equate

Equate

This is a package with tools for matching things.

Dirty things like language, files in your file system, socks and whistles.

Install

pip install equate

Moving on...

Little peep

Merging/joining tables is very common instance, yet only a small part of what is possible, and often needed. Consider the following use cases:

• Find the columns to match (join keys) by comparing how well the values of the column match.

• Comparing the values of the columns with something more flexible than hard equality. For example, correlation, similarity, etc.

• Find near duplicate columns

• Find rows to align, based on flexible comparison of fuzzily matched cells

Simple case

Say you have two sets of strings, and all you do is want to is match each element of the "keys" set to an element of the "values" set (never reusing the same value for a different key), and say you know that a matching value string will differ from its key only by a few characters. In that case just do this:

keys = ['apple', 'banana', 'carrot']
values = ['car', 'app', 'carob', 'cabana']
dict(match_greedily(keys, values))
# == {'apple': 'app', 'banana': 'cabana', 'carrot': 'carob'}

Note that by default, match_greedily uses the edit-distance as its score_func, and you can specify your own custom score_func. But the matching is done "greedily". This means that at every step, the highest-score value will be taken as the match. Some times this is not ideal (typically, your matches validity will decline along with the number of keys matched).

More involved methods

Here's a more involved entry point:

from equate import match_keys_to_values

keys = ['apple pie', 'apple crumble', 'banana split']
values = ['american pie', 'big apple', 'american girl', 'banana republic']
dict(match_keys_to_values(keys, values))
# == {'apple pie': 'american pie',
# 'apple crumble': 'big apple',
# 'banana split': 'banana republic'}

The algorithm that gets you these matches is a bit more involved, and parametrizable. This is how it works.

First, it computes a similarity matrix, and then applies a "matcher" that will search through this similarity matrix for an optimal matching, using any optimal search function you want (and of course, we provide a few standard ones).

The similarity matrix, if full, contains scores for every possible combination of keys and values. You can specify how to compute this similarity matrix, which means that if you don't want to compute the similarity for every combination, you don't need to. Usually, your similarity matrix will be a "sparse matrix", that is, only specify a few non-zero entries.

The default similarity matrix function uses a obj_to_vect function along with a vector similarity function similarty_func to compute what the score_func did in our first match_greedily function. By default here, though, similarity_matrix will use methods that are more powerful than just an edit-distance. It will learn and use a "TfIdf" vectorization (a.k.a. embedding) and a cosine similarity function. As a result, you should get finer matchings.

from equate import similarity_matrix

keys = ['apple pie', 'apple crumble', 'banana split']
values = ['american pie', 'big apple', 'american girl', 'banana republic']
m = similarity_matrix(keys, values)
m.round(2).tolist()
# == [[0.54, 0.38, 0.0, 0.0], [0.0, 0.33, 0.0, 0.0], [0.0, 0.0, 0.0, 0.41]]

The equate.util module has a few optimal matching function you can use from there to extract the matching pairs from the matrix. At the time of writing this, we've implemented: greedy_matching, hungarian_matching, maximal_matching, stable_marriage_matching, and kuhn_munkres_matching.

At the time of writing this, the default matcher used by match_keys_to_values is hungarian_matching.

An example: In search of a import-to-package name matcher

Here, we'll go through an actual practical example of when you might want to match things: "Guessing" the pip install name from a pip package name, and other related analyses.

The problem

Ever got an import error and wondered what the pip install package name was.

Say...

ImportError: No module named skimage

But it ain't pip install skimage is it (well, it USED to not to, but you get the point...). What you actually need to do to install (with pip) is:

pip install scikit-image

I would have guessed that!

So no, it's annoying. It shouldn't be allowed. And since it is, there should be an index out there to help out, right?

pip install --just-find-it-for-me skimage

Instead of just complaining, I thought I'd throw some code at it. (I'll still complain though.)

Here's a solution: Ask the world (of semantic clouds -- otherwise known as "Google") about it...

A (fun) solution

import requests
import re
from collections import Counter

search_re = re.compile('(?<=pip install\W)[-\w]+')

def pkg_name_options(query):
    r = requests.get('https://www.google.com/search', params={'q': f'python "pip install" {query}'})
    if r.status_code == 200:
        return Counter(filter(lambda x: x != query, p.findall(r.content.decode('latin-1')))).most_common()
    
def best_guess(query):
    t = pkg_name_options(query)
    if t:
        return t[0][0]
        

>>> pkg_name_options('skimage')
[('scikit-image', 5),
 ('-e', 2),
 ('virtualenv', 1),
 ('scikit', 1),
 ('scikit-', 1),
 ('pillow', 1)]

>>> best_guess('skimage')
'scikit-image'

Yay, it works! With a sample of one! Let's try two...

>>> pkg_name_options('sklearn')
[('numpy', 3), ('scikit-learn', 2), ('-U', 2), ('scikit-', 1), ('scipy', 1)]

Okay, so it already fails.

Sure, I could parse more carefully. I could dig into the webpages and get more scope.

That'd be fun.

But that's not very nice too Google (and probably is illegal, if anyone cares).

What you'll find next is an attempt to look at the man in the mirror instead. Looking locally, where the packages actually are: In the site-packages folders...

Extract, analyze and compare site-packages info names

import pandas as pd
import numpy as np

from equate.examples.site_names import (
    DFLT_SITE_PKG_DIR,    
    site_packages_info_df,
    print_n_null_elements_in_each_column_containing_at_least_one,
    Lidx,
)

>>> DFLT_SITE_PKG_DIR
'~/.virtualenvs/382/lib/python3.8/site-packages'

>>> data = site_packages_info_df()
>>> print(f"{data.shape}")
(303, 8)
>>> data

.dataframe tbody tr th:only-of-type { vertical-align: middle; } .dataframe tbody tr th { vertical-align: top; } .dataframe thead th { text-align: right; }

	dist_info_dirname	info_kind	dist_name	most_frequent_record_dirname	first_line_of_top_level_txt	installer	metadata_name	pypi_url_name
0	xlrd-1.2.0.dist-info	dist-info	xlrd	xlrd	xlrd	pip	xlrd	None
1	boltons-20.2.0.dist-info	dist-info	boltons	boltons	boltons	pip	boltons	None
2	appdirs-1.4.3.dist-info	dist-info	appdirs	appdirs	appdirs	pip	appdirs	None
3	yapf-0.29.0.dist-info	dist-info	yapf	yapftests	yapf	pip	yapf	None
4	cmudict-0.4.4.dist-info	dist-info	cmudict	cmudict	cmudict	pip	cmudict	None
...	...	...	...	...	...	...	...	...
298	simplegeneric-0.8.1.dist-info	dist-info	simplegeneric	simplegeneric	simplegeneric	pip	simplegeneric	None
299	plotly-4.6.0.dist-info	dist-info	plotly	plotly	_plotly_future_	pip	plotly	None
300	rsa-3.4.2.dist-info	dist-info	rsa	rsa	rsa	pip	rsa	None
301	backcall-0.1.0.dist-info	dist-info	backcall	backcall	backcall	pip	backcall	None
302	cantools-33.1.1.dist-info	dist-info	cantools	cantools	cantools	pip	cantools	None

303 rows × 8 columns

>>> print_n_null_elements_in_each_column_containing_at_least_one(data)
most_frequent_record_dirname:	1 null values
first_line_of_top_level_txt:	6 null values
installer:	32 null values
metadata_name:	1 null values
pypi_url_name:	255 null values

>>> lidx = Lidx(data)
>>> df = data[lidx.no_nans]
>>> print(f"no nan df: {len(df)=}")
no_nans: 302
equal: 187
dash_underscore_eq: 220
('equal', 'dash_underscore_eq'): 186

>>> lidx = Lidx(df)
>>> lidx.print_diagnosis()
no_nans: 302
equal: 187
dash_underscore_eq: 220
('equal', 'dash_underscore_eq'): 186

>>> lidx = Lidx(df, 'first_line_of_top_level_txt')
>>> lidx.print_diagnosis()
no_nans: 297
equal: 182
dash_underscore_eq: 214
('equal', 'dash_underscore_eq'): 181

>>> t = Lidx(df, 'most_frequent_record_dirname')
>>> tt = Lidx(df, 'first_line_of_top_level_txt')
>>> sum(t.equal | tt.equal)
199

>> sum(t.dash_underscore_eq | tt.dash_underscore_eq)
233