for miscellaneous purposes.

• cmp(a, b) restores the useful cmp function previously in Python 2.

  • Implemented according to What's New in Python 3.0.

disjointsets

Disjoint sets with path compression, based a lot on this implementation. After d = DisjointSets():

• d.add(x) adds a new disjoint set containing x.

• d[x] returns the representing element of the disjoint set containing x.

• d.disjoints() returns all the representing elements and their respective disjoint sets.

• d.union(*xs) union all the elements in xs into a single disjoint set.

printtools

Tools for non-functional but useful printing purposes.

• print2(*args, **kwargs) redirects the output of print to standard error.

  • The same parameters are accepted.